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1 | A git core tutorial for developers |
2 | ================================== | |
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3 | |
4 | Introduction | |
5 | ------------ | |
6 | ||
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7 | This tutorial explains how to use the "core" git programs to set up and |
8 | work with a git repository. | |
927a503c | 9 | |
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10 | If you just need to use git as a revision control system you may prefer |
11 | to start with link:tutorial.html[a tutorial introduction to git] or | |
12 | link:user-manual.html[the git user manual]. | |
13 | ||
14 | However, an understanding of these low-level tools can be helpful if | |
15 | you want to understand git's internals. | |
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16 | |
17 | The core git is often called "plumbing", with the prettier user | |
18 | interfaces on top of it called "porcelain". You may not want to use the | |
19 | plumbing directly very often, but it can be good to know what the | |
20 | plumbing does for when the porcelain isn't flushing. | |
21 | ||
927a503c | 22 | [NOTE] |
a85fecaf BF |
23 | Deeper technical details are often marked as Notes, which you can |
24 | skip on your first reading. | |
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25 | |
26 | ||
27 | Creating a git repository | |
28 | ------------------------- | |
29 | ||
30 | Creating a new git repository couldn't be easier: all git repositories start | |
31 | out empty, and the only thing you need to do is find yourself a | |
32 | subdirectory that you want to use as a working tree - either an empty | |
33 | one for a totally new project, or an existing working tree that you want | |
a6080a0a | 34 | to import into git. |
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35 | |
36 | For our first example, we're going to start a totally new repository from | |
37 | scratch, with no pre-existing files, and we'll call it `git-tutorial`. | |
38 | To start up, create a subdirectory for it, change into that | |
5c94f87e | 39 | subdirectory, and initialize the git infrastructure with `git-init`: |
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40 | |
41 | ------------------------------------------------ | |
42 | $ mkdir git-tutorial | |
43 | $ cd git-tutorial | |
5c94f87e | 44 | $ git-init |
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45 | ------------------------------------------------ |
46 | ||
47 | to which git will reply | |
48 | ||
49 | ---------------- | |
ef0a89a6 | 50 | Initialized empty Git repository in .git/ |
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51 | ---------------- |
52 | ||
53 | which is just git's way of saying that you haven't been doing anything | |
54 | strange, and that it will have created a local `.git` directory setup for | |
55 | your new project. You will now have a `.git` directory, and you can | |
56 | inspect that with `ls`. For your new empty project, it should show you | |
57 | three entries, among other things: | |
58 | ||
960c7021 JH |
59 | - a file called `HEAD`, that has `ref: refs/heads/master` in it. |
60 | This is similar to a symbolic link and points at | |
61 | `refs/heads/master` relative to the `HEAD` file. | |
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62 | + |
63 | Don't worry about the fact that the file that the `HEAD` link points to | |
64 | doesn't even exist yet -- you haven't created the commit that will | |
65 | start your `HEAD` development branch yet. | |
66 | ||
67 | - a subdirectory called `objects`, which will contain all the | |
68 | objects of your project. You should never have any real reason to | |
69 | look at the objects directly, but you might want to know that these | |
70 | objects are what contains all the real 'data' in your repository. | |
71 | ||
72 | - a subdirectory called `refs`, which contains references to objects. | |
73 | ||
74 | In particular, the `refs` subdirectory will contain two other | |
75 | subdirectories, named `heads` and `tags` respectively. They do | |
76 | exactly what their names imply: they contain references to any number | |
77 | of different 'heads' of development (aka 'branches'), and to any | |
78 | 'tags' that you have created to name specific versions in your | |
79 | repository. | |
80 | ||
81 | One note: the special `master` head is the default branch, which is | |
960c7021 | 82 | why the `.git/HEAD` file was created points to it even if it |
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83 | doesn't yet exist. Basically, the `HEAD` link is supposed to always |
84 | point to the branch you are working on right now, and you always | |
85 | start out expecting to work on the `master` branch. | |
86 | ||
87 | However, this is only a convention, and you can name your branches | |
88 | anything you want, and don't have to ever even 'have' a `master` | |
89 | branch. A number of the git tools will assume that `.git/HEAD` is | |
90 | valid, though. | |
91 | ||
92 | [NOTE] | |
93 | An 'object' is identified by its 160-bit SHA1 hash, aka 'object name', | |
94 | and a reference to an object is always the 40-byte hex | |
95 | representation of that SHA1 name. The files in the `refs` | |
96 | subdirectory are expected to contain these hex references | |
97 | (usually with a final `\'\n\'` at the end), and you should thus | |
98 | expect to see a number of 41-byte files containing these | |
99 | references in these `refs` subdirectories when you actually start | |
100 | populating your tree. | |
101 | ||
102 | [NOTE] | |
103 | An advanced user may want to take a look at the | |
104 | link:repository-layout.html[repository layout] document | |
105 | after finishing this tutorial. | |
106 | ||
107 | You have now created your first git repository. Of course, since it's | |
108 | empty, that's not very useful, so let's start populating it with data. | |
109 | ||
110 | ||
111 | Populating a git repository | |
112 | --------------------------- | |
113 | ||
114 | We'll keep this simple and stupid, so we'll start off with populating a | |
115 | few trivial files just to get a feel for it. | |
116 | ||
117 | Start off with just creating any random files that you want to maintain | |
118 | in your git repository. We'll start off with a few bad examples, just to | |
119 | get a feel for how this works: | |
120 | ||
121 | ------------------------------------------------ | |
122 | $ echo "Hello World" >hello | |
123 | $ echo "Silly example" >example | |
124 | ------------------------------------------------ | |
125 | ||
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126 | you have now created two files in your working tree (aka 'working directory'), |
127 | but to actually check in your hard work, you will have to go through two steps: | |
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128 | |
129 | - fill in the 'index' file (aka 'cache') with the information about your | |
130 | working tree state. | |
131 | ||
132 | - commit that index file as an object. | |
133 | ||
134 | The first step is trivial: when you want to tell git about any changes | |
135 | to your working tree, you use the `git-update-index` program. That | |
136 | program normally just takes a list of filenames you want to update, but | |
137 | to avoid trivial mistakes, it refuses to add new entries to the index | |
138 | (or remove existing ones) unless you explicitly tell it that you're | |
139 | adding a new entry with the `\--add` flag (or removing an entry with the | |
140 | `\--remove`) flag. | |
141 | ||
142 | So to populate the index with the two files you just created, you can do | |
143 | ||
144 | ------------------------------------------------ | |
145 | $ git-update-index --add hello example | |
146 | ------------------------------------------------ | |
147 | ||
148 | and you have now told git to track those two files. | |
149 | ||
150 | In fact, as you did that, if you now look into your object directory, | |
151 | you'll notice that git will have added two new objects to the object | |
152 | database. If you did exactly the steps above, you should now be able to do | |
153 | ||
154 | ||
155 | ---------------- | |
156 | $ ls .git/objects/??/* | |
157 | ---------------- | |
158 | ||
159 | and see two files: | |
160 | ||
161 | ---------------- | |
a6080a0a | 162 | .git/objects/55/7db03de997c86a4a028e1ebd3a1ceb225be238 |
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163 | .git/objects/f2/4c74a2e500f5ee1332c86b94199f52b1d1d962 |
164 | ---------------- | |
165 | ||
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166 | which correspond with the objects with names of `557db...` and |
167 | `f24c7...` respectively. | |
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168 | |
169 | If you want to, you can use `git-cat-file` to look at those objects, but | |
170 | you'll have to use the object name, not the filename of the object: | |
171 | ||
172 | ---------------- | |
173 | $ git-cat-file -t 557db03de997c86a4a028e1ebd3a1ceb225be238 | |
174 | ---------------- | |
175 | ||
176 | where the `-t` tells `git-cat-file` to tell you what the "type" of the | |
abda1ef5 | 177 | object is. git will tell you that you have a "blob" object (i.e., just a |
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178 | regular file), and you can see the contents with |
179 | ||
180 | ---------------- | |
181 | $ git-cat-file "blob" 557db03 | |
182 | ---------------- | |
183 | ||
960c7021 | 184 | which will print out "Hello World". The object `557db03` is nothing |
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185 | more than the contents of your file `hello`. |
186 | ||
187 | [NOTE] | |
188 | Don't confuse that object with the file `hello` itself. The | |
189 | object is literally just those specific *contents* of the file, and | |
190 | however much you later change the contents in file `hello`, the object | |
191 | we just looked at will never change. Objects are immutable. | |
192 | ||
193 | [NOTE] | |
194 | The second example demonstrates that you can | |
195 | abbreviate the object name to only the first several | |
196 | hexadecimal digits in most places. | |
