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1 | gitcore-tutorial(7) |
2 | =================== | |
927a503c | 3 | |
497c8331 CC |
4 | NAME |
5 | ---- | |
6 | gitcore-tutorial - A git core tutorial for developers | |
7 | ||
8 | SYNOPSIS | |
9 | -------- | |
10 | git * | |
11 | ||
12 | DESCRIPTION | |
13 | ----------- | |
927a503c | 14 | |
a85fecaf BF |
15 | This tutorial explains how to use the "core" git programs to set up and |
16 | work with a git repository. | |
927a503c | 17 | |
a85fecaf | 18 | If you just need to use git as a revision control system you may prefer |
6998e4db JN |
19 | to start with "A Tutorial Introduction to GIT" (linkgit:gittutorial[7]) or |
20 | link:user-manual.html[the GIT User Manual]. | |
a85fecaf BF |
21 | |
22 | However, an understanding of these low-level tools can be helpful if | |
23 | you want to understand git's internals. | |
927a503c BF |
24 | |
25 | The core git is often called "plumbing", with the prettier user | |
26 | interfaces on top of it called "porcelain". You may not want to use the | |
27 | plumbing directly very often, but it can be good to know what the | |
28 | plumbing does for when the porcelain isn't flushing. | |
29 | ||
927a503c | 30 | [NOTE] |
a85fecaf BF |
31 | Deeper technical details are often marked as Notes, which you can |
32 | skip on your first reading. | |
927a503c BF |
33 | |
34 | ||
35 | Creating a git repository | |
36 | ------------------------- | |
37 | ||
38 | Creating a new git repository couldn't be easier: all git repositories start | |
39 | out empty, and the only thing you need to do is find yourself a | |
40 | subdirectory that you want to use as a working tree - either an empty | |
41 | one for a totally new project, or an existing working tree that you want | |
a6080a0a | 42 | to import into git. |
927a503c BF |
43 | |
44 | For our first example, we're going to start a totally new repository from | |
ba020ef5 | 45 | scratch, with no pre-existing files, and we'll call it 'git-tutorial'. |
927a503c | 46 | To start up, create a subdirectory for it, change into that |
ba020ef5 | 47 | subdirectory, and initialize the git infrastructure with 'git-init': |
927a503c BF |
48 | |
49 | ------------------------------------------------ | |
50 | $ mkdir git-tutorial | |
51 | $ cd git-tutorial | |
b1889c36 | 52 | $ git init |
927a503c BF |
53 | ------------------------------------------------ |
54 | ||
55 | to which git will reply | |
56 | ||
57 | ---------------- | |
ef0a89a6 | 58 | Initialized empty Git repository in .git/ |
927a503c BF |
59 | ---------------- |
60 | ||
61 | which is just git's way of saying that you haven't been doing anything | |
62 | strange, and that it will have created a local `.git` directory setup for | |
63 | your new project. You will now have a `.git` directory, and you can | |
2fd02c92 | 64 | inspect that with 'ls'. For your new empty project, it should show you |
927a503c BF |
65 | three entries, among other things: |
66 | ||
960c7021 JH |
67 | - a file called `HEAD`, that has `ref: refs/heads/master` in it. |
68 | This is similar to a symbolic link and points at | |
69 | `refs/heads/master` relative to the `HEAD` file. | |
927a503c BF |
70 | + |
71 | Don't worry about the fact that the file that the `HEAD` link points to | |
72 | doesn't even exist yet -- you haven't created the commit that will | |
73 | start your `HEAD` development branch yet. | |
74 | ||
75 | - a subdirectory called `objects`, which will contain all the | |
76 | objects of your project. You should never have any real reason to | |
77 | look at the objects directly, but you might want to know that these | |
78 | objects are what contains all the real 'data' in your repository. | |
79 | ||
80 | - a subdirectory called `refs`, which contains references to objects. | |
81 | ||
82 | In particular, the `refs` subdirectory will contain two other | |
83 | subdirectories, named `heads` and `tags` respectively. They do | |
84 | exactly what their names imply: they contain references to any number | |
85 | of different 'heads' of development (aka 'branches'), and to any | |
86 | 'tags' that you have created to name specific versions in your | |
87 | repository. | |
88 | ||
89 | One note: the special `master` head is the default branch, which is | |
960c7021 | 90 | why the `.git/HEAD` file was created points to it even if it |
927a503c BF |
91 | doesn't yet exist. Basically, the `HEAD` link is supposed to always |
92 | point to the branch you are working on right now, and you always | |
93 | start out expecting to work on the `master` branch. | |
94 | ||
95 | However, this is only a convention, and you can name your branches | |
96 | anything you want, and don't have to ever even 'have' a `master` | |
97 | branch. A number of the git tools will assume that `.git/HEAD` is | |
98 | valid, though. | |
99 | ||
100 | [NOTE] | |
101 | An 'object' is identified by its 160-bit SHA1 hash, aka 'object name', | |
102 | and a reference to an object is always the 40-byte hex | |
103 | representation of that SHA1 name. The files in the `refs` | |
104 | subdirectory are expected to contain these hex references | |
105 | (usually with a final `\'\n\'` at the end), and you should thus | |
106 | expect to see a number of 41-byte files containing these | |
107 | references in these `refs` subdirectories when you actually start | |
108 | populating your tree. | |
109 | ||
110 | [NOTE] | |
6998e4db | 111 | An advanced user may want to take a look at linkgit:gitrepository-layout[5] |
927a503c BF |
112 | after finishing this tutorial. |
113 | ||
114 | You have now created your first git repository. Of course, since it's | |
115 | empty, that's not very useful, so let's start populating it with data. | |
116 | ||
117 | ||
118 | Populating a git repository | |
119 | --------------------------- | |
120 | ||
121 | We'll keep this simple and stupid, so we'll start off with populating a | |
122 | few trivial files just to get a feel for it. | |
123 | ||
124 | Start off with just creating any random files that you want to maintain | |
125 | in your git repository. We'll start off with a few bad examples, just to | |
126 | get a feel for how this works: | |
127 | ||
128 | ------------------------------------------------ | |
129 | $ echo "Hello World" >hello | |
130 | $ echo "Silly example" >example | |
131 | ------------------------------------------------ | |
132 | ||
960c7021 JH |
133 | you have now created two files in your working tree (aka 'working directory'), |
134 | but to actually check in your hard work, you will have to go through two steps: | |
927a503c BF |
135 | |
136 | - fill in the 'index' file (aka 'cache') with the information about your | |
137 | working tree state. | |
138 | ||
139 | - commit that index file as an object. | |
140 | ||
141 | The first step is trivial: when you want to tell git about any changes | |
ba020ef5 | 142 | to your working tree, you use the 'git-update-index' program. That |
927a503c BF |
143 | program normally just takes a list of filenames you want to update, but |
144 | to avoid trivial mistakes, it refuses to add new entries to the index | |
145 | (or remove existing ones) unless you explicitly tell it that you're | |
146 | adding a new entry with the `\--add` flag (or removing an entry with the | |
147 | `\--remove`) flag. | |
148 | ||
149 | So to populate the index with the two files you just created, you can do | |
150 | ||
151 | ------------------------------------------------ | |
b1889c36 | 152 | $ git update-index --add hello example |
927a503c BF |
153 | ------------------------------------------------ |
154 | ||
155 | and you have now told git to track those two files. | |
156 | ||
157 | In fact, as you did that, if you now look into your object directory, | |
158 | you'll notice that git will have added two new objects to the object | |
159 | database. If you did exactly the steps above, you should now be able to do | |
160 | ||
161 | ||
162 | ---------------- | |
163 | $ ls .git/objects/??/* | |
164 | ---------------- | |
165 | ||
166 | and see two files: | |
167 | ||
168 | ---------------- | |
a6080a0a | 169 | .git/objects/55/7db03de997c86a4a028e1ebd3a1ceb225be238 |
927a503c BF |
170 | .git/objects/f2/4c74a2e500f5ee1332c86b94199f52b1d1d962 |
171 | ---------------- | |
172 | ||
960c7021 JH |
173 | which correspond with the objects with names of `557db...` and |
174 | `f24c7...` respectively. | |
927a503c | 175 | |
ba020ef5 | 176 | If you want to, you can use 'git-cat-file' to look at those objects, but |
927a503c BF |
177 | you'll have to use the object name, not the filename of the object: |
178 | ||
179 | ---------------- | |
b1889c36 | 180 | $ git cat-file -t 557db03de997c86a4a028e1ebd3a1ceb225be238 |
927a503c BF |
181 | ---------------- |
182 | ||
ba020ef5 | 183 | where the `-t` tells 'git-cat-file' to tell you what the "type" of the |
abda1ef5 | 184 | object is. git will tell you that you have a "blob" object (i.e., just a |
927a503c BF |
185 | regular file), and you can see the contents with |
186 | ||
187 | ---------------- | |
b1889c36 | 188 | $ git cat-file "blob" 557db03 |
927a503c BF |
189 | ---------------- |
190 | ||
960c7021 | 191 | which will print out "Hello World". The object `557db03` is nothing |
927a503c BF |
192 | more than the contents of your file `hello`. |
193 | ||
194 | [NOTE] | |
195 | Don't confuse that object with the file `hello` itself. The | |
196 | object is literally just those specific *contents* of the file, and | |
197 | however much you later change the contents in file `hello`, the object | |
198 | we just looked at will never change. Objects are immutable. | |
199 | ||
200 | [NOTE] | |
201 | The second example demonstrates that you can | |
202 | abbreviate the object name to only the first several | |
203 | hexadecimal digits in most places. | |
204 | ||
205 | Anyway, as we mentioned previously, you normally never actually take a | |
206 | look at the objects themselves, and typing long 40-character hex | |
207 | names is not something you'd normally want to do. The above digression | |
ba020ef5 | 208 | was just to show that 'git-update-index' did something magical, and |
927a503c BF |
209 | actually saved away the contents of your files into the git object |
210 | database. | |
211 | ||
212 | Updating the index did something else too: it created a `.git/index` | |
213 | file. This is the index that describes your current working tree, and | |
