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2cf565c5 DG |
1 | git-read-tree(1) |
2 | ================ | |
2cf565c5 DG |
3 | |
4 | NAME | |
5 | ---- | |
5f3aa197 | 6 | git-read-tree - Reads tree information into the index |
2cf565c5 DG |
7 | |
8 | ||
9 | SYNOPSIS | |
10 | -------- | |
5a56da58 SB |
11 | 'git read-tree' [[-m [--trivial] [--aggressive] | --reset | --prefix=<prefix>] |
12 | [-u [--exclude-per-directory=<gitignore>] | -i]] | |
a5d07d0f | 13 | [--index-output=<file>] [--no-sparse-checkout] |
fb1bb965 | 14 | (--empty | <tree-ish1> [<tree-ish2> [<tree-ish3>]]) |
ccef66b5 | 15 | |
2cf565c5 DG |
16 | |
17 | DESCRIPTION | |
18 | ----------- | |
5f3aa197 | 19 | Reads the tree information given by <tree-ish> into the index, |
c1bdacf9 | 20 | but does not actually *update* any of the files it "caches". (see: |
5162e697 | 21 | linkgit:git-checkout-index[1]) |
2cf565c5 | 22 | |
5f3aa197 | 23 | Optionally, it can merge a tree into the index, perform a |
61f693bd JL |
24 | fast-forward (i.e. 2-way) merge, or a 3-way merge, with the `-m` |
25 | flag. When used with `-m`, the `-u` flag causes it to also update | |
ccef66b5 | 26 | the files in the work tree with the result of the merge. |
2cf565c5 | 27 | |
0b444cdb TR |
28 | Trivial merges are done by 'git read-tree' itself. Only conflicting paths |
29 | will be in unmerged state when 'git read-tree' returns. | |
2cf565c5 DG |
30 | |
31 | OPTIONS | |
32 | ------- | |
33 | -m:: | |
3f41f5a9 | 34 | Perform a merge, not just a read. The command will |
35 | refuse to run if your index file has unmerged entries, | |
36 | indicating that you have not finished previous merge you | |
37 | started. | |
ccef66b5 | 38 | |
2db0bfbc | 39 | --reset:: |
3f41f5a9 | 40 | Same as -m, except that unmerged entries are discarded |
41 | instead of failing. | |
2db0bfbc | 42 | |
ccef66b5 JH |
43 | -u:: |
44 | After a successful merge, update the files in the work | |
45 | tree with the result of the merge. | |
2cf565c5 | 46 | |
f318dd22 JH |
47 | -i:: |
48 | Usually a merge requires the index file as well as the | |
49 | files in the working tree are up to date with the | |
50 | current head commit, in order not to lose local | |
51 | changes. This flag disables the check with the working | |
52 | tree and is meant to be used when creating a merge of | |
53 | trees that are not directly related to the current | |
54 | working tree status into a temporary index file. | |
55 | ||
22e801f2 MV |
56 | -v:: |
57 | Show the progress of checking files out. | |
58 | ||
6da08783 | 59 | --trivial:: |
0b444cdb | 60 | Restrict three-way merge by 'git read-tree' to happen |
6da08783 JN |
61 | only if there is no file-level merging required, instead |
62 | of resolving merge for trivial cases and leaving | |
63 | conflicting files unresolved in the index. | |
64 | ||
afaa8d66 | 65 | --aggressive:: |
0b444cdb | 66 | Usually a three-way merge by 'git read-tree' resolves |
afaa8d66 JH |
67 | the merge for really trivial cases and leaves other |
68 | cases unresolved in the index, so that Porcelains can | |
69 | implement different merge policies. This flag makes the | |
70 | command to resolve a few more cases internally: | |
71 | + | |
72 | * when one side removes a path and the other side leaves the path | |
73 | unmodified. The resolution is to remove that path. | |
74 | * when both sides remove a path. The resolution is to remove that path. | |
75 | * when both sides adds a path identically. The resolution | |
76 | is to add that path. | |
77 | ||
f4c6f2d3 JH |
78 | --prefix=<prefix>/:: |
79 | Keep the current index contents, and read the contents | |
80 | of named tree-ish under directory at `<prefix>`. The | |
81 | original index file cannot have anything at the path | |
82 | `<prefix>` itself, and have nothing in `<prefix>/` | |
83 | directory. Note that the `<prefix>/` value must end | |
84 | with a slash. | |
85 | ||
22f741da JH |
86 | --exclude-per-directory=<gitignore>:: |
87 | When running the command with `-u` and `-m` options, the | |
88 | merge result may need to overwrite paths that are not | |
89 | tracked in the current branch. The command usually | |
90 | refuses to proceed with the merge to avoid losing such a | |
91 | path. However this safety valve sometimes gets in the | |
92 | way. For example, it often happens that the other | |
93 | branch added a file that used to be a generated file in | |
94 | your branch, and the safety valve triggers when you try | |
95 | to switch to that branch after you ran `make` but before | |
96 | running `make clean` to remove the generated file. This | |
97 | option tells the command to read per-directory exclude | |
98 | file (usually '.gitignore') and allows such an untracked | |
99 | but explicitly ignored file to be overwritten. | |
f4c6f2d3 | 100 | |
5e7f56ac JH |
101 | --index-output=<file>:: |
102 | Instead of writing the results out to `$GIT_INDEX_FILE`, | |
103 | write the resulting index in the named file. While the | |
104 | command is operating, the original index file is locked | |
105 | with the same mechanism as usual. The file must allow | |
106 | to be rename(2)ed into from a temporary file that is | |