197 | ||
198 | Anyway, as we mentioned previously, you normally never actually take a | |
199 | look at the objects themselves, and typing long 40-character hex | |
200 | names is not something you'd normally want to do. The above digression | |
201 | was just to show that `git-update-index` did something magical, and | |
202 | actually saved away the contents of your files into the git object | |
203 | database. | |
204 | ||
205 | Updating the index did something else too: it created a `.git/index` | |
206 | file. This is the index that describes your current working tree, and | |
207 | something you should be very aware of. Again, you normally never worry | |
208 | about the index file itself, but you should be aware of the fact that | |
209 | you have not actually really "checked in" your files into git so far, | |
210 | you've only *told* git about them. | |
211 | ||
212 | However, since git knows about them, you can now start using some of the | |
a6080a0a | 213 | most basic git commands to manipulate the files or look at their status. |
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214 | |
215 | In particular, let's not even check in the two files into git yet, we'll | |
216 | start off by adding another line to `hello` first: | |
217 | ||
218 | ------------------------------------------------ | |
219 | $ echo "It's a new day for git" >>hello | |
220 | ------------------------------------------------ | |
221 | ||
222 | and you can now, since you told git about the previous state of `hello`, ask | |
223 | git what has changed in the tree compared to your old index, using the | |
224 | `git-diff-files` command: | |
225 | ||
226 | ------------ | |
227 | $ git-diff-files | |
228 | ------------ | |
229 | ||
230 | Oops. That wasn't very readable. It just spit out its own internal | |
231 | version of a `diff`, but that internal version really just tells you | |
232 | that it has noticed that "hello" has been modified, and that the old object | |
233 | contents it had have been replaced with something else. | |
234 | ||
235 | To make it readable, we can tell git-diff-files to output the | |
236 | differences as a patch, using the `-p` flag: | |
237 | ||
238 | ------------ | |
239 | $ git-diff-files -p | |
240 | diff --git a/hello b/hello | |
241 | index 557db03..263414f 100644 | |
242 | --- a/hello | |
243 | +++ b/hello | |
244 | @@ -1 +1,2 @@ | |
245 | Hello World | |
246 | +It's a new day for git | |
247 | ---- | |
248 | ||
249 | i.e. the diff of the change we caused by adding another line to `hello`. | |
250 | ||
251 | In other words, `git-diff-files` always shows us the difference between | |
252 | what is recorded in the index, and what is currently in the working | |
253 | tree. That's very useful. | |
254 | ||
255 | A common shorthand for `git-diff-files -p` is to just write `git | |
256 | diff`, which will do the same thing. | |
257 | ||
258 | ------------ | |
259 | $ git diff | |
260 | diff --git a/hello b/hello | |
261 | index 557db03..263414f 100644 | |
262 | --- a/hello | |
263 | +++ b/hello | |
264 | @@ -1 +1,2 @@ | |
265 | Hello World | |
266 | +It's a new day for git | |
267 | ------------ | |
268 | ||
269 | ||
270 | Committing git state | |
271 | -------------------- | |
272 | ||
273 | Now, we want to go to the next stage in git, which is to take the files | |
274 | that git knows about in the index, and commit them as a real tree. We do | |
275 | that in two phases: creating a 'tree' object, and committing that 'tree' | |
276 | object as a 'commit' object together with an explanation of what the | |
277 | tree was all about, along with information of how we came to that state. | |
278 | ||
279 | Creating a tree object is trivial, and is done with `git-write-tree`. | |
280 | There are no options or other input: git-write-tree will take the | |
281 | current index state, and write an object that describes that whole | |
282 | index. In other words, we're now tying together all the different | |
283 | filenames with their contents (and their permissions), and we're | |
284 | creating the equivalent of a git "directory" object: | |
285 | ||
286 | ------------------------------------------------ | |
287 | $ git-write-tree | |
288 | ------------------------------------------------ | |
289 | ||
290 | and this will just output the name of the resulting tree, in this case | |
291 | (if you have done exactly as I've described) it should be | |
292 | ||
293 | ---------------- | |
294 | 8988da15d077d4829fc51d8544c097def6644dbb | |
295 | ---------------- | |
296 | ||
297 | which is another incomprehensible object name. Again, if you want to, | |
298 | you can use `git-cat-file -t 8988d\...` to see that this time the object | |
299 | is not a "blob" object, but a "tree" object (you can also use | |
300 | `git-cat-file` to actually output the raw object contents, but you'll see | |
301 | mainly a binary mess, so that's less interesting). | |
302 | ||
303 | However -- normally you'd never use `git-write-tree` on its own, because | |
304 | normally you always commit a tree into a commit object using the | |
305 | `git-commit-tree` command. In fact, it's easier to not actually use | |
306 | `git-write-tree` on its own at all, but to just pass its result in as an | |
307 | argument to `git-commit-tree`. | |
308 | ||
309 | `git-commit-tree` normally takes several arguments -- it wants to know | |
310 | what the 'parent' of a commit was, but since this is the first commit | |
311 | ever in this new repository, and it has no parents, we only need to pass in | |
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312 | the object name of the tree. However, `git-commit-tree` also wants to get a |
313 | commit message on its standard input, and it will write out the resulting | |
314 | object name for the commit to its standard output. | |
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315 | |
316 | And this is where we create the `.git/refs/heads/master` file | |
317 | which is pointed at by `HEAD`. This file is supposed to contain | |
318 | the reference to the top-of-tree of the master branch, and since | |
319 | that's exactly what `git-commit-tree` spits out, we can do this | |
320 | all with a sequence of simple shell commands: | |
321 | ||
322 | ------------------------------------------------ | |
323 | $ tree=$(git-write-tree) | |
324 | $ commit=$(echo 'Initial commit' | git-commit-tree $tree) | |
325 | $ git-update-ref HEAD $commit | |
326 | ------------------------------------------------ | |
327 | ||
ebd124c6 NP |
328 | In this case this creates a totally new commit that is not related to |
329 | anything else. Normally you do this only *once* for a project ever, and | |
330 | all later commits will be parented on top of an earlier commit. | |
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331 | |
332 | Again, normally you'd never actually do this by hand. There is a | |
333 | helpful script called `git commit` that will do all of this for you. So | |
334 | you could have just written `git commit` | |
335 | instead, and it would have done the above magic scripting for you. | |
336 | ||
337 | ||
338 | Making a change | |
339 | --------------- | |
340 | ||
341 | Remember how we did the `git-update-index` on file `hello` and then we | |
342 | changed `hello` afterward, and could compare the new state of `hello` with the | |
a6080a0a | 343 | state we saved in the index file? |
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344 | |
345 | Further, remember how I said that `git-write-tree` writes the contents | |
346 | of the *index* file to the tree, and thus what we just committed was in | |
347 | fact the *original* contents of the file `hello`, not the new ones. We did | |
348 | that on purpose, to show the difference between the index state, and the | |
349 | state in the working tree, and how they don't have to match, even | |
350 | when we commit things. | |
351 | ||
352 | As before, if we do `git-diff-files -p` in our git-tutorial project, | |
353 | we'll still see the same difference we saw last time: the index file | |
354 | hasn't changed by the act of committing anything. However, now that we | |
355 | have committed something, we can also learn to use a new command: | |
356 | `git-diff-index`. | |
357 | ||
358 | Unlike `git-diff-files`, which showed the difference between the index | |
359 | file and the working tree, `git-diff-index` shows the differences | |
360 | between a committed *tree* and either the index file or the working | |
361 | tree. In other words, `git-diff-index` wants a tree to be diffed | |
362 | against, and before we did the commit, we couldn't do that, because we | |
a6080a0a | 363 | didn't have anything to diff against. |
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364 | |
365 | But now we can do | |
366 | ||
367 | ---------------- | |
368 | $ git-diff-index -p HEAD | |
369 | ---------------- | |
370 | ||
371 | (where `-p` has the same meaning as it did in `git-diff-files`), and it | |
a6080a0a | 372 | will show us the same difference, but for a totally different reason. |
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373 | Now we're comparing the working tree not against the index file, |
374 | but against the tree we just wrote. It just so happens that those two | |
375 | are obviously the same, so we get the same result. | |
376 | ||
377 | Again, because this is a common operation, you can also just shorthand | |
378 | it with | |
379 | ||
380 | ---------------- | |
381 | $ git diff HEAD | |
382 | ---------------- | |
383 | ||
384 | which ends up doing the above for you. | |
385 | ||
386 | In other words, `git-diff-index` normally compares a tree against the | |
387 | working tree, but when given the `\--cached` flag, it is told to | |
388 | instead compare against just the index cache contents, and ignore the | |
389 | current working tree state entirely. Since we just wrote the index | |
390 | file to HEAD, doing `git-diff-index \--cached -p HEAD` should thus return | |
a6080a0a | 391 | an empty set of differences, and that's exactly what it does. |
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392 | |
393 | [NOTE] | |
394 | ================ | |