214 | something you should be very aware of. Again, you normally never worry | |
215 | about the index file itself, but you should be aware of the fact that | |
216 | you have not actually really "checked in" your files into git so far, | |
217 | you've only *told* git about them. | |
218 | ||
219 | However, since git knows about them, you can now start using some of the | |
a6080a0a | 220 | most basic git commands to manipulate the files or look at their status. |
927a503c BF |
221 | |
222 | In particular, let's not even check in the two files into git yet, we'll | |
223 | start off by adding another line to `hello` first: | |
224 | ||
225 | ------------------------------------------------ | |
226 | $ echo "It's a new day for git" >>hello | |
227 | ------------------------------------------------ | |
228 | ||
229 | and you can now, since you told git about the previous state of `hello`, ask | |
230 | git what has changed in the tree compared to your old index, using the | |
ba020ef5 | 231 | 'git-diff-files' command: |
927a503c BF |
232 | |
233 | ------------ | |
b1889c36 | 234 | $ git diff-files |
927a503c BF |
235 | ------------ |
236 | ||
237 | Oops. That wasn't very readable. It just spit out its own internal | |
5833d730 | 238 | version of a 'diff', but that internal version really just tells you |
927a503c BF |
239 | that it has noticed that "hello" has been modified, and that the old object |
240 | contents it had have been replaced with something else. | |
241 | ||
ba020ef5 | 242 | To make it readable, we can tell 'git-diff-files' to output the |
927a503c BF |
243 | differences as a patch, using the `-p` flag: |
244 | ||
245 | ------------ | |
b1889c36 | 246 | $ git diff-files -p |
927a503c BF |
247 | diff --git a/hello b/hello |
248 | index 557db03..263414f 100644 | |
249 | --- a/hello | |
250 | +++ b/hello | |
251 | @@ -1 +1,2 @@ | |
252 | Hello World | |
253 | +It's a new day for git | |
254 | ---- | |
255 | ||
256 | i.e. the diff of the change we caused by adding another line to `hello`. | |
257 | ||
ba020ef5 | 258 | In other words, 'git-diff-files' always shows us the difference between |
927a503c BF |
259 | what is recorded in the index, and what is currently in the working |
260 | tree. That's very useful. | |
261 | ||
b1889c36 | 262 | A common shorthand for `git diff-files -p` is to just write `git |
927a503c BF |
263 | diff`, which will do the same thing. |
264 | ||
265 | ------------ | |
266 | $ git diff | |
267 | diff --git a/hello b/hello | |
268 | index 557db03..263414f 100644 | |
269 | --- a/hello | |
270 | +++ b/hello | |
271 | @@ -1 +1,2 @@ | |
272 | Hello World | |
273 | +It's a new day for git | |
274 | ------------ | |
275 | ||
276 | ||
277 | Committing git state | |
278 | -------------------- | |
279 | ||
280 | Now, we want to go to the next stage in git, which is to take the files | |
281 | that git knows about in the index, and commit them as a real tree. We do | |
282 | that in two phases: creating a 'tree' object, and committing that 'tree' | |
283 | object as a 'commit' object together with an explanation of what the | |
284 | tree was all about, along with information of how we came to that state. | |
285 | ||
ba020ef5 | 286 | Creating a tree object is trivial, and is done with 'git-write-tree'. |
483bc4f0 | 287 | There are no options or other input: `git write-tree` will take the |
927a503c BF |
288 | current index state, and write an object that describes that whole |
289 | index. In other words, we're now tying together all the different | |
290 | filenames with their contents (and their permissions), and we're | |
291 | creating the equivalent of a git "directory" object: | |
292 | ||
293 | ------------------------------------------------ | |
b1889c36 | 294 | $ git write-tree |
927a503c BF |
295 | ------------------------------------------------ |
296 | ||
297 | and this will just output the name of the resulting tree, in this case | |
298 | (if you have done exactly as I've described) it should be | |
299 | ||
300 | ---------------- | |
301 | 8988da15d077d4829fc51d8544c097def6644dbb | |
302 | ---------------- | |
303 | ||
304 | which is another incomprehensible object name. Again, if you want to, | |
b1889c36 | 305 | you can use `git cat-file -t 8988d\...` to see that this time the object |
927a503c | 306 | is not a "blob" object, but a "tree" object (you can also use |
b1889c36 | 307 | `git cat-file` to actually output the raw object contents, but you'll see |
927a503c BF |
308 | mainly a binary mess, so that's less interesting). |
309 | ||
ba020ef5 | 310 | However -- normally you'd never use 'git-write-tree' on its own, because |
927a503c | 311 | normally you always commit a tree into a commit object using the |
ba020ef5 JN |
312 | 'git-commit-tree' command. In fact, it's easier to not actually use |
313 | 'git-write-tree' on its own at all, but to just pass its result in as an | |
314 | argument to 'git-commit-tree'. | |
927a503c | 315 | |
ba020ef5 | 316 | 'git-commit-tree' normally takes several arguments -- it wants to know |
927a503c BF |
317 | what the 'parent' of a commit was, but since this is the first commit |
318 | ever in this new repository, and it has no parents, we only need to pass in | |
ba020ef5 | 319 | the object name of the tree. However, 'git-commit-tree' also wants to get a |
79dbbedd LFC |
320 | commit message on its standard input, and it will write out the resulting |
321 | object name for the commit to its standard output. | |
927a503c BF |
322 | |
323 | And this is where we create the `.git/refs/heads/master` file | |
324 | which is pointed at by `HEAD`. This file is supposed to contain | |
325 | the reference to the top-of-tree of the master branch, and since | |
ba020ef5 | 326 | that's exactly what 'git-commit-tree' spits out, we can do this |
927a503c BF |
327 | all with a sequence of simple shell commands: |
328 | ||
329 | ------------------------------------------------ | |
b1889c36 JN |
330 | $ tree=$(git write-tree) |
331 | $ commit=$(echo 'Initial commit' | git commit-tree $tree) | |
332 | $ git update-ref HEAD $commit | |
927a503c BF |
333 | ------------------------------------------------ |
334 | ||
ebd124c6 NP |
335 | In this case this creates a totally new commit that is not related to |
336 | anything else. Normally you do this only *once* for a project ever, and | |
337 | all later commits will be parented on top of an earlier commit. | |
927a503c BF |
338 | |
339 | Again, normally you'd never actually do this by hand. There is a | |
340 | helpful script called `git commit` that will do all of this for you. So | |
341 | you could have just written `git commit` | |
342 | instead, and it would have done the above magic scripting for you. | |
343 | ||
344 | ||
345 | Making a change | |
346 | --------------- | |
347 | ||
ba020ef5 | 348 | Remember how we did the 'git-update-index' on file `hello` and then we |
927a503c | 349 | changed `hello` afterward, and could compare the new state of `hello` with the |
a6080a0a | 350 | state we saved in the index file? |
927a503c | 351 | |
ba020ef5 | 352 | Further, remember how I said that 'git-write-tree' writes the contents |
927a503c BF |
353 | of the *index* file to the tree, and thus what we just committed was in |
354 | fact the *original* contents of the file `hello`, not the new ones. We did | |
355 | that on purpose, to show the difference between the index state, and the | |
356 | state in the working tree, and how they don't have to match, even | |
357 | when we commit things. | |
358 | ||
b1889c36 | 359 | As before, if we do `git diff-files -p` in our git-tutorial project, |
927a503c BF |
360 | we'll still see the same difference we saw last time: the index file |
361 | hasn't changed by the act of committing anything. However, now that we | |
362 | have committed something, we can also learn to use a new command: | |
ba020ef5 | 363 | 'git-diff-index'. |
927a503c | 364 | |
ba020ef5 JN |
365 | Unlike 'git-diff-files', which showed the difference between the index |
366 | file and the working tree, 'git-diff-index' shows the differences | |
927a503c | 367 | between a committed *tree* and either the index file or the working |
ba020ef5 | 368 | tree. In other words, 'git-diff-index' wants a tree to be diffed |
927a503c | 369 | against, and before we did the commit, we couldn't do that, because we |
a6080a0a | 370 | didn't have anything to diff against. |
927a503c BF |
371 | |
372 | But now we can do | |
373 | ||
374 | ---------------- | |
b1889c36 | 375 | $ git diff-index -p HEAD |
927a503c BF |
376 | ---------------- |
377 | ||
ba020ef5 | 378 | (where `-p` has the same meaning as it did in 'git-diff-files'), and it |
a6080a0a | 379 | will show us the same difference, but for a totally different reason. |
927a503c BF |
380 | Now we're comparing the working tree not against the index file, |
381 | but against the tree we just wrote. It just so happens that those two | |
382 | are obviously the same, so we get the same result. | |
383 | ||
384 | Again, because this is a common operation, you can also just shorthand | |
385 | it with | |
386 | ||
387 | ---------------- | |
388 | $ git diff HEAD | |
389 | ---------------- | |
390 | ||
391 | which ends up doing the above for you. | |
392 | ||
ba020ef5 | 393 | In other words, 'git-diff-index' normally compares a tree against the |
927a503c BF |
394 | working tree, but when given the `\--cached` flag, it is told to |
395 | instead compare against just the index cache contents, and ignore the | |
396 | current working tree state entirely. Since we just wrote the index | |
b1889c36 | 397 | file to HEAD, doing `git diff-index \--cached -p HEAD` should thus return |
a6080a0a | 398 | an empty set of differences, and that's exactly what it does. |
927a503c BF |
399 | |
400 | [NOTE] | |
401 | ================ | |
ba020ef5 | 402 | 'git-diff-index' really always uses the index for its |
927a503c BF |
403 | comparisons, and saying that it compares a tree against the working |
404 | tree is thus not strictly accurate. In particular, the list of | |
405 | files to compare (the "meta-data") *always* comes from the index file, | |
406 | regardless of whether the `\--cached` flag is used or not. The `\--cached` | |
407 | flag really only determines whether the file *contents* to be compared | |
408 | come from the working tree or not. | |
409 | ||
410 | This is not hard to understand, as soon as you realize that git simply | |