395 | `git-diff-index` really always uses the index for its | |
396 | comparisons, and saying that it compares a tree against the working | |
397 | tree is thus not strictly accurate. In particular, the list of | |
398 | files to compare (the "meta-data") *always* comes from the index file, | |
399 | regardless of whether the `\--cached` flag is used or not. The `\--cached` | |
400 | flag really only determines whether the file *contents* to be compared | |
401 | come from the working tree or not. | |
402 | ||
403 | This is not hard to understand, as soon as you realize that git simply | |
404 | never knows (or cares) about files that it is not told about | |
405 | explicitly. git will never go *looking* for files to compare, it | |
406 | expects you to tell it what the files are, and that's what the index | |
407 | is there for. | |
408 | ================ | |
409 | ||
410 | However, our next step is to commit the *change* we did, and again, to | |
411 | understand what's going on, keep in mind the difference between "working | |
412 | tree contents", "index file" and "committed tree". We have changes | |
413 | in the working tree that we want to commit, and we always have to | |
414 | work through the index file, so the first thing we need to do is to | |
415 | update the index cache: | |
416 | ||
417 | ------------------------------------------------ | |
418 | $ git-update-index hello | |
419 | ------------------------------------------------ | |
420 | ||
421 | (note how we didn't need the `\--add` flag this time, since git knew | |
422 | about the file already). | |
423 | ||
424 | Note what happens to the different `git-diff-\*` versions here. After | |
425 | we've updated `hello` in the index, `git-diff-files -p` now shows no | |
426 | differences, but `git-diff-index -p HEAD` still *does* show that the | |
427 | current state is different from the state we committed. In fact, now | |
428 | `git-diff-index` shows the same difference whether we use the `--cached` | |
429 | flag or not, since now the index is coherent with the working tree. | |
430 | ||
431 | Now, since we've updated `hello` in the index, we can commit the new | |
432 | version. We could do it by writing the tree by hand again, and | |
433 | committing the tree (this time we'd have to use the `-p HEAD` flag to | |
434 | tell commit that the HEAD was the *parent* of the new commit, and that | |
435 | this wasn't an initial commit any more), but you've done that once | |
436 | already, so let's just use the helpful script this time: | |
437 | ||
438 | ------------------------------------------------ | |
439 | $ git commit | |
440 | ------------------------------------------------ | |
441 | ||
442 | which starts an editor for you to write the commit message and tells you | |
443 | a bit about what you have done. | |
444 | ||
445 | Write whatever message you want, and all the lines that start with '#' | |
446 | will be pruned out, and the rest will be used as the commit message for | |
447 | the change. If you decide you don't want to commit anything after all at | |
448 | this point (you can continue to edit things and update the index), you | |
449 | can just leave an empty message. Otherwise `git commit` will commit | |
450 | the change for you. | |
451 | ||
452 | You've now made your first real git commit. And if you're interested in | |
453 | looking at what `git commit` really does, feel free to investigate: | |
454 | it's a few very simple shell scripts to generate the helpful (?) commit | |
455 | message headers, and a few one-liners that actually do the | |
456 | commit itself (`git-commit`). | |
457 | ||
458 | ||
459 | Inspecting Changes | |
460 | ------------------ | |
461 | ||
462 | While creating changes is useful, it's even more useful if you can tell | |
463 | later what changed. The most useful command for this is another of the | |
464 | `diff` family, namely `git-diff-tree`. | |
465 | ||
466 | `git-diff-tree` can be given two arbitrary trees, and it will tell you the | |
467 | differences between them. Perhaps even more commonly, though, you can | |
468 | give it just a single commit object, and it will figure out the parent | |
469 | of that commit itself, and show the difference directly. Thus, to get | |
470 | the same diff that we've already seen several times, we can now do | |
471 | ||
472 | ---------------- | |
473 | $ git-diff-tree -p HEAD | |
474 | ---------------- | |
475 | ||
476 | (again, `-p` means to show the difference as a human-readable patch), | |
477 | and it will show what the last commit (in `HEAD`) actually changed. | |
478 | ||
479 | [NOTE] | |
480 | ============ | |
481 | Here is an ASCII art by Jon Loeliger that illustrates how | |
482 | various diff-\* commands compare things. | |
483 | ||
484 | diff-tree | |
485 | +----+ | |
486 | | | | |
487 | | | | |
488 | V V | |
489 | +-----------+ | |
490 | | Object DB | | |
491 | | Backing | | |
492 | | Store | | |
493 | +-----------+ | |
494 | ^ ^ | |
495 | | | | |
496 | | | diff-index --cached | |
497 | | | | |
498 | diff-index | V | |
499 | | +-----------+ | |
500 | | | Index | | |
501 | | | "cache" | | |
502 | | +-----------+ | |
503 | | ^ | |
504 | | | | |
505 | | | diff-files | |
506 | | | | |
507 | V V | |
508 | +-----------+ | |
509 | | Working | | |
510 | | Directory | | |
511 | +-----------+ | |
512 | ============ | |
513 | ||
960c7021 JH |
514 | More interestingly, you can also give `git-diff-tree` the `--pretty` flag, |
515 | which tells it to also show the commit message and author and date of the | |
927a503c BF |
516 | commit, and you can tell it to show a whole series of diffs. |
517 | Alternatively, you can tell it to be "silent", and not show the diffs at | |
518 | all, but just show the actual commit message. | |
519 | ||
520 | In fact, together with the `git-rev-list` program (which generates a | |
521 | list of revisions), `git-diff-tree` ends up being a veritable fount of | |
522 | changes. A trivial (but very useful) script called `git-whatchanged` is | |
523 | included with git which does exactly this, and shows a log of recent | |
524 | activities. | |
525 | ||
526 | To see the whole history of our pitiful little git-tutorial project, you | |
527 | can do | |
528 | ||
529 | ---------------- | |
530 | $ git log | |
531 | ---------------- | |
532 | ||
533 | which shows just the log messages, or if we want to see the log together | |
534 | with the associated patches use the more complex (and much more | |
535 | powerful) | |
536 | ||
537 | ---------------- | |
538 | $ git-whatchanged -p --root | |
539 | ---------------- | |
540 | ||
541 | and you will see exactly what has changed in the repository over its | |
a6080a0a | 542 | short history. |
927a503c BF |
543 | |
544 | [NOTE] | |
545 | The `\--root` flag is a flag to `git-diff-tree` to tell it to | |
546 | show the initial aka 'root' commit too. Normally you'd probably not | |
547 | want to see the initial import diff, but since the tutorial project | |
548 | was started from scratch and is so small, we use it to make the result | |
549 | a bit more interesting. | |
550 | ||
551 | With that, you should now be having some inkling of what git does, and | |
552 | can explore on your own. | |
553 | ||
554 | [NOTE] | |
555 | Most likely, you are not directly using the core | |
3b27428b BS |
556 | git Plumbing commands, but using Porcelain such as `git-add`, `git-rm' |
557 | and `git-commit'. | |
927a503c BF |
558 | |
559 | ||
560 | Tagging a version | |
561 | ----------------- | |
562 | ||
563 | In git, there are two kinds of tags, a "light" one, and an "annotated tag". | |
564 | ||
565 | A "light" tag is technically nothing more than a branch, except we put | |
566 | it in the `.git/refs/tags/` subdirectory instead of calling it a `head`. | |
567 | So the simplest form of tag involves nothing more than | |
568 | ||
569 | ------------------------------------------------ | |
570 | $ git tag my-first-tag | |
571 | ------------------------------------------------ | |
572 | ||
573 | which just writes the current `HEAD` into the `.git/refs/tags/my-first-tag` | |
574 | file, after which point you can then use this symbolic name for that | |
575 | particular state. You can, for example, do | |
576 | ||
577 | ---------------- | |
578 | $ git diff my-first-tag | |
579 | ---------------- | |
580 | ||
5221ecbc | 581 | to diff your current state against that tag which at this point will |
927a503c BF |
582 | obviously be an empty diff, but if you continue to develop and commit |
583 | stuff, you can use your tag as an "anchor-point" to see what has changed | |
584 | since you tagged it. | |
585 | ||
586 | An "annotated tag" is actually a real git object, and contains not only a | |
587 | pointer to the state you want to tag, but also a small tag name and | |
588 | message, along with optionally a PGP signature that says that yes, | |
589 | you really did | |
590 | that tag. You create these annotated tags with either the `-a` or | |
591 | `-s` flag to `git tag`: | |
592 | ||
593 | ---------------- | |
594 | $ git tag -s <tagname> | |
595 | ---------------- | |
596 | ||
597 | which will sign the current `HEAD` (but you can also give it another | |
abda1ef5 | 598 | argument that specifies the thing to tag, i.e., you could have tagged the |
927a503c BF |
599 | current `mybranch` point by using `git tag <tagname> mybranch`). |
600 | ||
601 | You normally only do signed tags for major releases or things | |
602 | like that, while the light-weight tags are useful for any marking you | |
603 | want to do -- any time you decide that you want to remember a certain | |
604 | point, just create a private tag for it, and you have a nice symbolic | |
605 | name for the state at that point. | |
606 | ||
607 | ||
608 | Copying repositories | |
609 | -------------------- | |
610 | ||
aacd404e | 611 | git repositories are normally totally self-sufficient and relocatable. |
927a503c BF |
612 | Unlike CVS, for example, there is no separate notion of |
613 | "repository" and "working tree". A git repository normally *is* the | |
614 | working tree, with the local git information hidden in the `.git` | |
615 | subdirectory. There is nothing else. What you see is what you got. | |