411 | never knows (or cares) about files that it is not told about | |
412 | explicitly. git will never go *looking* for files to compare, it | |
413 | expects you to tell it what the files are, and that's what the index | |
414 | is there for. | |
415 | ================ | |
416 | ||
417 | However, our next step is to commit the *change* we did, and again, to | |
418 | understand what's going on, keep in mind the difference between "working | |
419 | tree contents", "index file" and "committed tree". We have changes | |
420 | in the working tree that we want to commit, and we always have to | |
421 | work through the index file, so the first thing we need to do is to | |
422 | update the index cache: | |
423 | ||
424 | ------------------------------------------------ | |
b1889c36 | 425 | $ git update-index hello |
927a503c BF |
426 | ------------------------------------------------ |
427 | ||
428 | (note how we didn't need the `\--add` flag this time, since git knew | |
429 | about the file already). | |
430 | ||
ba020ef5 | 431 | Note what happens to the different 'git-diff-\*' versions here. After |
b1889c36 JN |
432 | we've updated `hello` in the index, `git diff-files -p` now shows no |
433 | differences, but `git diff-index -p HEAD` still *does* show that the | |
927a503c | 434 | current state is different from the state we committed. In fact, now |
ba020ef5 | 435 | 'git-diff-index' shows the same difference whether we use the `--cached` |
927a503c BF |
436 | flag or not, since now the index is coherent with the working tree. |
437 | ||
438 | Now, since we've updated `hello` in the index, we can commit the new | |
439 | version. We could do it by writing the tree by hand again, and | |
440 | committing the tree (this time we'd have to use the `-p HEAD` flag to | |
441 | tell commit that the HEAD was the *parent* of the new commit, and that | |
442 | this wasn't an initial commit any more), but you've done that once | |
443 | already, so let's just use the helpful script this time: | |
444 | ||
445 | ------------------------------------------------ | |
446 | $ git commit | |
447 | ------------------------------------------------ | |
448 | ||
449 | which starts an editor for you to write the commit message and tells you | |
450 | a bit about what you have done. | |
451 | ||
452 | Write whatever message you want, and all the lines that start with '#' | |
453 | will be pruned out, and the rest will be used as the commit message for | |
454 | the change. If you decide you don't want to commit anything after all at | |
455 | this point (you can continue to edit things and update the index), you | |
456 | can just leave an empty message. Otherwise `git commit` will commit | |
457 | the change for you. | |
458 | ||
459 | You've now made your first real git commit. And if you're interested in | |
460 | looking at what `git commit` really does, feel free to investigate: | |
461 | it's a few very simple shell scripts to generate the helpful (?) commit | |
462 | message headers, and a few one-liners that actually do the | |
ba020ef5 | 463 | commit itself ('git-commit'). |
927a503c BF |
464 | |
465 | ||
466 | Inspecting Changes | |
467 | ------------------ | |
468 | ||
469 | While creating changes is useful, it's even more useful if you can tell | |
470 | later what changed. The most useful command for this is another of the | |
5833d730 | 471 | 'diff' family, namely 'git-diff-tree'. |
927a503c | 472 | |
ba020ef5 | 473 | 'git-diff-tree' can be given two arbitrary trees, and it will tell you the |
927a503c BF |
474 | differences between them. Perhaps even more commonly, though, you can |
475 | give it just a single commit object, and it will figure out the parent | |
476 | of that commit itself, and show the difference directly. Thus, to get | |
477 | the same diff that we've already seen several times, we can now do | |
478 | ||
479 | ---------------- | |
b1889c36 | 480 | $ git diff-tree -p HEAD |
927a503c BF |
481 | ---------------- |
482 | ||
483 | (again, `-p` means to show the difference as a human-readable patch), | |
484 | and it will show what the last commit (in `HEAD`) actually changed. | |
485 | ||
486 | [NOTE] | |
487 | ============ | |
488 | Here is an ASCII art by Jon Loeliger that illustrates how | |
489 | various diff-\* commands compare things. | |
490 | ||
491 | diff-tree | |
492 | +----+ | |
493 | | | | |
494 | | | | |
495 | V V | |
496 | +-----------+ | |
497 | | Object DB | | |
498 | | Backing | | |
499 | | Store | | |
500 | +-----------+ | |
501 | ^ ^ | |
502 | | | | |
503 | | | diff-index --cached | |
504 | | | | |
505 | diff-index | V | |
506 | | +-----------+ | |
507 | | | Index | | |
508 | | | "cache" | | |
509 | | +-----------+ | |
510 | | ^ | |
511 | | | | |
512 | | | diff-files | |
513 | | | | |
514 | V V | |
515 | +-----------+ | |
516 | | Working | | |
517 | | Directory | | |
518 | +-----------+ | |
519 | ============ | |
520 | ||
ba020ef5 | 521 | More interestingly, you can also give 'git-diff-tree' the `--pretty` flag, |
960c7021 | 522 | which tells it to also show the commit message and author and date of the |
927a503c BF |
523 | commit, and you can tell it to show a whole series of diffs. |
524 | Alternatively, you can tell it to be "silent", and not show the diffs at | |
525 | all, but just show the actual commit message. | |
526 | ||
ba020ef5 JN |
527 | In fact, together with the 'git-rev-list' program (which generates a |
528 | list of revisions), 'git-diff-tree' ends up being a veritable fount of | |
529 | changes. A trivial (but very useful) script called 'git-whatchanged' is | |
927a503c BF |
530 | included with git which does exactly this, and shows a log of recent |
531 | activities. | |
532 | ||
533 | To see the whole history of our pitiful little git-tutorial project, you | |
534 | can do | |
535 | ||
536 | ---------------- | |
537 | $ git log | |
538 | ---------------- | |
539 | ||
540 | which shows just the log messages, or if we want to see the log together | |
541 | with the associated patches use the more complex (and much more | |
542 | powerful) | |
543 | ||
544 | ---------------- | |
b1889c36 | 545 | $ git whatchanged -p |
927a503c BF |
546 | ---------------- |
547 | ||
548 | and you will see exactly what has changed in the repository over its | |
a6080a0a | 549 | short history. |
927a503c BF |
550 | |
551 | [NOTE] | |
abea85d1 CR |
552 | When using the above two commands, the initial commit will be shown. |
553 | If this is a problem because it is huge, you can hide it by setting | |
554 | the log.showroot configuration variable to false. Having this, you | |
555 | can still show it for each command just adding the `\--root` option, | |
ba020ef5 | 556 | which is a flag for 'git-diff-tree' accepted by both commands. |
927a503c BF |
557 | |
558 | With that, you should now be having some inkling of what git does, and | |
559 | can explore on your own. | |
560 | ||
561 | [NOTE] | |
562 | Most likely, you are not directly using the core | |
ba020ef5 | 563 | git Plumbing commands, but using Porcelain such as 'git-add', `git-rm' |
3b27428b | 564 | and `git-commit'. |
927a503c BF |
565 | |
566 | ||
567 | Tagging a version | |
568 | ----------------- | |
569 | ||
570 | In git, there are two kinds of tags, a "light" one, and an "annotated tag". | |
571 | ||
572 | A "light" tag is technically nothing more than a branch, except we put | |
573 | it in the `.git/refs/tags/` subdirectory instead of calling it a `head`. | |
574 | So the simplest form of tag involves nothing more than | |
575 | ||
576 | ------------------------------------------------ | |
577 | $ git tag my-first-tag | |
578 | ------------------------------------------------ | |
579 | ||
580 | which just writes the current `HEAD` into the `.git/refs/tags/my-first-tag` | |
581 | file, after which point you can then use this symbolic name for that | |
582 | particular state. You can, for example, do | |
583 | ||
584 | ---------------- | |
585 | $ git diff my-first-tag | |
586 | ---------------- | |
587 | ||
5221ecbc | 588 | to diff your current state against that tag which at this point will |
927a503c BF |
589 | obviously be an empty diff, but if you continue to develop and commit |
590 | stuff, you can use your tag as an "anchor-point" to see what has changed | |
591 | since you tagged it. | |
592 | ||
593 | An "annotated tag" is actually a real git object, and contains not only a | |
594 | pointer to the state you want to tag, but also a small tag name and | |
595 | message, along with optionally a PGP signature that says that yes, | |
596 | you really did | |
597 | that tag. You create these annotated tags with either the `-a` or | |
ba020ef5 | 598 | `-s` flag to 'git-tag': |
927a503c BF |
599 | |
600 | ---------------- | |
601 | $ git tag -s <tagname> | |
602 | ---------------- | |
603 | ||
604 | which will sign the current `HEAD` (but you can also give it another | |
abda1ef5 | 605 | argument that specifies the thing to tag, i.e., you could have tagged the |
927a503c BF |
606 | current `mybranch` point by using `git tag <tagname> mybranch`). |
607 | ||
608 | You normally only do signed tags for major releases or things | |
609 | like that, while the light-weight tags are useful for any marking you | |
610 | want to do -- any time you decide that you want to remember a certain | |
611 | point, just create a private tag for it, and you have a nice symbolic | |
612 | name for the state at that point. | |
613 | ||
614 | ||
615 | Copying repositories | |
616 | -------------------- | |
617 | ||
aacd404e | 618 | git repositories are normally totally self-sufficient and relocatable. |
927a503c BF |
619 | Unlike CVS, for example, there is no separate notion of |
620 | "repository" and "working tree". A git repository normally *is* the | |
621 | working tree, with the local git information hidden in the `.git` | |
622 | subdirectory. There is nothing else. What you see is what you got. | |
623 | ||
624 | [NOTE] | |
625 | You can tell git to split the git internal information from | |
626 | the directory that it tracks, but we'll ignore that for now: it's not | |
627 | how normal projects work, and it's really only meant for special uses. | |
628 | So the mental model of "the git information is always tied directly to | |
629 | the working tree that it describes" may not be technically 100% | |
630 | accurate, but it's a good model for all normal use. | |