616 | ||
617 | [NOTE] | |
618 | You can tell git to split the git internal information from | |
619 | the directory that it tracks, but we'll ignore that for now: it's not | |
620 | how normal projects work, and it's really only meant for special uses. | |
621 | So the mental model of "the git information is always tied directly to | |
622 | the working tree that it describes" may not be technically 100% | |
623 | accurate, but it's a good model for all normal use. | |
624 | ||
a6080a0a | 625 | This has two implications: |
927a503c BF |
626 | |
627 | - if you grow bored with the tutorial repository you created (or you've | |
628 | made a mistake and want to start all over), you can just do simple | |
629 | + | |
630 | ---------------- | |
631 | $ rm -rf git-tutorial | |
632 | ---------------- | |
633 | + | |
634 | and it will be gone. There's no external repository, and there's no | |
635 | history outside the project you created. | |
636 | ||
637 | - if you want to move or duplicate a git repository, you can do so. There | |
638 | is `git clone` command, but if all you want to do is just to | |
639 | create a copy of your repository (with all the full history that | |
640 | went along with it), you can do so with a regular | |
641 | `cp -a git-tutorial new-git-tutorial`. | |
642 | + | |
643 | Note that when you've moved or copied a git repository, your git index | |
644 | file (which caches various information, notably some of the "stat" | |
645 | information for the files involved) will likely need to be refreshed. | |
646 | So after you do a `cp -a` to create a new copy, you'll want to do | |
647 | + | |
648 | ---------------- | |
649 | $ git-update-index --refresh | |
650 | ---------------- | |
651 | + | |
652 | in the new repository to make sure that the index file is up-to-date. | |
653 | ||
654 | Note that the second point is true even across machines. You can | |
655 | duplicate a remote git repository with *any* regular copy mechanism, be it | |
656 | `scp`, `rsync` or `wget`. | |
657 | ||
658 | When copying a remote repository, you'll want to at a minimum update the | |
659 | index cache when you do this, and especially with other peoples' | |
660 | repositories you often want to make sure that the index cache is in some | |
661 | known state (you don't know *what* they've done and not yet checked in), | |
662 | so usually you'll precede the `git-update-index` with a | |
663 | ||
664 | ---------------- | |
665 | $ git-read-tree --reset HEAD | |
666 | $ git-update-index --refresh | |
667 | ---------------- | |
668 | ||
669 | which will force a total index re-build from the tree pointed to by `HEAD`. | |
670 | It resets the index contents to `HEAD`, and then the `git-update-index` | |
671 | makes sure to match up all index entries with the checked-out files. | |
672 | If the original repository had uncommitted changes in its | |
673 | working tree, `git-update-index --refresh` notices them and | |
674 | tells you they need to be updated. | |
675 | ||
676 | The above can also be written as simply | |
677 | ||
678 | ---------------- | |
679 | $ git reset | |
680 | ---------------- | |
681 | ||
682 | and in fact a lot of the common git command combinations can be scripted | |
683 | with the `git xyz` interfaces. You can learn things by just looking | |
3b27428b BS |
684 | at what the various git scripts do. For example, `git reset` used to be |
685 | the above two lines implemented in `git-reset`, but some things like | |
927a503c BF |
686 | `git status` and `git commit` are slightly more complex scripts around |
687 | the basic git commands. | |
688 | ||
689 | Many (most?) public remote repositories will not contain any of | |
690 | the checked out files or even an index file, and will *only* contain the | |
691 | actual core git files. Such a repository usually doesn't even have the | |
692 | `.git` subdirectory, but has all the git files directly in the | |
a6080a0a | 693 | repository. |
927a503c BF |
694 | |
695 | To create your own local live copy of such a "raw" git repository, you'd | |
696 | first create your own subdirectory for the project, and then copy the | |
697 | raw repository contents into the `.git` directory. For example, to | |
698 | create your own copy of the git repository, you'd do the following | |
699 | ||
700 | ---------------- | |
701 | $ mkdir my-git | |
702 | $ cd my-git | |
703 | $ rsync -rL rsync://rsync.kernel.org/pub/scm/git/git.git/ .git | |
704 | ---------------- | |
705 | ||
a6080a0a | 706 | followed by |
927a503c BF |
707 | |
708 | ---------------- | |
709 | $ git-read-tree HEAD | |
710 | ---------------- | |
711 | ||
712 | to populate the index. However, now you have populated the index, and | |
713 | you have all the git internal files, but you will notice that you don't | |
714 | actually have any of the working tree files to work on. To get | |
715 | those, you'd check them out with | |
716 | ||
717 | ---------------- | |
718 | $ git-checkout-index -u -a | |
719 | ---------------- | |
720 | ||
721 | where the `-u` flag means that you want the checkout to keep the index | |
722 | up-to-date (so that you don't have to refresh it afterward), and the | |
723 | `-a` flag means "check out all files" (if you have a stale copy or an | |
724 | older version of a checked out tree you may also need to add the `-f` | |
725 | flag first, to tell git-checkout-index to *force* overwriting of any old | |
a6080a0a | 726 | files). |
927a503c BF |
727 | |
728 | Again, this can all be simplified with | |
729 | ||
730 | ---------------- | |
731 | $ git clone rsync://rsync.kernel.org/pub/scm/git/git.git/ my-git | |
732 | $ cd my-git | |
733 | $ git checkout | |
734 | ---------------- | |
735 | ||
736 | which will end up doing all of the above for you. | |
737 | ||
738 | You have now successfully copied somebody else's (mine) remote | |
a6080a0a | 739 | repository, and checked it out. |
927a503c BF |
740 | |
741 | ||
742 | Creating a new branch | |
743 | --------------------- | |
744 | ||
745 | Branches in git are really nothing more than pointers into the git | |
746 | object database from within the `.git/refs/` subdirectory, and as we | |
747 | already discussed, the `HEAD` branch is nothing but a symlink to one of | |
a6080a0a | 748 | these object pointers. |
927a503c BF |
749 | |
750 | You can at any time create a new branch by just picking an arbitrary | |
751 | point in the project history, and just writing the SHA1 name of that | |
752 | object into a file under `.git/refs/heads/`. You can use any filename you | |
753 | want (and indeed, subdirectories), but the convention is that the | |
754 | "normal" branch is called `master`. That's just a convention, though, | |
a6080a0a | 755 | and nothing enforces it. |
927a503c BF |
756 | |
757 | To show that as an example, let's go back to the git-tutorial repository we | |
758 | used earlier, and create a branch in it. You do that by simply just | |
759 | saying that you want to check out a new branch: | |
760 | ||
761 | ------------ | |
762 | $ git checkout -b mybranch | |
763 | ------------ | |
764 | ||
765 | will create a new branch based at the current `HEAD` position, and switch | |
a6080a0a | 766 | to it. |
927a503c BF |
767 | |
768 | [NOTE] | |
769 | ================================================ | |
770 | If you make the decision to start your new branch at some | |
771 | other point in the history than the current `HEAD`, you can do so by | |
772 | just telling `git checkout` what the base of the checkout would be. | |
773 | In other words, if you have an earlier tag or branch, you'd just do | |
774 | ||
775 | ------------ | |
776 | $ git checkout -b mybranch earlier-commit | |
777 | ------------ | |
778 | ||
779 | and it would create the new branch `mybranch` at the earlier commit, | |
780 | and check out the state at that time. | |
781 | ================================================ | |
782 | ||
783 | You can always just jump back to your original `master` branch by doing | |
784 | ||
785 | ------------ | |
786 | $ git checkout master | |
787 | ------------ | |
788 | ||
789 | (or any other branch-name, for that matter) and if you forget which | |
790 | branch you happen to be on, a simple | |
791 | ||
927a503c BF |
792 | ------------ |
793 | $ cat .git/HEAD | |
794 | ------------ | |
795 | ||
960c7021 JH |
796 | will tell you where it's pointing. To get the list of branches |
797 | you have, you can say | |
927a503c BF |
798 | |
799 | ------------ | |
800 | $ git branch | |
801 | ------------ | |
802 | ||
3b27428b BS |
803 | which used to be nothing more than a simple script around `ls .git/refs/heads`. |
804 | There will be an asterisk in front of the branch you are currently on. | |
927a503c BF |
805 | |
806 | Sometimes you may wish to create a new branch _without_ actually | |
807 | checking it out and switching to it. If so, just use the command | |
808 | ||
809 | ------------ | |
810 | $ git branch <branchname> [startingpoint] | |
811 | ------------ | |
812 | ||
a6080a0a | 813 | which will simply _create_ the branch, but will not do anything further. |
927a503c BF |
814 | You can then later -- once you decide that you want to actually develop |
815 | on that branch -- switch to that branch with a regular `git checkout` | |
816 | with the branchname as the argument. | |
817 | ||
818 | ||
819 | Merging two branches | |
820 | -------------------- | |
821 | ||
822 | One of the ideas of having a branch is that you do some (possibly | |
823 | experimental) work in it, and eventually merge it back to the main | |
824 | branch. So assuming you created the above `mybranch` that started out | |
825 | being the same as the original `master` branch, let's make sure we're in | |
826 | that branch, and do some work there. | |
827 | ||
828 | ------------------------------------------------ | |
829 | $ git checkout mybranch | |
830 | $ echo "Work, work, work" >>hello | |
d336fc09 | 831 | $ git commit -m "Some work." -i hello |
927a503c BF |
832 | ------------------------------------------------ |
833 | ||
834 | Here, we just added another line to `hello`, and we used a shorthand for | |