631 | ||
a6080a0a | 632 | This has two implications: |
927a503c BF |
633 | |
634 | - if you grow bored with the tutorial repository you created (or you've | |
635 | made a mistake and want to start all over), you can just do simple | |
636 | + | |
637 | ---------------- | |
638 | $ rm -rf git-tutorial | |
639 | ---------------- | |
640 | + | |
641 | and it will be gone. There's no external repository, and there's no | |
642 | history outside the project you created. | |
643 | ||
644 | - if you want to move or duplicate a git repository, you can do so. There | |
ba020ef5 | 645 | is 'git-clone' command, but if all you want to do is just to |
927a503c BF |
646 | create a copy of your repository (with all the full history that |
647 | went along with it), you can do so with a regular | |
648 | `cp -a git-tutorial new-git-tutorial`. | |
649 | + | |
650 | Note that when you've moved or copied a git repository, your git index | |
651 | file (which caches various information, notably some of the "stat" | |
652 | information for the files involved) will likely need to be refreshed. | |
653 | So after you do a `cp -a` to create a new copy, you'll want to do | |
654 | + | |
655 | ---------------- | |
b1889c36 | 656 | $ git update-index --refresh |
927a503c BF |
657 | ---------------- |
658 | + | |
659 | in the new repository to make sure that the index file is up-to-date. | |
660 | ||
661 | Note that the second point is true even across machines. You can | |
662 | duplicate a remote git repository with *any* regular copy mechanism, be it | |
2fd02c92 | 663 | 'scp', 'rsync' or 'wget'. |
927a503c BF |
664 | |
665 | When copying a remote repository, you'll want to at a minimum update the | |
666 | index cache when you do this, and especially with other peoples' | |
667 | repositories you often want to make sure that the index cache is in some | |
668 | known state (you don't know *what* they've done and not yet checked in), | |
ba020ef5 | 669 | so usually you'll precede the 'git-update-index' with a |
927a503c BF |
670 | |
671 | ---------------- | |
b1889c36 JN |
672 | $ git read-tree --reset HEAD |
673 | $ git update-index --refresh | |
927a503c BF |
674 | ---------------- |
675 | ||
676 | which will force a total index re-build from the tree pointed to by `HEAD`. | |
ba020ef5 | 677 | It resets the index contents to `HEAD`, and then the 'git-update-index' |
927a503c BF |
678 | makes sure to match up all index entries with the checked-out files. |
679 | If the original repository had uncommitted changes in its | |
b1889c36 | 680 | working tree, `git update-index --refresh` notices them and |
927a503c BF |
681 | tells you they need to be updated. |
682 | ||
683 | The above can also be written as simply | |
684 | ||
685 | ---------------- | |
686 | $ git reset | |
687 | ---------------- | |
688 | ||
689 | and in fact a lot of the common git command combinations can be scripted | |
690 | with the `git xyz` interfaces. You can learn things by just looking | |
3b27428b | 691 | at what the various git scripts do. For example, `git reset` used to be |
ba020ef5 JN |
692 | the above two lines implemented in 'git-reset', but some things like |
693 | 'git-status' and 'git-commit' are slightly more complex scripts around | |
927a503c BF |
694 | the basic git commands. |
695 | ||
696 | Many (most?) public remote repositories will not contain any of | |
697 | the checked out files or even an index file, and will *only* contain the | |
698 | actual core git files. Such a repository usually doesn't even have the | |
699 | `.git` subdirectory, but has all the git files directly in the | |
a6080a0a | 700 | repository. |
927a503c BF |
701 | |
702 | To create your own local live copy of such a "raw" git repository, you'd | |
703 | first create your own subdirectory for the project, and then copy the | |
704 | raw repository contents into the `.git` directory. For example, to | |
705 | create your own copy of the git repository, you'd do the following | |
706 | ||
707 | ---------------- | |
708 | $ mkdir my-git | |
709 | $ cd my-git | |
710 | $ rsync -rL rsync://rsync.kernel.org/pub/scm/git/git.git/ .git | |
711 | ---------------- | |
712 | ||
a6080a0a | 713 | followed by |
927a503c BF |
714 | |
715 | ---------------- | |
b1889c36 | 716 | $ git read-tree HEAD |
927a503c BF |
717 | ---------------- |
718 | ||
719 | to populate the index. However, now you have populated the index, and | |
720 | you have all the git internal files, but you will notice that you don't | |
721 | actually have any of the working tree files to work on. To get | |
722 | those, you'd check them out with | |
723 | ||
724 | ---------------- | |
b1889c36 | 725 | $ git checkout-index -u -a |
927a503c BF |
726 | ---------------- |
727 | ||
728 | where the `-u` flag means that you want the checkout to keep the index | |
729 | up-to-date (so that you don't have to refresh it afterward), and the | |
730 | `-a` flag means "check out all files" (if you have a stale copy or an | |
731 | older version of a checked out tree you may also need to add the `-f` | |
ba020ef5 | 732 | flag first, to tell 'git-checkout-index' to *force* overwriting of any old |
a6080a0a | 733 | files). |
927a503c BF |
734 | |
735 | Again, this can all be simplified with | |
736 | ||
737 | ---------------- | |
738 | $ git clone rsync://rsync.kernel.org/pub/scm/git/git.git/ my-git | |
739 | $ cd my-git | |
740 | $ git checkout | |
741 | ---------------- | |
742 | ||
743 | which will end up doing all of the above for you. | |
744 | ||
745 | You have now successfully copied somebody else's (mine) remote | |
a6080a0a | 746 | repository, and checked it out. |
927a503c BF |
747 | |
748 | ||
749 | Creating a new branch | |
750 | --------------------- | |
751 | ||
752 | Branches in git are really nothing more than pointers into the git | |
753 | object database from within the `.git/refs/` subdirectory, and as we | |
754 | already discussed, the `HEAD` branch is nothing but a symlink to one of | |
a6080a0a | 755 | these object pointers. |
927a503c BF |
756 | |
757 | You can at any time create a new branch by just picking an arbitrary | |
758 | point in the project history, and just writing the SHA1 name of that | |
759 | object into a file under `.git/refs/heads/`. You can use any filename you | |
760 | want (and indeed, subdirectories), but the convention is that the | |
761 | "normal" branch is called `master`. That's just a convention, though, | |
a6080a0a | 762 | and nothing enforces it. |
927a503c BF |
763 | |
764 | To show that as an example, let's go back to the git-tutorial repository we | |
765 | used earlier, and create a branch in it. You do that by simply just | |
766 | saying that you want to check out a new branch: | |
767 | ||
768 | ------------ | |
769 | $ git checkout -b mybranch | |
770 | ------------ | |
771 | ||
772 | will create a new branch based at the current `HEAD` position, and switch | |
a6080a0a | 773 | to it. |
927a503c BF |
774 | |
775 | [NOTE] | |
776 | ================================================ | |
777 | If you make the decision to start your new branch at some | |
778 | other point in the history than the current `HEAD`, you can do so by | |
ba020ef5 | 779 | just telling 'git-checkout' what the base of the checkout would be. |
927a503c BF |
780 | In other words, if you have an earlier tag or branch, you'd just do |
781 | ||
782 | ------------ | |
783 | $ git checkout -b mybranch earlier-commit | |
784 | ------------ | |
785 | ||
786 | and it would create the new branch `mybranch` at the earlier commit, | |
787 | and check out the state at that time. | |
788 | ================================================ | |
789 | ||
790 | You can always just jump back to your original `master` branch by doing | |
791 | ||
792 | ------------ | |
793 | $ git checkout master | |
794 | ------------ | |
795 | ||
796 | (or any other branch-name, for that matter) and if you forget which | |
797 | branch you happen to be on, a simple | |
798 | ||
927a503c BF |
799 | ------------ |
800 | $ cat .git/HEAD | |
801 | ------------ | |
802 | ||
960c7021 JH |
803 | will tell you where it's pointing. To get the list of branches |
804 | you have, you can say | |
927a503c BF |
805 | |
806 | ------------ | |
807 | $ git branch | |
808 | ------------ | |
809 | ||
3b27428b BS |
810 | which used to be nothing more than a simple script around `ls .git/refs/heads`. |
811 | There will be an asterisk in front of the branch you are currently on. | |
927a503c BF |
812 | |
813 | Sometimes you may wish to create a new branch _without_ actually | |
814 | checking it out and switching to it. If so, just use the command | |
815 | ||
816 | ------------ | |
817 | $ git branch <branchname> [startingpoint] | |
818 | ------------ | |
819 | ||
a6080a0a | 820 | which will simply _create_ the branch, but will not do anything further. |
927a503c | 821 | You can then later -- once you decide that you want to actually develop |
ba020ef5 | 822 | on that branch -- switch to that branch with a regular 'git-checkout' |
927a503c BF |
823 | with the branchname as the argument. |
824 | ||
825 | ||
826 | Merging two branches | |
827 | -------------------- | |
828 | ||
829 | One of the ideas of having a branch is that you do some (possibly | |
830 | experimental) work in it, and eventually merge it back to the main | |
831 | branch. So assuming you created the above `mybranch` that started out | |
832 | being the same as the original `master` branch, let's make sure we're in | |
833 | that branch, and do some work there. | |
834 | ||
835 | ------------------------------------------------ | |
836 | $ git checkout mybranch | |
837 | $ echo "Work, work, work" >>hello | |
d336fc09 | 838 | $ git commit -m "Some work." -i hello |
927a503c BF |
839 | ------------------------------------------------ |
840 | ||
841 | Here, we just added another line to `hello`, and we used a shorthand for | |
b1889c36 | 842 | doing both `git update-index hello` and `git commit` by just giving the |
960c7021 JH |
843 | filename directly to `git commit`, with an `-i` flag (it tells |
844 | git to 'include' that file in addition to what you have done to | |
845 | the index file so far when making the commit). The `-m` flag is to give the | |
927a503c BF |
846 | commit log message from the command line. |
847 | ||
848 | Now, to make it a bit more interesting, let's assume that somebody else | |
849 | does some work in the original branch, and simulate that by going back | |
850 | to the master branch, and editing the same file differently there: | |
851 | ||
852 | ------------ | |
853 | $ git checkout master | |
854 | ------------ | |
855 | ||
856 | Here, take a moment to look at the contents of `hello`, and notice how they | |
857 | don't contain the work we just did in `mybranch` -- because that work | |
858 | hasn't happened in the `master` branch at all. Then do | |
859 | ||
860 | ------------ | |
861 | $ echo "Play, play, play" >>hello | |
862 | $ echo "Lots of fun" >>example | |
d336fc09 | 863 | $ git commit -m "Some fun." -i hello example |
927a503c BF |
864 | ------------ |
865 | ||
866 | since the master branch is obviously in a much better mood. | |
867 | ||
868 | Now, you've got two branches, and you decide that you want to merge the | |
869 | work done. Before we do that, let's introduce a cool graphical tool that | |
870 | helps you view what's going on: | |
871 | ||
872 | ---------------- | |
873 | $ gitk --all | |
874 | ---------------- | |
875 | ||
876 | will show you graphically both of your branches (that's what the `\--all` | |
877 | means: normally it will just show you your current `HEAD`) and their | |
878 | histories. You can also see exactly how they came to be from a common | |
a6080a0a | 879 | source. |
927a503c | 880 | |
42d36bb8 | 881 | Anyway, let's exit 'gitk' (`^Q` or the File menu), and decide that we want |
927a503c BF |
882 | to merge the work we did on the `mybranch` branch into the `master` |
883 | branch (which is currently our `HEAD` too). To do that, there's a nice | |
ba020ef5 | 884 | script called 'git-merge', which wants to know which branches you want |
927a503c BF |
885 | to resolve and what the merge is all about: |
886 | ||
887 | ------------ | |
ba17892d | 888 | $ git merge -m "Merge work in mybranch" mybranch |
927a503c BF |
889 | ------------ |
890 | ||
891 | where the first argument is going to be used as the commit message if | |
892 | the merge can be resolved automatically. | |
893 | ||
894 | Now, in this case we've intentionally created a situation where the | |
895 | merge will need to be fixed up by hand, though, so git will do as much | |
896 | of it as it can automatically (which in this case is just merge the `example` | |
897 | file, which had no differences in the `mybranch` branch), and say: | |
898 | ||
899 | ---------------- | |
a6080a0a JH |
900 | Auto-merging hello |
901 | CONFLICT (content): Merge conflict in hello | |
960c7021 | 902 | Automatic merge failed; fix up by hand |
927a503c BF |
903 | ---------------- |
904 | ||
5fe3acc4 JH |
905 | It tells you that it did an "Automatic merge", which |
906 | failed due to conflicts in `hello`. | |
927a503c BF |
907 | |
908 | Not to worry. It left the (trivial) conflict in `hello` in the same form you | |
909 | should already be well used to if you've ever used CVS, so let's just | |
910 | open `hello` in our editor (whatever that may be), and fix it up somehow. | |
911 | I'd suggest just making it so that `hello` contains all four lines: | |
912 | ||
913 | ------------ | |
914 | Hello World | |
915 | It's a new day for git | |
916 | Play, play, play | |
917 | Work, work, work | |
918 | ------------ | |
919 | ||
920 | and once you're happy with your manual merge, just do a | |
921 | ||
922 | ------------ | |
130fcca6 | 923 | $ git commit -i hello |
927a503c BF |
924 | ------------ |
925 | ||
926 | which will very loudly warn you that you're now committing a merge | |
927 | (which is correct, so never mind), and you can write a small merge | |
ba020ef5 | 928 | message about your adventures in 'git-merge'-land. |
927a503c BF |
929 | |
930 | After you're done, start up `gitk \--all` to see graphically what the | |
931 | history looks like. Notice that `mybranch` still exists, and you can | |
932 | switch to it, and continue to work with it if you want to. The | |
933 | `mybranch` branch will not contain the merge, but next time you merge it | |
934 | from the `master` branch, git will know how you merged it, so you'll not | |
935 | have to do _that_ merge again. | |
936 | ||
937 | Another useful tool, especially if you do not always work in X-Window | |
938 | environment, is `git show-branch`. | |
939 | ||
940 | ------------------------------------------------ | |
b1889c36 | 941 | $ git show-branch --topo-order --more=1 master mybranch |
927a503c BF |
942 | * [master] Merge work in mybranch |
943 | ! [mybranch] Some work. | |
944 | -- | |
945 | - [master] Merge work in mybranch | |
946 | *+ [mybranch] Some work. | |
2782c935 | 947 | * [master^] Some fun. |
927a503c BF |
948 | ------------------------------------------------ |
949 | ||
950 | The first two lines indicate that it is showing the two branches | |
951 | and the first line of the commit log message from their | |
952 | top-of-the-tree commits, you are currently on `master` branch | |
245f1029 | 953 | (notice the asterisk `\*` character), and the first column for |
927a503c BF |
954 | the later output lines is used to show commits contained in the |
955 | `master` branch, and the second column for the `mybranch` | |
956 | branch. Three commits are shown along with their log messages. | |
957 | All of them have non blank characters in the first column (`*` | |
3b27428b | 958 | shows an ordinary commit on the current branch, `-` is a merge commit), which |
927a503c BF |
959 | means they are now part of the `master` branch. Only the "Some |
960 | work" commit has the plus `+` character in the second column, | |
961 | because `mybranch` has not been merged to incorporate these | |
962 | commits from the master branch. The string inside brackets | |
963 | before the commit log message is a short name you can use to | |
964 | name the commit. In the above example, 'master' and 'mybranch' | |
2782c935 | 965 | are branch heads. 'master^' is the first parent of 'master' |
483bc4f0 | 966 | branch head. Please see linkgit:git-rev-parse[1] if you want to |
927a503c BF |
967 | see more complex cases. |
968 | ||
2782c935 | 969 | [NOTE] |
ba020ef5 | 970 | Without the '--more=1' option, 'git-show-branch' would not output the |
2782c935 | 971 | '[master^]' commit, as '[mybranch]' commit is a common ancestor of |
483bc4f0 JN |
972 | both 'master' and 'mybranch' tips. Please see linkgit:git-show-branch[1] |
973 | for details. | |
2782c935 SO |
974 | |
975 | [NOTE] | |
976 | If there were more commits on the 'master' branch after the merge, the | |
ba020ef5 | 977 | merge commit itself would not be shown by 'git-show-branch' by |
2782c935 SO |
978 | default. You would need to provide '--sparse' option to make the |
979 | merge commit visible in this case. | |
980 | ||
927a503c BF |
981 | Now, let's pretend you are the one who did all the work in |
982 | `mybranch`, and the fruit of your hard work has finally been merged | |
983 | to the `master` branch. Let's go back to `mybranch`, and run | |
ba020ef5 | 984 | 'git-merge' to get the "upstream changes" back to your branch. |
927a503c BF |
985 | |
986 | ------------ | |
987 | $ git checkout mybranch | |
ba17892d | 988 | $ git merge -m "Merge upstream changes." master |
927a503c BF |
989 | ------------ |
990 | ||
991 | This outputs something like this (the actual commit object names | |
992 | would be different) | |
993 | ||
994 | ---------------- | |
995 | Updating from ae3a2da... to a80b4aa.... | |
960c7021 | 996 | Fast forward |
927a503c BF |
997 | example | 1 + |
998 | hello | 1 + | |
999 | 2 files changed, 2 insertions(+), 0 deletions(-) | |
1000 | ---------------- | |
1001 | ||
1002 | Because your branch did not contain anything more than what are | |
207dfa07 | 1003 | already merged into the `master` branch, the merge operation did |
927a503c BF |
1004 | not actually do a merge. Instead, it just updated the top of |
1005 | the tree of your branch to that of the `master` branch. This is | |
1006 | often called 'fast forward' merge. | |
1007 | ||
1008 | You can run `gitk \--all` again to see how the commit ancestry | |
5833d730 | 1009 | looks like, or run 'show-branch', which tells you this. |
927a503c BF |
1010 | |
1011 | ------------------------------------------------ | |
1012 | $ git show-branch master mybranch | |
1013 | ! [master] Merge work in mybranch | |
1014 | * [mybranch] Merge work in mybranch | |
1015 | -- | |
1016 | -- [master] Merge work in mybranch | |
1017 | ------------------------------------------------ | |
1018 | ||
1019 | ||
1020 | Merging external work | |
1021 | --------------------- | |
1022 | ||
1023 | It's usually much more common that you merge with somebody else than | |
1024 | merging with your own branches, so it's worth pointing out that git | |
1025 | makes that very easy too, and in fact, it's not that different from | |
ba020ef5 | 1026 | doing a 'git-merge'. In fact, a remote merge ends up being nothing |
927a503c | 1027 | more than "fetch the work from a remote repository into a temporary tag" |
ba020ef5 | 1028 | followed by a 'git-merge'. |
927a503c BF |
1029 | |
1030 | Fetching from a remote repository is done by, unsurprisingly, | |
ba020ef5 | 1031 | 'git-fetch': |
927a503c BF |
1032 | |
1033 | ---------------- | |
1034 | $ git fetch <remote-repository> | |
1035 | ---------------- | |
1036 | ||
1037 | One of the following transports can be used to name the | |
1038 | repository to download from: | |
1039 | ||
1040 | Rsync:: | |
1041 | `rsync://remote.machine/path/to/repo.git/` | |
1042 | + | |
1043 | Rsync transport is usable for both uploading and downloading, | |
1044 | but is completely unaware of what git does, and can produce | |
1045 | unexpected results when you download from the public repository | |
1046 | while the repository owner is uploading into it via `rsync` | |
1047 | transport. Most notably, it could update the files under | |
1048 | `refs/` which holds the object name of the topmost commits | |
1049 | before uploading the files in `objects/` -- the downloader would | |
1050 | obtain head commit object name while that object itself is still | |
1051 | not available in the repository. For this reason, it is | |
1052 | considered deprecated. | |
1053 | ||
1054 | SSH:: | |
1055 | `remote.machine:/path/to/repo.git/` or | |
1056 | + | |
1057 | `ssh://remote.machine/path/to/repo.git/` | |
1058 | + | |
1059 | This transport can be used for both uploading and downloading, | |