835 | doing both `git-update-index hello` and `git commit` by just giving the | |
960c7021 JH |
836 | filename directly to `git commit`, with an `-i` flag (it tells |
837 | git to 'include' that file in addition to what you have done to | |
838 | the index file so far when making the commit). The `-m` flag is to give the | |
927a503c BF |
839 | commit log message from the command line. |
840 | ||
841 | Now, to make it a bit more interesting, let's assume that somebody else | |
842 | does some work in the original branch, and simulate that by going back | |
843 | to the master branch, and editing the same file differently there: | |
844 | ||
845 | ------------ | |
846 | $ git checkout master | |
847 | ------------ | |
848 | ||
849 | Here, take a moment to look at the contents of `hello`, and notice how they | |
850 | don't contain the work we just did in `mybranch` -- because that work | |
851 | hasn't happened in the `master` branch at all. Then do | |
852 | ||
853 | ------------ | |
854 | $ echo "Play, play, play" >>hello | |
855 | $ echo "Lots of fun" >>example | |
d336fc09 | 856 | $ git commit -m "Some fun." -i hello example |
927a503c BF |
857 | ------------ |
858 | ||
859 | since the master branch is obviously in a much better mood. | |
860 | ||
861 | Now, you've got two branches, and you decide that you want to merge the | |
862 | work done. Before we do that, let's introduce a cool graphical tool that | |
863 | helps you view what's going on: | |
864 | ||
865 | ---------------- | |
866 | $ gitk --all | |
867 | ---------------- | |
868 | ||
869 | will show you graphically both of your branches (that's what the `\--all` | |
870 | means: normally it will just show you your current `HEAD`) and their | |
871 | histories. You can also see exactly how they came to be from a common | |
a6080a0a | 872 | source. |
927a503c BF |
873 | |
874 | Anyway, let's exit `gitk` (`^Q` or the File menu), and decide that we want | |
875 | to merge the work we did on the `mybranch` branch into the `master` | |
876 | branch (which is currently our `HEAD` too). To do that, there's a nice | |
877 | script called `git merge`, which wants to know which branches you want | |
878 | to resolve and what the merge is all about: | |
879 | ||
880 | ------------ | |
ba17892d | 881 | $ git merge -m "Merge work in mybranch" mybranch |
927a503c BF |
882 | ------------ |
883 | ||
884 | where the first argument is going to be used as the commit message if | |
885 | the merge can be resolved automatically. | |
886 | ||
887 | Now, in this case we've intentionally created a situation where the | |
888 | merge will need to be fixed up by hand, though, so git will do as much | |
889 | of it as it can automatically (which in this case is just merge the `example` | |
890 | file, which had no differences in the `mybranch` branch), and say: | |
891 | ||
892 | ---------------- | |
a6080a0a JH |
893 | Auto-merging hello |
894 | CONFLICT (content): Merge conflict in hello | |
960c7021 | 895 | Automatic merge failed; fix up by hand |
927a503c BF |
896 | ---------------- |
897 | ||
5fe3acc4 JH |
898 | It tells you that it did an "Automatic merge", which |
899 | failed due to conflicts in `hello`. | |
927a503c BF |
900 | |
901 | Not to worry. It left the (trivial) conflict in `hello` in the same form you | |
902 | should already be well used to if you've ever used CVS, so let's just | |
903 | open `hello` in our editor (whatever that may be), and fix it up somehow. | |
904 | I'd suggest just making it so that `hello` contains all four lines: | |
905 | ||
906 | ------------ | |
907 | Hello World | |
908 | It's a new day for git | |
909 | Play, play, play | |
910 | Work, work, work | |
911 | ------------ | |
912 | ||
913 | and once you're happy with your manual merge, just do a | |
914 | ||
915 | ------------ | |
130fcca6 | 916 | $ git commit -i hello |
927a503c BF |
917 | ------------ |
918 | ||
919 | which will very loudly warn you that you're now committing a merge | |
920 | (which is correct, so never mind), and you can write a small merge | |
921 | message about your adventures in git-merge-land. | |
922 | ||
923 | After you're done, start up `gitk \--all` to see graphically what the | |
924 | history looks like. Notice that `mybranch` still exists, and you can | |
925 | switch to it, and continue to work with it if you want to. The | |
926 | `mybranch` branch will not contain the merge, but next time you merge it | |
927 | from the `master` branch, git will know how you merged it, so you'll not | |
928 | have to do _that_ merge again. | |
929 | ||
930 | Another useful tool, especially if you do not always work in X-Window | |
931 | environment, is `git show-branch`. | |
932 | ||
933 | ------------------------------------------------ | |
2782c935 | 934 | $ git-show-branch --topo-order --more=1 master mybranch |
927a503c BF |
935 | * [master] Merge work in mybranch |
936 | ! [mybranch] Some work. | |
937 | -- | |
938 | - [master] Merge work in mybranch | |
939 | *+ [mybranch] Some work. | |
2782c935 | 940 | * [master^] Some fun. |
927a503c BF |
941 | ------------------------------------------------ |
942 | ||
943 | The first two lines indicate that it is showing the two branches | |
944 | and the first line of the commit log message from their | |
945 | top-of-the-tree commits, you are currently on `master` branch | |
245f1029 | 946 | (notice the asterisk `\*` character), and the first column for |
927a503c BF |
947 | the later output lines is used to show commits contained in the |
948 | `master` branch, and the second column for the `mybranch` | |
949 | branch. Three commits are shown along with their log messages. | |
950 | All of them have non blank characters in the first column (`*` | |
3b27428b | 951 | shows an ordinary commit on the current branch, `-` is a merge commit), which |
927a503c BF |
952 | means they are now part of the `master` branch. Only the "Some |
953 | work" commit has the plus `+` character in the second column, | |
954 | because `mybranch` has not been merged to incorporate these | |
955 | commits from the master branch. The string inside brackets | |
956 | before the commit log message is a short name you can use to | |
957 | name the commit. In the above example, 'master' and 'mybranch' | |
2782c935 | 958 | are branch heads. 'master^' is the first parent of 'master' |
927a503c BF |
959 | branch head. Please see 'git-rev-parse' documentation if you |
960 | see more complex cases. | |
961 | ||
2782c935 SO |
962 | [NOTE] |
963 | Without the '--more=1' option, 'git-show-branch' would not output the | |
964 | '[master^]' commit, as '[mybranch]' commit is a common ancestor of | |
965 | both 'master' and 'mybranch' tips. Please see 'git-show-branch' | |
966 | documentation for details. | |
967 | ||
968 | [NOTE] | |
969 | If there were more commits on the 'master' branch after the merge, the | |
970 | merge commit itself would not be shown by 'git-show-branch' by | |
971 | default. You would need to provide '--sparse' option to make the | |
972 | merge commit visible in this case. | |
973 | ||
927a503c BF |
974 | Now, let's pretend you are the one who did all the work in |
975 | `mybranch`, and the fruit of your hard work has finally been merged | |
976 | to the `master` branch. Let's go back to `mybranch`, and run | |
207dfa07 | 977 | `git merge` to get the "upstream changes" back to your branch. |
927a503c BF |
978 | |
979 | ------------ | |
980 | $ git checkout mybranch | |
ba17892d | 981 | $ git merge -m "Merge upstream changes." master |
927a503c BF |
982 | ------------ |
983 | ||
984 | This outputs something like this (the actual commit object names | |
985 | would be different) | |
986 | ||
987 | ---------------- | |
988 | Updating from ae3a2da... to a80b4aa.... | |
960c7021 | 989 | Fast forward |
927a503c BF |
990 | example | 1 + |
991 | hello | 1 + | |
992 | 2 files changed, 2 insertions(+), 0 deletions(-) | |
993 | ---------------- | |
994 | ||
995 | Because your branch did not contain anything more than what are | |
207dfa07 | 996 | already merged into the `master` branch, the merge operation did |
927a503c BF |
997 | not actually do a merge. Instead, it just updated the top of |
998 | the tree of your branch to that of the `master` branch. This is | |
999 | often called 'fast forward' merge. | |
1000 | ||
1001 | You can run `gitk \--all` again to see how the commit ancestry | |
1002 | looks like, or run `show-branch`, which tells you this. | |
1003 | ||
1004 | ------------------------------------------------ | |
1005 | $ git show-branch master mybranch | |
1006 | ! [master] Merge work in mybranch | |
1007 | * [mybranch] Merge work in mybranch | |
1008 | -- | |
1009 | -- [master] Merge work in mybranch | |
1010 | ------------------------------------------------ | |
1011 | ||
1012 | ||
1013 | Merging external work | |
1014 | --------------------- | |
1015 | ||
1016 | It's usually much more common that you merge with somebody else than | |
1017 | merging with your own branches, so it's worth pointing out that git | |
1018 | makes that very easy too, and in fact, it's not that different from | |
1019 | doing a `git merge`. In fact, a remote merge ends up being nothing | |
1020 | more than "fetch the work from a remote repository into a temporary tag" | |
1021 | followed by a `git merge`. | |
1022 | ||
1023 | Fetching from a remote repository is done by, unsurprisingly, | |
1024 | `git fetch`: | |
1025 | ||
1026 | ---------------- | |
1027 | $ git fetch <remote-repository> | |
1028 | ---------------- | |
1029 | ||
1030 | One of the following transports can be used to name the | |
1031 | repository to download from: | |
1032 | ||
1033 | Rsync:: | |
1034 | `rsync://remote.machine/path/to/repo.git/` | |
1035 | + | |
1036 | Rsync transport is usable for both uploading and downloading, | |
1037 | but is completely unaware of what git does, and can produce | |
1038 | unexpected results when you download from the public repository | |
1039 | while the repository owner is uploading into it via `rsync` | |
1040 | transport. Most notably, it could update the files under | |
1041 | `refs/` which holds the object name of the topmost commits | |
1042 | before uploading the files in `objects/` -- the downloader would | |