1060 | and requires you to have a log-in privilege over `ssh` to the | |
1061 | remote machine. It finds out the set of objects the other side | |
1062 | lacks by exchanging the head commits both ends have and | |
1063 | transfers (close to) minimum set of objects. It is by far the | |
1064 | most efficient way to exchange git objects between repositories. | |
1065 | ||
1066 | Local directory:: | |
1067 | `/path/to/repo.git/` | |
1068 | + | |
2fd02c92 | 1069 | This transport is the same as SSH transport but uses 'sh' to run |
927a503c | 1070 | both ends on the local machine instead of running other end on |
2fd02c92 | 1071 | the remote machine via 'ssh'. |
927a503c BF |
1072 | |
1073 | git Native:: | |
1074 | `git://remote.machine/path/to/repo.git/` | |
1075 | + | |
1076 | This transport was designed for anonymous downloading. Like SSH | |
1077 | transport, it finds out the set of objects the downstream side | |
1078 | lacks and transfers (close to) minimum set of objects. | |
1079 | ||
1080 | HTTP(S):: | |
1081 | `http://remote.machine/path/to/repo.git/` | |
1082 | + | |
1083 | Downloader from http and https URL | |
1084 | first obtains the topmost commit object name from the remote site | |
1085 | by looking at the specified refname under `repo.git/refs/` directory, | |
1086 | and then tries to obtain the | |
1087 | commit object by downloading from `repo.git/objects/xx/xxx\...` | |
1088 | using the object name of that commit object. Then it reads the | |
1089 | commit object to find out its parent commits and the associate | |
1090 | tree object; it repeats this process until it gets all the | |
abda1ef5 | 1091 | necessary objects. Because of this behavior, they are |
927a503c BF |
1092 | sometimes also called 'commit walkers'. |
1093 | + | |
1094 | The 'commit walkers' are sometimes also called 'dumb | |
1095 | transports', because they do not require any git aware smart | |
1096 | server like git Native transport does. Any stock HTTP server | |
1097 | that does not even support directory index would suffice. But | |
ba020ef5 | 1098 | you must prepare your repository with 'git-update-server-info' |
927a503c | 1099 | to help dumb transport downloaders. |
927a503c | 1100 | |
207dfa07 | 1101 | Once you fetch from the remote repository, you `merge` that |
927a503c BF |
1102 | with your current branch. |
1103 | ||
1104 | However -- it's such a common thing to `fetch` and then | |
207dfa07 | 1105 | immediately `merge`, that it's called `git pull`, and you can |
927a503c BF |
1106 | simply do |
1107 | ||
1108 | ---------------- | |
1109 | $ git pull <remote-repository> | |
1110 | ---------------- | |
1111 | ||
1112 | and optionally give a branch-name for the remote end as a second | |
1113 | argument. | |
1114 | ||
1115 | [NOTE] | |
1116 | You could do without using any branches at all, by | |
1117 | keeping as many local repositories as you would like to have | |
ba020ef5 | 1118 | branches, and merging between them with 'git-pull', just like |
927a503c | 1119 | you merge between branches. The advantage of this approach is |
aacd404e | 1120 | that it lets you keep a set of files for each `branch` checked |
927a503c BF |
1121 | out and you may find it easier to switch back and forth if you |
1122 | juggle multiple lines of development simultaneously. Of | |
1123 | course, you will pay the price of more disk usage to hold | |
1124 | multiple working trees, but disk space is cheap these days. | |
1125 | ||
927a503c BF |
1126 | It is likely that you will be pulling from the same remote |
1127 | repository from time to time. As a short hand, you can store | |
c14261ea NP |
1128 | the remote repository URL in the local repository's config file |
1129 | like this: | |
927a503c BF |
1130 | |
1131 | ------------------------------------------------ | |
e0d10e1c | 1132 | $ git config remote.linus.url http://www.kernel.org/pub/scm/git/git.git/ |
927a503c BF |
1133 | ------------------------------------------------ |
1134 | ||
ba020ef5 | 1135 | and use the "linus" keyword with 'git-pull' instead of the full URL. |
927a503c BF |
1136 | |
1137 | Examples. | |
1138 | ||
1139 | . `git pull linus` | |
1140 | . `git pull linus tag v0.99.1` | |
927a503c BF |
1141 | |
1142 | the above are equivalent to: | |
1143 | ||
1144 | . `git pull http://www.kernel.org/pub/scm/git/git.git/ HEAD` | |
1145 | . `git pull http://www.kernel.org/pub/scm/git/git.git/ tag v0.99.1` | |
927a503c BF |
1146 | |
1147 | ||
1148 | How does the merge work? | |
1149 | ------------------------ | |
1150 | ||
1151 | We said this tutorial shows what plumbing does to help you cope | |
1152 | with the porcelain that isn't flushing, but we so far did not | |
1153 | talk about how the merge really works. If you are following | |
1154 | this tutorial the first time, I'd suggest to skip to "Publishing | |
1155 | your work" section and come back here later. | |
1156 | ||
1157 | OK, still with me? To give us an example to look at, let's go | |
1158 | back to the earlier repository with "hello" and "example" file, | |
1159 | and bring ourselves back to the pre-merge state: | |
1160 | ||
1161 | ------------ | |
065c5ac1 | 1162 | $ git show-branch --more=2 master mybranch |
927a503c BF |
1163 | ! [master] Merge work in mybranch |
1164 | * [mybranch] Merge work in mybranch | |
1165 | -- | |
1166 | -- [master] Merge work in mybranch | |
1167 | +* [master^2] Some work. | |
1168 | +* [master^] Some fun. | |
1169 | ------------ | |
1170 | ||
ba020ef5 | 1171 | Remember, before running 'git-merge', our `master` head was at |
927a503c BF |
1172 | "Some fun." commit, while our `mybranch` head was at "Some |
1173 | work." commit. | |
1174 | ||
1175 | ------------ | |
1176 | $ git checkout mybranch | |
1177 | $ git reset --hard master^2 | |
1178 | $ git checkout master | |
1179 | $ git reset --hard master^ | |
1180 | ------------ | |
1181 | ||
1182 | After rewinding, the commit structure should look like this: | |
1183 | ||
1184 | ------------ | |
1185 | $ git show-branch | |
1186 | * [master] Some fun. | |
1187 | ! [mybranch] Some work. | |
1188 | -- | |
1189 | + [mybranch] Some work. | |
1190 | * [master] Some fun. | |
1191 | *+ [mybranch^] New day. | |
1192 | ------------ | |
1193 | ||
1194 | Now we are ready to experiment with the merge by hand. | |
1195 | ||
1196 | `git merge` command, when merging two branches, uses 3-way merge | |
1197 | algorithm. First, it finds the common ancestor between them. | |
ba020ef5 | 1198 | The command it uses is 'git-merge-base': |
927a503c BF |
1199 | |
1200 | ------------ | |
b1889c36 | 1201 | $ mb=$(git merge-base HEAD mybranch) |
927a503c BF |
1202 | ------------ |
1203 | ||
1204 | The command writes the commit object name of the common ancestor | |
1205 | to the standard output, so we captured its output to a variable, | |
3b27428b | 1206 | because we will be using it in the next step. By the way, the common |
927a503c BF |
1207 | ancestor commit is the "New day." commit in this case. You can |
1208 | tell it by: | |
1209 | ||
1210 | ------------ | |
b1889c36 | 1211 | $ git name-rev $mb |
927a503c BF |
1212 | my-first-tag |
1213 | ------------ | |
1214 | ||
1215 | After finding out a common ancestor commit, the second step is | |
1216 | this: | |
1217 | ||
1218 | ------------ | |
b1889c36 | 1219 | $ git read-tree -m -u $mb HEAD mybranch |
927a503c BF |
1220 | ------------ |
1221 | ||
ba020ef5 | 1222 | This is the same 'git-read-tree' command we have already seen, |
927a503c BF |
1223 | but it takes three trees, unlike previous examples. This reads |
1224 | the contents of each tree into different 'stage' in the index | |
065c5ac1 | 1225 | file (the first tree goes to stage 1, the second to stage 2, |
927a503c BF |
1226 | etc.). After reading three trees into three stages, the paths |
1227 | that are the same in all three stages are 'collapsed' into stage | |
1228 | 0. Also paths that are the same in two of three stages are | |
1229 | collapsed into stage 0, taking the SHA1 from either stage 2 or | |
1230 | stage 3, whichever is different from stage 1 (i.e. only one side | |
1231 | changed from the common ancestor). | |
1232 | ||
1233 | After 'collapsing' operation, paths that are different in three | |
1234 | trees are left in non-zero stages. At this point, you can | |
1235 | inspect the index file with this command: | |
1236 | ||
1237 | ------------ | |
b1889c36 | 1238 | $ git ls-files --stage |
927a503c BF |
1239 | 100644 7f8b141b65fdcee47321e399a2598a235a032422 0 example |
1240 | 100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello | |
1241 | 100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello | |
1242 | 100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello | |
1243 | ------------ | |
1244 | ||
1245 | In our example of only two files, we did not have unchanged | |
1246 | files so only 'example' resulted in collapsing, but in real-life | |
1247 | large projects, only small number of files change in one commit, | |
1248 | and this 'collapsing' tends to trivially merge most of the paths | |
1249 | fairly quickly, leaving only a handful the real changes in non-zero | |
1250 | stages. | |
1251 | ||
1252 | To look at only non-zero stages, use `\--unmerged` flag: | |
1253 | ||
1254 | ------------ | |
b1889c36 | 1255 | $ git ls-files --unmerged |
927a503c BF |
1256 | 100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello |
1257 | 100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello | |
1258 | 100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello | |
1259 | ------------ | |
1260 | ||
1261 | The next step of merging is to merge these three versions of the | |
1262 | file, using 3-way merge. This is done by giving | |
ba020ef5 JN |
1263 | 'git-merge-one-file' command as one of the arguments to |
1264 | 'git-merge-index' command: | |
927a503c BF |
1265 | |
1266 | ------------ | |
b1889c36 | 1267 | $ git merge-index git-merge-one-file hello |
927a503c BF |
1268 | Auto-merging hello. |
1269 | merge: warning: conflicts during merge | |
1270 | ERROR: Merge conflict in hello. | |
1271 | fatal: merge program failed | |
1272 | ------------ | |
1273 | ||
ba020ef5 | 1274 | 'git-merge-one-file' script is called with parameters to |
927a503c BF |
1275 | describe those three versions, and is responsible to leave the |
1276 | merge results in the working tree. | |
1277 | It is a fairly straightforward shell script, and | |
2fd02c92 JN |
1278 | eventually calls 'merge' program from RCS suite to perform a |