1043 | obtain head commit object name while that object itself is still | |
1044 | not available in the repository. For this reason, it is | |
1045 | considered deprecated. | |
1046 | ||
1047 | SSH:: | |
1048 | `remote.machine:/path/to/repo.git/` or | |
1049 | + | |
1050 | `ssh://remote.machine/path/to/repo.git/` | |
1051 | + | |
1052 | This transport can be used for both uploading and downloading, | |
1053 | and requires you to have a log-in privilege over `ssh` to the | |
1054 | remote machine. It finds out the set of objects the other side | |
1055 | lacks by exchanging the head commits both ends have and | |
1056 | transfers (close to) minimum set of objects. It is by far the | |
1057 | most efficient way to exchange git objects between repositories. | |
1058 | ||
1059 | Local directory:: | |
1060 | `/path/to/repo.git/` | |
1061 | + | |
1062 | This transport is the same as SSH transport but uses `sh` to run | |
1063 | both ends on the local machine instead of running other end on | |
1064 | the remote machine via `ssh`. | |
1065 | ||
1066 | git Native:: | |
1067 | `git://remote.machine/path/to/repo.git/` | |
1068 | + | |
1069 | This transport was designed for anonymous downloading. Like SSH | |
1070 | transport, it finds out the set of objects the downstream side | |
1071 | lacks and transfers (close to) minimum set of objects. | |
1072 | ||
1073 | HTTP(S):: | |
1074 | `http://remote.machine/path/to/repo.git/` | |
1075 | + | |
1076 | Downloader from http and https URL | |
1077 | first obtains the topmost commit object name from the remote site | |
1078 | by looking at the specified refname under `repo.git/refs/` directory, | |
1079 | and then tries to obtain the | |
1080 | commit object by downloading from `repo.git/objects/xx/xxx\...` | |
1081 | using the object name of that commit object. Then it reads the | |
1082 | commit object to find out its parent commits and the associate | |
1083 | tree object; it repeats this process until it gets all the | |
abda1ef5 | 1084 | necessary objects. Because of this behavior, they are |
927a503c BF |
1085 | sometimes also called 'commit walkers'. |
1086 | + | |
1087 | The 'commit walkers' are sometimes also called 'dumb | |
1088 | transports', because they do not require any git aware smart | |
1089 | server like git Native transport does. Any stock HTTP server | |
1090 | that does not even support directory index would suffice. But | |
1091 | you must prepare your repository with `git-update-server-info` | |
1092 | to help dumb transport downloaders. | |
927a503c | 1093 | |
207dfa07 | 1094 | Once you fetch from the remote repository, you `merge` that |
927a503c BF |
1095 | with your current branch. |
1096 | ||
1097 | However -- it's such a common thing to `fetch` and then | |
207dfa07 | 1098 | immediately `merge`, that it's called `git pull`, and you can |
927a503c BF |
1099 | simply do |
1100 | ||
1101 | ---------------- | |
1102 | $ git pull <remote-repository> | |
1103 | ---------------- | |
1104 | ||
1105 | and optionally give a branch-name for the remote end as a second | |
1106 | argument. | |
1107 | ||
1108 | [NOTE] | |
1109 | You could do without using any branches at all, by | |
1110 | keeping as many local repositories as you would like to have | |
1111 | branches, and merging between them with `git pull`, just like | |
1112 | you merge between branches. The advantage of this approach is | |
aacd404e | 1113 | that it lets you keep a set of files for each `branch` checked |
927a503c BF |
1114 | out and you may find it easier to switch back and forth if you |
1115 | juggle multiple lines of development simultaneously. Of | |
1116 | course, you will pay the price of more disk usage to hold | |
1117 | multiple working trees, but disk space is cheap these days. | |
1118 | ||
927a503c BF |
1119 | It is likely that you will be pulling from the same remote |
1120 | repository from time to time. As a short hand, you can store | |
c14261ea NP |
1121 | the remote repository URL in the local repository's config file |
1122 | like this: | |
927a503c BF |
1123 | |
1124 | ------------------------------------------------ | |
e0d10e1c | 1125 | $ git config remote.linus.url http://www.kernel.org/pub/scm/git/git.git/ |
927a503c BF |
1126 | ------------------------------------------------ |
1127 | ||
c14261ea | 1128 | and use the "linus" keyword with `git pull` instead of the full URL. |
927a503c BF |
1129 | |
1130 | Examples. | |
1131 | ||
1132 | . `git pull linus` | |
1133 | . `git pull linus tag v0.99.1` | |
927a503c BF |
1134 | |
1135 | the above are equivalent to: | |
1136 | ||
1137 | . `git pull http://www.kernel.org/pub/scm/git/git.git/ HEAD` | |
1138 | . `git pull http://www.kernel.org/pub/scm/git/git.git/ tag v0.99.1` | |
927a503c BF |
1139 | |
1140 | ||
1141 | How does the merge work? | |
1142 | ------------------------ | |
1143 | ||
1144 | We said this tutorial shows what plumbing does to help you cope | |
1145 | with the porcelain that isn't flushing, but we so far did not | |
1146 | talk about how the merge really works. If you are following | |
1147 | this tutorial the first time, I'd suggest to skip to "Publishing | |
1148 | your work" section and come back here later. | |
1149 | ||
1150 | OK, still with me? To give us an example to look at, let's go | |
1151 | back to the earlier repository with "hello" and "example" file, | |
1152 | and bring ourselves back to the pre-merge state: | |
1153 | ||
1154 | ------------ | |
065c5ac1 | 1155 | $ git show-branch --more=2 master mybranch |
927a503c BF |
1156 | ! [master] Merge work in mybranch |
1157 | * [mybranch] Merge work in mybranch | |
1158 | -- | |
1159 | -- [master] Merge work in mybranch | |
1160 | +* [master^2] Some work. | |
1161 | +* [master^] Some fun. | |
1162 | ------------ | |
1163 | ||
1164 | Remember, before running `git merge`, our `master` head was at | |
1165 | "Some fun." commit, while our `mybranch` head was at "Some | |
1166 | work." commit. | |
1167 | ||
1168 | ------------ | |
1169 | $ git checkout mybranch | |
1170 | $ git reset --hard master^2 | |
1171 | $ git checkout master | |
1172 | $ git reset --hard master^ | |
1173 | ------------ | |
1174 | ||
1175 | After rewinding, the commit structure should look like this: | |
1176 | ||
1177 | ------------ | |
1178 | $ git show-branch | |
1179 | * [master] Some fun. | |
1180 | ! [mybranch] Some work. | |
1181 | -- | |
1182 | + [mybranch] Some work. | |
1183 | * [master] Some fun. | |
1184 | *+ [mybranch^] New day. | |
1185 | ------------ | |
1186 | ||
1187 | Now we are ready to experiment with the merge by hand. | |
1188 | ||
1189 | `git merge` command, when merging two branches, uses 3-way merge | |
1190 | algorithm. First, it finds the common ancestor between them. | |
1191 | The command it uses is `git-merge-base`: | |
1192 | ||
1193 | ------------ | |
1194 | $ mb=$(git-merge-base HEAD mybranch) | |
1195 | ------------ | |
1196 | ||
1197 | The command writes the commit object name of the common ancestor | |
1198 | to the standard output, so we captured its output to a variable, | |
3b27428b | 1199 | because we will be using it in the next step. By the way, the common |
927a503c BF |
1200 | ancestor commit is the "New day." commit in this case. You can |
1201 | tell it by: | |
1202 | ||
1203 | ------------ | |
1204 | $ git-name-rev $mb | |
1205 | my-first-tag | |
1206 | ------------ | |
1207 | ||
1208 | After finding out a common ancestor commit, the second step is | |
1209 | this: | |
1210 | ||
1211 | ------------ | |
1212 | $ git-read-tree -m -u $mb HEAD mybranch | |
1213 | ------------ | |
1214 | ||
1215 | This is the same `git-read-tree` command we have already seen, | |
1216 | but it takes three trees, unlike previous examples. This reads | |
1217 | the contents of each tree into different 'stage' in the index | |
065c5ac1 | 1218 | file (the first tree goes to stage 1, the second to stage 2, |
927a503c BF |
1219 | etc.). After reading three trees into three stages, the paths |
1220 | that are the same in all three stages are 'collapsed' into stage | |
1221 | 0. Also paths that are the same in two of three stages are | |
1222 | collapsed into stage 0, taking the SHA1 from either stage 2 or | |
1223 | stage 3, whichever is different from stage 1 (i.e. only one side | |
1224 | changed from the common ancestor). | |
1225 | ||
1226 | After 'collapsing' operation, paths that are different in three | |
1227 | trees are left in non-zero stages. At this point, you can | |
1228 | inspect the index file with this command: | |
1229 | ||
1230 | ------------ | |
1231 | $ git-ls-files --stage | |
1232 | 100644 7f8b141b65fdcee47321e399a2598a235a032422 0 example | |
1233 | 100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello | |
1234 | 100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello | |
1235 | 100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello | |
1236 | ------------ | |
1237 | ||
1238 | In our example of only two files, we did not have unchanged | |
1239 | files so only 'example' resulted in collapsing, but in real-life | |
1240 | large projects, only small number of files change in one commit, | |
1241 | and this 'collapsing' tends to trivially merge most of the paths | |
1242 | fairly quickly, leaving only a handful the real changes in non-zero | |
1243 | stages. | |
1244 | ||
1245 | To look at only non-zero stages, use `\--unmerged` flag: | |
1246 | ||
1247 | ------------ | |
1248 | $ git-ls-files --unmerged | |
1249 | 100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello | |
1250 | 100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello | |
1251 | 100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello | |
1252 | ------------ | |
1253 | ||
1254 | The next step of merging is to merge these three versions of the | |
1255 | file, using 3-way merge. This is done by giving | |
1256 | `git-merge-one-file` command as one of the arguments to | |
1257 | `git-merge-index` command: | |
1258 | ||
1259 | ------------ | |
1260 | $ git-merge-index git-merge-one-file hello | |
1261 | Auto-merging hello. | |
1262 | merge: warning: conflicts during merge | |
1263 | ERROR: Merge conflict in hello. | |
1264 | fatal: merge program failed | |
1265 | ------------ | |
1266 | ||
1267 | `git-merge-one-file` script is called with parameters to | |
1268 | describe those three versions, and is responsible to leave the | |
1269 | merge results in the working tree. | |
1270 | It is a fairly straightforward shell script, and | |
1271 | eventually calls `merge` program from RCS suite to perform a | |
1272 | file-level 3-way merge. In this case, `merge` detects | |
1273 | conflicts, and the merge result with conflict marks is left in | |
1274 | the working tree.. This can be seen if you run `ls-files | |
1275 | --stage` again at this point: | |
1276 | ||
1277 | ------------ | |
1278 | $ git-ls-files --stage | |
1279 | 100644 7f8b141b65fdcee47321e399a2598a235a032422 0 example | |
1280 | 100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello | |
1281 | 100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello | |
1282 | 100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello | |
1283 | ------------ | |
1284 | ||
1285 | This is the state of the index file and the working file after | |
1286 | `git merge` returns control back to you, leaving the conflicting | |
1287 | merge for you to resolve. Notice that the path `hello` is still | |
1288 | unmerged, and what you see with `git diff` at this point is | |
1289 | differences since stage 2 (i.e. your version). | |
1290 | ||
1291 | ||
1292 | Publishing your work | |
1293 | -------------------- | |
1294 | ||
aacd404e | 1295 | So, we can use somebody else's work from a remote repository, but |
927a503c BF |
1296 | how can *you* prepare a repository to let other people pull from |
1297 | it? | |
1298 | ||
79dbbedd | 1299 | You do your real work in your working tree that has your |
927a503c BF |
1300 | primary repository hanging under it as its `.git` subdirectory. |
1301 | You *could* make that repository accessible remotely and ask | |
1302 | people to pull from it, but in practice that is not the way | |
1303 | things are usually done. A recommended way is to have a public | |
1304 | repository, make it reachable by other people, and when the | |
1305 | changes you made in your primary working tree are in good shape, | |
1306 | update the public repository from it. This is often called | |
1307 | 'pushing'. | |
1308 | ||
1309 | [NOTE] | |
1310 | This public repository could further be mirrored, and that is | |
1311 | how git repositories at `kernel.org` are managed. | |
1312 | ||
1313 | Publishing the changes from your local (private) repository to | |
1314 | your remote (public) repository requires a write privilege on | |
1315 | the remote machine. You need to have an SSH account there to | |
1316 | run a single command, `git-receive-pack`. | |
1317 | ||
1318 | First, you need to create an empty repository on the remote | |
1319 | machine that will house your public repository. This empty | |
1320 | repository will be populated and be kept up-to-date by pushing | |
1321 | into it later. Obviously, this repository creation needs to be | |
1322 | done only once. | |
1323 | ||
1324 | [NOTE] | |
1325 | `git push` uses a pair of programs, | |
1326 | `git-send-pack` on your local machine, and `git-receive-pack` | |
1327 | on the remote machine. The communication between the two over | |
1328 | the network internally uses an SSH connection. | |
1329 | ||
1330 | Your private repository's git directory is usually `.git`, but | |
1331 | your public repository is often named after the project name, | |
1332 | i.e. `<project>.git`. Let's create such a public repository for | |
1333 | project `my-git`. After logging into the remote machine, create | |
1334 | an empty directory: | |
1335 | ||
1336 | ------------ | |
1337 | $ mkdir my-git.git | |
1338 | ------------ | |
1339 | ||
1340 | Then, make that directory into a git repository by running | |
5c94f87e | 1341 | `git init`, but this time, since its name is not the usual |
927a503c BF |
1342 | `.git`, we do things slightly differently: |
1343 | ||
1344 | ------------ | |
5c94f87e | 1345 | $ GIT_DIR=my-git.git git-init |
927a503c BF |
1346 | ------------ |
1347 | ||
1348 | Make sure this directory is available for others you want your | |
1349 | changes to be pulled by via the transport of your choice. Also | |
1350 | you need to make sure that you have the `git-receive-pack` | |
1351 | program on the `$PATH`. | |
1352 | ||
1353 | [NOTE] | |
1354 | Many installations of sshd do not invoke your shell as the login | |
1355 | shell when you directly run programs; what this means is that if | |
1356 | your login shell is `bash`, only `.bashrc` is read and not | |
1357 | `.bash_profile`. As a workaround, make sure `.bashrc` sets up | |
1358 | `$PATH` so that you can run `git-receive-pack` program. | |
1359 | ||
1360 | [NOTE] | |
1361 | If you plan to publish this repository to be accessed over http, | |
1362 | you should do `chmod +x my-git.git/hooks/post-update` at this | |
1363 | point. This makes sure that every time you push into this | |
1364 | repository, `git-update-server-info` is run. | |
1365 | ||
1366 | Your "public repository" is now ready to accept your changes. | |
1367 | Come back to the machine you have your private repository. From | |
1368 | there, run this command: | |
1369 | ||
1370 | ------------ | |
1371 | $ git push <public-host>:/path/to/my-git.git master | |
1372 | ------------ | |
1373 | ||
1374 | This synchronizes your public repository to match the named | |
1375 | branch head (i.e. `master` in this case) and objects reachable | |
1376 | from them in your current repository. | |
1377 | ||
1378 | As a real example, this is how I update my public git | |
1379 | repository. Kernel.org mirror network takes care of the | |
1380 | propagation to other publicly visible machines: | |
1381 | ||
1382 | ------------ | |
a6080a0a | 1383 | $ git push master.kernel.org:/pub/scm/git/git.git/ |
927a503c BF |
1384 | ------------ |
1385 | ||
1386 | ||
1387 | Packing your repository | |
1388 | ----------------------- | |
1389 | ||
1390 | Earlier, we saw that one file under `.git/objects/??/` directory | |
1391 | is stored for each git object you create. This representation | |
1392 | is efficient to create atomically and safely, but | |
1393 | not so convenient to transport over the network. Since git objects are | |
1394 | immutable once they are created, there is a way to optimize the | |
1395 | storage by "packing them together". The command | |
1396 | ||
1397 | ------------ | |
1398 | $ git repack | |
1399 | ------------ | |
1400 | ||
1401 | will do it for you. If you followed the tutorial examples, you | |
1402 | would have accumulated about 17 objects in `.git/objects/??/` | |
1403 | directories by now. `git repack` tells you how many objects it | |
1404 | packed, and stores the packed file in `.git/objects/pack` | |
1405 | directory. | |
1406 | ||
1407 | [NOTE] | |
1408 | You will see two files, `pack-\*.pack` and `pack-\*.idx`, | |
1409 | in `.git/objects/pack` directory. They are closely related to | |
1410 | each other, and if you ever copy them by hand to a different | |
1411 | repository for whatever reason, you should make sure you copy | |
1412 | them together. The former holds all the data from the objects | |
1413 | in the pack, and the latter holds the index for random | |
1414 | access. | |
1415 | ||
1416 | If you are paranoid, running `git-verify-pack` command would | |
1417 | detect if you have a corrupt pack, but do not worry too much. | |
1418 | Our programs are always perfect ;-). | |
1419 | ||
1420 | Once you have packed objects, you do not need to leave the | |
1421 | unpacked objects that are contained in the pack file anymore. | |
1422 | ||
1423 | ------------ | |
1424 | $ git prune-packed | |
1425 | ------------ | |
1426 | ||
1427 | would remove them for you. | |
1428 | ||
1429 | You can try running `find .git/objects -type f` before and after | |
1430 | you run `git prune-packed` if you are curious. Also `git | |
1431 | count-objects` would tell you how many unpacked objects are in | |
1432 | your repository and how much space they are consuming. | |
1433 | ||
1434 | [NOTE] | |
1435 | `git pull` is slightly cumbersome for HTTP transport, as a | |
1436 | packed repository may contain relatively few objects in a | |
1437 | relatively large pack. If you expect many HTTP pulls from your | |
1438 | public repository you might want to repack & prune often, or | |
1439 | never. | |
1440 | ||
1441 | If you run `git repack` again at this point, it will say | |
1442 | "Nothing to pack". Once you continue your development and | |
1443 | accumulate the changes, running `git repack` again will create a | |
1444 | new pack, that contains objects created since you packed your | |
1445 | repository the last time. We recommend that you pack your project | |
1446 | soon after the initial import (unless you are starting your | |
1447 | project from scratch), and then run `git repack` every once in a | |
1448 | while, depending on how active your project is. | |
1449 | ||
1450 | When a repository is synchronized via `git push` and `git pull` | |
1451 | objects packed in the source repository are usually stored | |
1452 | unpacked in the destination, unless rsync transport is used. | |
1453 | While this allows you to use different packing strategies on | |
1454 | both ends, it also means you may need to repack both | |
1455 | repositories every once in a while. | |
1456 | ||
1457 | ||
1458 | Working with Others | |
1459 | ------------------- | |
1460 | ||
1461 | Although git is a truly distributed system, it is often | |
1462 | convenient to organize your project with an informal hierarchy | |
1463 | of developers. Linux kernel development is run this way. There | |
505739f6 | 1464 | is a nice illustration (page 17, "Merges to Mainline") in |
3b27428b | 1465 | link:http://www.xenotime.net/linux/mentor/linux-mentoring-2006.pdf[Randy Dunlap's presentation]. |
927a503c BF |
1466 | |
1467 | It should be stressed that this hierarchy is purely *informal*. | |
1468 | There is nothing fundamental in git that enforces the "chain of | |
1469 | patch flow" this hierarchy implies. You do not have to pull | |
1470 | from only one remote repository. | |
1471 | ||