1279 | file-level 3-way merge. In this case, 'merge' detects | |
927a503c BF |
1280 | conflicts, and the merge result with conflict marks is left in |
1281 | the working tree.. This can be seen if you run `ls-files | |
1282 | --stage` again at this point: | |
1283 | ||
1284 | ------------ | |
b1889c36 | 1285 | $ git ls-files --stage |
927a503c BF |
1286 | 100644 7f8b141b65fdcee47321e399a2598a235a032422 0 example |
1287 | 100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello | |
1288 | 100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello | |
1289 | 100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello | |
1290 | ------------ | |
1291 | ||
1292 | This is the state of the index file and the working file after | |
ba020ef5 | 1293 | 'git-merge' returns control back to you, leaving the conflicting |
927a503c | 1294 | merge for you to resolve. Notice that the path `hello` is still |
ba020ef5 | 1295 | unmerged, and what you see with 'git-diff' at this point is |
927a503c BF |
1296 | differences since stage 2 (i.e. your version). |
1297 | ||
1298 | ||
1299 | Publishing your work | |
1300 | -------------------- | |
1301 | ||
aacd404e | 1302 | So, we can use somebody else's work from a remote repository, but |
927a503c BF |
1303 | how can *you* prepare a repository to let other people pull from |
1304 | it? | |
1305 | ||
79dbbedd | 1306 | You do your real work in your working tree that has your |
927a503c BF |
1307 | primary repository hanging under it as its `.git` subdirectory. |
1308 | You *could* make that repository accessible remotely and ask | |
1309 | people to pull from it, but in practice that is not the way | |
1310 | things are usually done. A recommended way is to have a public | |
1311 | repository, make it reachable by other people, and when the | |
1312 | changes you made in your primary working tree are in good shape, | |
1313 | update the public repository from it. This is often called | |
1314 | 'pushing'. | |
1315 | ||
1316 | [NOTE] | |
1317 | This public repository could further be mirrored, and that is | |
1318 | how git repositories at `kernel.org` are managed. | |
1319 | ||
1320 | Publishing the changes from your local (private) repository to | |
1321 | your remote (public) repository requires a write privilege on | |
1322 | the remote machine. You need to have an SSH account there to | |
ba020ef5 | 1323 | run a single command, 'git-receive-pack'. |
927a503c BF |
1324 | |
1325 | First, you need to create an empty repository on the remote | |
1326 | machine that will house your public repository. This empty | |
1327 | repository will be populated and be kept up-to-date by pushing | |
1328 | into it later. Obviously, this repository creation needs to be | |
1329 | done only once. | |
1330 | ||
1331 | [NOTE] | |
ba020ef5 JN |
1332 | 'git-push' uses a pair of programs, |
1333 | 'git-send-pack' on your local machine, and 'git-receive-pack' | |
927a503c BF |
1334 | on the remote machine. The communication between the two over |
1335 | the network internally uses an SSH connection. | |
1336 | ||
1337 | Your private repository's git directory is usually `.git`, but | |
1338 | your public repository is often named after the project name, | |
1339 | i.e. `<project>.git`. Let's create such a public repository for | |
1340 | project `my-git`. After logging into the remote machine, create | |
1341 | an empty directory: | |
1342 | ||
1343 | ------------ | |
1344 | $ mkdir my-git.git | |
1345 | ------------ | |
1346 | ||
1347 | Then, make that directory into a git repository by running | |
ba020ef5 | 1348 | 'git-init', but this time, since its name is not the usual |
927a503c BF |
1349 | `.git`, we do things slightly differently: |
1350 | ||
1351 | ------------ | |
b1889c36 | 1352 | $ GIT_DIR=my-git.git git init |
927a503c BF |
1353 | ------------ |
1354 | ||
1355 | Make sure this directory is available for others you want your | |
1356 | changes to be pulled by via the transport of your choice. Also | |
ba020ef5 | 1357 | you need to make sure that you have the 'git-receive-pack' |
927a503c BF |
1358 | program on the `$PATH`. |
1359 | ||
1360 | [NOTE] | |
1361 | Many installations of sshd do not invoke your shell as the login | |
1362 | shell when you directly run programs; what this means is that if | |
2fd02c92 | 1363 | your login shell is 'bash', only `.bashrc` is read and not |
927a503c | 1364 | `.bash_profile`. As a workaround, make sure `.bashrc` sets up |
ba020ef5 | 1365 | `$PATH` so that you can run 'git-receive-pack' program. |
927a503c BF |
1366 | |
1367 | [NOTE] | |
1368 | If you plan to publish this repository to be accessed over http, | |
7dce9918 PB |
1369 | you should do `mv my-git.git/hooks/post-update.sample |
1370 | my-git.git/hooks/post-update` at this point. | |
1371 | This makes sure that every time you push into this | |
b1889c36 | 1372 | repository, `git update-server-info` is run. |
927a503c BF |
1373 | |
1374 | Your "public repository" is now ready to accept your changes. | |
1375 | Come back to the machine you have your private repository. From | |
1376 | there, run this command: | |
1377 | ||
1378 | ------------ | |
1379 | $ git push <public-host>:/path/to/my-git.git master | |
1380 | ------------ | |
1381 | ||
1382 | This synchronizes your public repository to match the named | |
1383 | branch head (i.e. `master` in this case) and objects reachable | |
1384 | from them in your current repository. | |
1385 | ||
1386 | As a real example, this is how I update my public git | |
1387 | repository. Kernel.org mirror network takes care of the | |
1388 | propagation to other publicly visible machines: | |
1389 | ||
1390 | ------------ | |
a6080a0a | 1391 | $ git push master.kernel.org:/pub/scm/git/git.git/ |
927a503c BF |
1392 | ------------ |
1393 | ||
1394 | ||
1395 | Packing your repository | |
1396 | ----------------------- | |
1397 | ||
1398 | Earlier, we saw that one file under `.git/objects/??/` directory | |
1399 | is stored for each git object you create. This representation | |
1400 | is efficient to create atomically and safely, but | |
1401 | not so convenient to transport over the network. Since git objects are | |
1402 | immutable once they are created, there is a way to optimize the | |
1403 | storage by "packing them together". The command | |
1404 | ||
1405 | ------------ | |
1406 | $ git repack | |
1407 | ------------ | |
1408 | ||
1409 | will do it for you. If you followed the tutorial examples, you | |
1410 | would have accumulated about 17 objects in `.git/objects/??/` | |
ba020ef5 | 1411 | directories by now. 'git-repack' tells you how many objects it |
927a503c BF |
1412 | packed, and stores the packed file in `.git/objects/pack` |
1413 | directory. | |
1414 | ||
1415 | [NOTE] | |
1416 | You will see two files, `pack-\*.pack` and `pack-\*.idx`, | |
1417 | in `.git/objects/pack` directory. They are closely related to | |
1418 | each other, and if you ever copy them by hand to a different | |
1419 | repository for whatever reason, you should make sure you copy | |
1420 | them together. The former holds all the data from the objects | |
1421 | in the pack, and the latter holds the index for random | |
1422 | access. | |
1423 | ||
ba020ef5 | 1424 | If you are paranoid, running 'git-verify-pack' command would |
927a503c BF |
1425 | detect if you have a corrupt pack, but do not worry too much. |
1426 | Our programs are always perfect ;-). | |
1427 | ||
1428 | Once you have packed objects, you do not need to leave the | |
1429 | unpacked objects that are contained in the pack file anymore. | |
1430 | ||
1431 | ------------ | |
1432 | $ git prune-packed | |
1433 | ------------ | |
1434 | ||
1435 | would remove them for you. | |
1436 | ||
1437 | You can try running `find .git/objects -type f` before and after | |
1438 | you run `git prune-packed` if you are curious. Also `git | |
1439 | count-objects` would tell you how many unpacked objects are in | |
1440 | your repository and how much space they are consuming. | |
1441 | ||
1442 | [NOTE] | |
1443 | `git pull` is slightly cumbersome for HTTP transport, as a | |
1444 | packed repository may contain relatively few objects in a | |
1445 | relatively large pack. If you expect many HTTP pulls from your | |
1446 | public repository you might want to repack & prune often, or | |
1447 | never. | |
1448 | ||
1449 | If you run `git repack` again at this point, it will say | |
1450 | "Nothing to pack". Once you continue your development and | |
1451 | accumulate the changes, running `git repack` again will create a | |
1452 | new pack, that contains objects created since you packed your | |
1453 | repository the last time. We recommend that you pack your project | |
1454 | soon after the initial import (unless you are starting your | |
1455 | project from scratch), and then run `git repack` every once in a | |
1456 | while, depending on how active your project is. | |
1457 | ||
1458 | When a repository is synchronized via `git push` and `git pull` | |
1459 | objects packed in the source repository are usually stored | |
1460 | unpacked in the destination, unless rsync transport is used. | |
1461 | While this allows you to use different packing strategies on | |
1462 | both ends, it also means you may need to repack both | |
1463 | repositories every once in a while. | |
1464 | ||
1465 | ||
1466 | Working with Others | |
1467 | ------------------- | |
1468 | ||
1469 | Although git is a truly distributed system, it is often | |
1470 | convenient to organize your project with an informal hierarchy | |
1471 | of developers. Linux kernel development is run this way. There | |
505739f6 | 1472 | is a nice illustration (page 17, "Merges to Mainline") in |
3b27428b | 1473 | link:http://www.xenotime.net/linux/mentor/linux-mentoring-2006.pdf[Randy Dunlap's presentation]. |
927a503c BF |
1474 | |
1475 | It should be stressed that this hierarchy is purely *informal*. | |
1476 | There is nothing fundamental in git that enforces the "chain of | |
1477 | patch flow" this hierarchy implies. You do not have to pull | |
1478 | from only one remote repository. | |
1479 | ||
1480 | A recommended workflow for a "project lead" goes like this: | |
1481 | ||
1482 | 1. Prepare your primary repository on your local machine. Your | |
1483 | work is done there. | |
1484 | ||
1485 | 2. Prepare a public repository accessible to others. | |
1486 | + | |