1472 | A recommended workflow for a "project lead" goes like this: | |
1473 | ||
1474 | 1. Prepare your primary repository on your local machine. Your | |
1475 | work is done there. | |
1476 | ||
1477 | 2. Prepare a public repository accessible to others. | |
1478 | + | |
1479 | If other people are pulling from your repository over dumb | |
1480 | transport protocols (HTTP), you need to keep this repository | |
5c94f87e | 1481 | 'dumb transport friendly'. After `git init`, |
927a503c BF |
1482 | `$GIT_DIR/hooks/post-update` copied from the standard templates |
1483 | would contain a call to `git-update-server-info` but the | |
1484 | `post-update` hook itself is disabled by default -- enable it | |
1485 | with `chmod +x post-update`. This makes sure `git-update-server-info` | |
1486 | keeps the necessary files up-to-date. | |
1487 | ||
1488 | 3. Push into the public repository from your primary | |
1489 | repository. | |
1490 | ||
1491 | 4. `git repack` the public repository. This establishes a big | |
1492 | pack that contains the initial set of objects as the | |
1493 | baseline, and possibly `git prune` if the transport | |
1494 | used for pulling from your repository supports packed | |
1495 | repositories. | |
1496 | ||
1497 | 5. Keep working in your primary repository. Your changes | |
1498 | include modifications of your own, patches you receive via | |
1499 | e-mails, and merges resulting from pulling the "public" | |
1500 | repositories of your "subsystem maintainers". | |
1501 | + | |
1502 | You can repack this private repository whenever you feel like. | |
1503 | ||
1504 | 6. Push your changes to the public repository, and announce it | |
1505 | to the public. | |
1506 | ||
1507 | 7. Every once in a while, "git repack" the public repository. | |
1508 | Go back to step 5. and continue working. | |
1509 | ||
1510 | ||
1511 | A recommended work cycle for a "subsystem maintainer" who works | |
1512 | on that project and has an own "public repository" goes like this: | |
1513 | ||
1514 | 1. Prepare your work repository, by `git clone` the public | |
1515 | repository of the "project lead". The URL used for the | |
c14261ea NP |
1516 | initial cloning is stored in the remote.origin.url |
1517 | configuration variable. | |
927a503c BF |
1518 | |
1519 | 2. Prepare a public repository accessible to others, just like | |
1520 | the "project lead" person does. | |
1521 | ||
1522 | 3. Copy over the packed files from "project lead" public | |
1523 | repository to your public repository, unless the "project | |
1524 | lead" repository lives on the same machine as yours. In the | |
1525 | latter case, you can use `objects/info/alternates` file to | |
1526 | point at the repository you are borrowing from. | |
1527 | ||
1528 | 4. Push into the public repository from your primary | |
1529 | repository. Run `git repack`, and possibly `git prune` if the | |
1530 | transport used for pulling from your repository supports | |
1531 | packed repositories. | |
1532 | ||
1533 | 5. Keep working in your primary repository. Your changes | |
1534 | include modifications of your own, patches you receive via | |
1535 | e-mails, and merges resulting from pulling the "public" | |
1536 | repositories of your "project lead" and possibly your | |
1537 | "sub-subsystem maintainers". | |
1538 | + | |
1539 | You can repack this private repository whenever you feel | |
1540 | like. | |
1541 | ||
1542 | 6. Push your changes to your public repository, and ask your | |
1543 | "project lead" and possibly your "sub-subsystem | |
1544 | maintainers" to pull from it. | |
1545 | ||
1546 | 7. Every once in a while, `git repack` the public repository. | |
1547 | Go back to step 5. and continue working. | |
1548 | ||
1549 | ||
1550 | A recommended work cycle for an "individual developer" who does | |
1551 | not have a "public" repository is somewhat different. It goes | |
1552 | like this: | |
1553 | ||
1554 | 1. Prepare your work repository, by `git clone` the public | |
1555 | repository of the "project lead" (or a "subsystem | |
1556 | maintainer", if you work on a subsystem). The URL used for | |
c14261ea NP |
1557 | the initial cloning is stored in the remote.origin.url |
1558 | configuration variable. | |
927a503c BF |
1559 | |
1560 | 2. Do your work in your repository on 'master' branch. | |
1561 | ||
1562 | 3. Run `git fetch origin` from the public repository of your | |
1563 | upstream every once in a while. This does only the first | |
1564 | half of `git pull` but does not merge. The head of the | |
c14261ea | 1565 | public repository is stored in `.git/refs/remotes/origin/master`. |
927a503c BF |
1566 | |
1567 | 4. Use `git cherry origin` to see which ones of your patches | |
1568 | were accepted, and/or use `git rebase origin` to port your | |
1569 | unmerged changes forward to the updated upstream. | |
1570 | ||
1571 | 5. Use `git format-patch origin` to prepare patches for e-mail | |
1572 | submission to your upstream and send it out. Go back to | |
1573 | step 2. and continue. | |
1574 | ||
1575 | ||
1576 | Working with Others, Shared Repository Style | |
1577 | -------------------------------------------- | |
1578 | ||
1579 | If you are coming from CVS background, the style of cooperation | |
1580 | suggested in the previous section may be new to you. You do not | |
1581 | have to worry. git supports "shared public repository" style of | |
1582 | cooperation you are probably more familiar with as well. | |
1583 | ||
b85c4bbb | 1584 | See link:cvs-migration.html[git for CVS users] for the details. |
927a503c BF |
1585 | |
1586 | Bundling your work together | |
1587 | --------------------------- | |
1588 | ||
1589 | It is likely that you will be working on more than one thing at | |
1590 | a time. It is easy to manage those more-or-less independent tasks | |
1591 | using branches with git. | |
1592 | ||
1593 | We have already seen how branches work previously, | |
1594 | with "fun and work" example using two branches. The idea is the | |
1595 | same if there are more than two branches. Let's say you started | |
1596 | out from "master" head, and have some new code in the "master" | |
1597 | branch, and two independent fixes in the "commit-fix" and | |
1598 | "diff-fix" branches: | |
1599 | ||
1600 | ------------ | |
1601 | $ git show-branch | |
1602 | ! [commit-fix] Fix commit message normalization. | |
1603 | ! [diff-fix] Fix rename detection. | |
1604 | * [master] Release candidate #1 | |
1605 | --- | |
1606 | + [diff-fix] Fix rename detection. | |
1607 | + [diff-fix~1] Better common substring algorithm. | |
1608 | + [commit-fix] Fix commit message normalization. | |
1609 | * [master] Release candidate #1 | |
1610 | ++* [diff-fix~2] Pretty-print messages. | |
1611 | ------------ | |
1612 | ||
1613 | Both fixes are tested well, and at this point, you want to merge | |
1614 | in both of them. You could merge in 'diff-fix' first and then | |
1615 | 'commit-fix' next, like this: | |
1616 | ||
1617 | ------------ | |
d336fc09 SO |
1618 | $ git merge -m "Merge fix in diff-fix" diff-fix |
1619 | $ git merge -m "Merge fix in commit-fix" commit-fix | |
927a503c BF |
1620 | ------------ |
1621 | ||
1622 | Which would result in: | |
1623 | ||
1624 | ------------ | |
1625 | $ git show-branch | |
1626 | ! [commit-fix] Fix commit message normalization. | |
1627 | ! [diff-fix] Fix rename detection. | |
1628 | * [master] Merge fix in commit-fix | |
1629 | --- | |
1630 | - [master] Merge fix in commit-fix | |
1631 | + * [commit-fix] Fix commit message normalization. | |
1632 | - [master~1] Merge fix in diff-fix | |
1633 | +* [diff-fix] Fix rename detection. | |
1634 | +* [diff-fix~1] Better common substring algorithm. | |
1635 | * [master~2] Release candidate #1 | |
1636 | ++* [master~3] Pretty-print messages. | |
1637 | ------------ | |
1638 | ||
1639 | However, there is no particular reason to merge in one branch | |
1640 | first and the other next, when what you have are a set of truly | |
1641 | independent changes (if the order mattered, then they are not | |
1642 | independent by definition). You could instead merge those two | |
1643 | branches into the current branch at once. First let's undo what | |
1644 | we just did and start over. We would want to get the master | |
1645 | branch before these two merges by resetting it to 'master~2': | |
1646 | ||
1647 | ------------ | |
1648 | $ git reset --hard master~2 | |
1649 | ------------ | |
1650 | ||
1651 | You can make sure 'git show-branch' matches the state before | |
1652 | those two 'git merge' you just did. Then, instead of running | |
c14261ea | 1653 | two 'git merge' commands in a row, you would merge these two |
927a503c BF |
1654 | branch heads (this is known as 'making an Octopus'): |
1655 | ||
1656 | ------------ | |
c14261ea | 1657 | $ git merge commit-fix diff-fix |
927a503c BF |
1658 | $ git show-branch |
1659 | ! [commit-fix] Fix commit message normalization. | |
1660 | ! [diff-fix] Fix rename detection. | |
1661 | * [master] Octopus merge of branches 'diff-fix' and 'commit-fix' | |
1662 | --- | |
1663 | - [master] Octopus merge of branches 'diff-fix' and 'commit-fix' | |
1664 | + * [commit-fix] Fix commit message normalization. | |
1665 | +* [diff-fix] Fix rename detection. | |
1666 | +* [diff-fix~1] Better common substring algorithm. | |
1667 | * [master~1] Release candidate #1 | |
1668 | ++* [master~2] Pretty-print messages. | |
1669 | ------------ | |
1670 | ||
1671 | Note that you should not do Octopus because you can. An octopus | |
1672 | is a valid thing to do and often makes it easier to view the | |
c14261ea | 1673 | commit history if you are merging more than two independent |
927a503c BF |
1674 | changes at the same time. However, if you have merge conflicts |
1675 | with any of the branches you are merging in and need to hand | |
1676 | resolve, that is an indication that the development happened in | |
1677 | those branches were not independent after all, and you should | |
1678 | merge two at a time, documenting how you resolved the conflicts, | |
1679 | and the reason why you preferred changes made in one side over | |
1680 | the other. Otherwise it would make the project history harder | |
1681 | to follow, not easier. |