1487 | If other people are pulling from your repository over dumb | |
1488 | transport protocols (HTTP), you need to keep this repository | |
5c94f87e | 1489 | 'dumb transport friendly'. After `git init`, |
7dce9918 PB |
1490 | `$GIT_DIR/hooks/post-update.sample` copied from the standard templates |
1491 | would contain a call to 'git-update-server-info' | |
1492 | but you need to manually enable the hook with | |
1493 | `mv post-update.sample post-update`. This makes sure | |
1494 | 'git-update-server-info' keeps the necessary files up-to-date. | |
927a503c BF |
1495 | |
1496 | 3. Push into the public repository from your primary | |
1497 | repository. | |
1498 | ||
ba020ef5 | 1499 | 4. 'git-repack' the public repository. This establishes a big |
927a503c | 1500 | pack that contains the initial set of objects as the |
ba020ef5 | 1501 | baseline, and possibly 'git-prune' if the transport |
927a503c BF |
1502 | used for pulling from your repository supports packed |
1503 | repositories. | |
1504 | ||
1505 | 5. Keep working in your primary repository. Your changes | |
1506 | include modifications of your own, patches you receive via | |
1507 | e-mails, and merges resulting from pulling the "public" | |
1508 | repositories of your "subsystem maintainers". | |
1509 | + | |
1510 | You can repack this private repository whenever you feel like. | |
1511 | ||
1512 | 6. Push your changes to the public repository, and announce it | |
1513 | to the public. | |
1514 | ||
b1889c36 | 1515 | 7. Every once in a while, "git-repack" the public repository. |
927a503c BF |
1516 | Go back to step 5. and continue working. |
1517 | ||
1518 | ||
1519 | A recommended work cycle for a "subsystem maintainer" who works | |
1520 | on that project and has an own "public repository" goes like this: | |
1521 | ||
ba020ef5 | 1522 | 1. Prepare your work repository, by 'git-clone' the public |
927a503c | 1523 | repository of the "project lead". The URL used for the |
c14261ea NP |
1524 | initial cloning is stored in the remote.origin.url |
1525 | configuration variable. | |
927a503c BF |
1526 | |
1527 | 2. Prepare a public repository accessible to others, just like | |
1528 | the "project lead" person does. | |
1529 | ||
1530 | 3. Copy over the packed files from "project lead" public | |
1531 | repository to your public repository, unless the "project | |
1532 | lead" repository lives on the same machine as yours. In the | |
1533 | latter case, you can use `objects/info/alternates` file to | |
1534 | point at the repository you are borrowing from. | |
1535 | ||
1536 | 4. Push into the public repository from your primary | |
ba020ef5 | 1537 | repository. Run 'git-repack', and possibly 'git-prune' if the |
927a503c BF |
1538 | transport used for pulling from your repository supports |
1539 | packed repositories. | |
1540 | ||
1541 | 5. Keep working in your primary repository. Your changes | |
1542 | include modifications of your own, patches you receive via | |
1543 | e-mails, and merges resulting from pulling the "public" | |
1544 | repositories of your "project lead" and possibly your | |
1545 | "sub-subsystem maintainers". | |
1546 | + | |
1547 | You can repack this private repository whenever you feel | |
1548 | like. | |
1549 | ||
1550 | 6. Push your changes to your public repository, and ask your | |
1551 | "project lead" and possibly your "sub-subsystem | |
1552 | maintainers" to pull from it. | |
1553 | ||
ba020ef5 | 1554 | 7. Every once in a while, 'git-repack' the public repository. |
927a503c BF |
1555 | Go back to step 5. and continue working. |
1556 | ||
1557 | ||
1558 | A recommended work cycle for an "individual developer" who does | |
1559 | not have a "public" repository is somewhat different. It goes | |
1560 | like this: | |
1561 | ||
ba020ef5 | 1562 | 1. Prepare your work repository, by 'git-clone' the public |
927a503c BF |
1563 | repository of the "project lead" (or a "subsystem |
1564 | maintainer", if you work on a subsystem). The URL used for | |
c14261ea NP |
1565 | the initial cloning is stored in the remote.origin.url |
1566 | configuration variable. | |
927a503c BF |
1567 | |
1568 | 2. Do your work in your repository on 'master' branch. | |
1569 | ||
1570 | 3. Run `git fetch origin` from the public repository of your | |
1571 | upstream every once in a while. This does only the first | |
1572 | half of `git pull` but does not merge. The head of the | |
c14261ea | 1573 | public repository is stored in `.git/refs/remotes/origin/master`. |
927a503c BF |
1574 | |
1575 | 4. Use `git cherry origin` to see which ones of your patches | |
1576 | were accepted, and/or use `git rebase origin` to port your | |
1577 | unmerged changes forward to the updated upstream. | |
1578 | ||
1579 | 5. Use `git format-patch origin` to prepare patches for e-mail | |
1580 | submission to your upstream and send it out. Go back to | |
1581 | step 2. and continue. | |
1582 | ||
1583 | ||
1584 | Working with Others, Shared Repository Style | |
1585 | -------------------------------------------- | |
1586 | ||
1587 | If you are coming from CVS background, the style of cooperation | |
1588 | suggested in the previous section may be new to you. You do not | |
1589 | have to worry. git supports "shared public repository" style of | |
1590 | cooperation you are probably more familiar with as well. | |
1591 | ||
6998e4db | 1592 | See linkgit:gitcvs-migration[7] for the details. |
927a503c BF |
1593 | |
1594 | Bundling your work together | |
1595 | --------------------------- | |
1596 | ||
1597 | It is likely that you will be working on more than one thing at | |
1598 | a time. It is easy to manage those more-or-less independent tasks | |
1599 | using branches with git. | |
1600 | ||
1601 | We have already seen how branches work previously, | |
1602 | with "fun and work" example using two branches. The idea is the | |
1603 | same if there are more than two branches. Let's say you started | |
1604 | out from "master" head, and have some new code in the "master" | |
1605 | branch, and two independent fixes in the "commit-fix" and | |
1606 | "diff-fix" branches: | |
1607 | ||
1608 | ------------ | |
1609 | $ git show-branch | |
1610 | ! [commit-fix] Fix commit message normalization. | |
1611 | ! [diff-fix] Fix rename detection. | |
1612 | * [master] Release candidate #1 | |
1613 | --- | |
1614 | + [diff-fix] Fix rename detection. | |
1615 | + [diff-fix~1] Better common substring algorithm. | |
1616 | + [commit-fix] Fix commit message normalization. | |
1617 | * [master] Release candidate #1 | |
1618 | ++* [diff-fix~2] Pretty-print messages. | |
1619 | ------------ | |
1620 | ||
1621 | Both fixes are tested well, and at this point, you want to merge | |
1622 | in both of them. You could merge in 'diff-fix' first and then | |
1623 | 'commit-fix' next, like this: | |
1624 | ||
1625 | ------------ | |
d336fc09 SO |
1626 | $ git merge -m "Merge fix in diff-fix" diff-fix |
1627 | $ git merge -m "Merge fix in commit-fix" commit-fix | |
927a503c BF |
1628 | ------------ |
1629 | ||
1630 | Which would result in: | |
1631 | ||
1632 | ------------ | |
1633 | $ git show-branch | |
1634 | ! [commit-fix] Fix commit message normalization. | |
1635 | ! [diff-fix] Fix rename detection. | |
1636 | * [master] Merge fix in commit-fix | |
1637 | --- | |
1638 | - [master] Merge fix in commit-fix | |
1639 | + * [commit-fix] Fix commit message normalization. | |
1640 | - [master~1] Merge fix in diff-fix | |
1641 | +* [diff-fix] Fix rename detection. | |
1642 | +* [diff-fix~1] Better common substring algorithm. | |
1643 | * [master~2] Release candidate #1 | |
1644 | ++* [master~3] Pretty-print messages. | |
1645 | ------------ | |
1646 | ||
1647 | However, there is no particular reason to merge in one branch | |
1648 | first and the other next, when what you have are a set of truly | |
1649 | independent changes (if the order mattered, then they are not | |
1650 | independent by definition). You could instead merge those two | |
1651 | branches into the current branch at once. First let's undo what | |
1652 | we just did and start over. We would want to get the master | |
1653 | branch before these two merges by resetting it to 'master~2': | |
1654 | ||
1655 | ------------ | |
1656 | $ git reset --hard master~2 | |
1657 | ------------ | |
1658 | ||
db5d6666 | 1659 | You can make sure `git show-branch` matches the state before |
467c0197 JN |
1660 | those two 'git-merge' you just did. Then, instead of running |
1661 | two 'git-merge' commands in a row, you would merge these two | |
927a503c BF |
1662 | branch heads (this is known as 'making an Octopus'): |
1663 | ||
1664 | ------------ | |
c14261ea | 1665 | $ git merge commit-fix diff-fix |
927a503c BF |
1666 | $ git show-branch |
1667 | ! [commit-fix] Fix commit message normalization. | |
1668 | ! [diff-fix] Fix rename detection. | |
1669 | * [master] Octopus merge of branches 'diff-fix' and 'commit-fix' | |
1670 | --- | |
1671 | - [master] Octopus merge of branches 'diff-fix' and 'commit-fix' | |
1672 | + * [commit-fix] Fix commit message normalization. | |
1673 | +* [diff-fix] Fix rename detection. | |
1674 | +* [diff-fix~1] Better common substring algorithm. | |
1675 | * [master~1] Release candidate #1 | |
1676 | ++* [master~2] Pretty-print messages. | |
1677 | ------------ | |
1678 | ||
1679 | Note that you should not do Octopus because you can. An octopus | |
1680 | is a valid thing to do and often makes it easier to view the | |
c14261ea | 1681 | commit history if you are merging more than two independent |
927a503c BF |
1682 | changes at the same time. However, if you have merge conflicts |
1683 | with any of the branches you are merging in and need to hand | |
1684 | resolve, that is an indication that the development happened in | |
1685 | those branches were not independent after all, and you should | |
1686 | merge two at a time, documenting how you resolved the conflicts, | |
1687 | and the reason why you preferred changes made in one side over | |
1688 | the other. Otherwise it would make the project history harder | |
1689 | to follow, not easier. | |
497c8331 CC |
1690 | |
1691 | SEE ALSO | |
1692 | -------- | |
1693 | linkgit:gittutorial[7], linkgit:gittutorial-2[7], | |
ea449615 | 1694 | linkgit:everyday[7], linkgit:gitcvs-migration[7], |
497c8331 CC |
1695 | link:user-manual.html[The Git User's Manual] |
1696 | ||
1697 | GIT | |
1698 | --- | |
9e1f0a85 | 1699 | Part of the linkgit:git[1] suite. |