107 | created next to the usual index file; typically this | |
108 | means it needs to be on the same filesystem as the index | |
109 | file itself, and you need write permission to the | |
110 | directories the index file and index output file are | |
111 | located in. | |
112 | ||
a5d07d0f NTND |
113 | --no-sparse-checkout:: |
114 | Disable sparse checkout support even if `core.sparseCheckout` | |
115 | is true. | |
116 | ||
fb1bb965 JK |
117 | --empty:: |
118 | Instead of reading tree object(s) into the index, just empty | |
119 | it. | |
120 | ||
2cf565c5 DG |
121 | <tree-ish#>:: |
122 | The id of the tree object(s) to be read/merged. | |
123 | ||
124 | ||
125 | Merging | |
126 | ------- | |
0b444cdb | 127 | If `-m` is specified, 'git read-tree' can perform 3 kinds of |
ccef66b5 JH |
128 | merge, a single tree merge if only 1 tree is given, a |
129 | fast-forward merge with 2 trees, or a 3-way merge if 3 trees are | |
2cf565c5 DG |
130 | provided. |
131 | ||
ccef66b5 | 132 | |
2cf565c5 DG |
133 | Single Tree Merge |
134 | ~~~~~~~~~~~~~~~~~ | |
0b444cdb | 135 | If only 1 tree is specified, 'git read-tree' operates as if the user did not |
61f693bd | 136 | specify `-m`, except that if the original index has an entry for a |
73252839 | 137 | given pathname, and the contents of the path match with the tree |
5f3aa197 LS |
138 | being read, the stat info from the index is used. (In other words, the |
139 | index's stat()s take precedence over the merged tree's). | |
2cf565c5 | 140 | |
b1889c36 | 141 | That means that if you do a `git read-tree -m <newtree>` followed by a |
0b444cdb | 142 | `git checkout-index -f -u -a`, the 'git checkout-index' only checks out |
2cf565c5 DG |
143 | the stuff that really changed. |
144 | ||
0b444cdb TR |
145 | This is used to avoid unnecessary false hits when 'git diff-files' is |
146 | run after 'git read-tree'. | |
2cf565c5 | 147 | |
c8596009 JH |
148 | |
149 | Two Tree Merge | |
150 | ~~~~~~~~~~~~~~ | |
151 | ||
b1889c36 | 152 | Typically, this is invoked as `git read-tree -m $H $M`, where $H |
c8596009 JH |
153 | is the head commit of the current repository, and $M is the head |
154 | of a foreign tree, which is simply ahead of $H (i.e. we are in a | |
a75d7b54 | 155 | fast-forward situation). |
c8596009 | 156 | |
0b444cdb | 157 | When two trees are specified, the user is telling 'git read-tree' |
c8596009 JH |
158 | the following: |
159 | ||
df8baa42 | 160 | 1. The current index and work tree is derived from $H, but |
73252839 | 161 | the user may have local changes in them since $H. |
c8596009 | 162 | |
df8baa42 | 163 | 2. The user wants to fast-forward to $M. |
c8596009 | 164 | |
b1889c36 | 165 | In this case, the `git read-tree -m $H $M` command makes sure |
c8596009 | 166 | that no local change is lost as the result of this "merge". |
73252839 MG |
167 | Here are the "carry forward" rules, where "I" denotes the index, |
168 | "clean" means that index and work tree coincide, and "exists"/"nothing" | |
169 | refer to the presence of a path in the specified commit: | |
c8596009 | 170 | |
73252839 | 171 | I H M Result |
c8596009 | 172 | ------------------------------------------------------- |
71928f7f MG |
173 | 0 nothing nothing nothing (does not happen) |
174 | 1 nothing nothing exists use M | |
175 | 2 nothing exists nothing remove path from index | |
73252839 | 176 | 3 nothing exists exists, use M if "initial checkout", |
55218834 | 177 | H == M keep index otherwise |
73252839 | 178 | exists, fail |
55218834 | 179 | H != M |
c8596009 JH |
180 | |
181 | clean I==H I==M | |
182 | ------------------ | |
71928f7f MG |
183 | 4 yes N/A N/A nothing nothing keep index |
184 | 5 no N/A N/A nothing nothing keep index | |
c8596009 | 185 | |
71928f7f MG |
186 | 6 yes N/A yes nothing exists keep index |
187 | 7 no N/A yes nothing exists keep index | |
188 | 8 yes N/A no nothing exists fail | |
189 | 9 no N/A no nothing exists fail | |
c8596009 | 190 | |
5f3aa197 | 191 | 10 yes yes N/A exists nothing remove path from index |
c8596009 JH |
192 | 11 no yes N/A exists nothing fail |
193 | 12 yes no N/A exists nothing fail | |
194 | 13 no no N/A exists nothing fail | |
195 | ||
73252839 | 196 | clean (H==M) |
c8596009 JH |
197 | ------ |
198 | 14 yes exists exists keep index | |
199 | 15 no exists exists keep index | |
200 | ||
201 | clean I==H I==M (H!=M) | |
202 | ------------------ | |
203 | 16 yes no no exists exists fail | |
204 | 17 no no no exists exists fail | |
205 | 18 yes no yes exists exists keep index | |
206 | 19 no no yes exists exists keep index | |
207 | 20 yes yes no exists exists use M | |
208 | 21 no yes no exists exists fail | |
209 | ||
5f3aa197 | 210 | In all "keep index" cases, the index entry stays as in the |
73252839 | 211 | original index file. If the entry is not up to date, |
0b444cdb | 212 | 'git read-tree' keeps the copy in the work tree intact when |
c8596009 JH |
213 | operating under the -u flag. |
214 | ||
0b444cdb | 215 | When this form of 'git read-tree' returns successfully, you can |
73252839 | 216 | see which of the "local changes" that you made were carried forward by running |
b1889c36 | 217 | `git diff-index --cached $M`. Note that this does not |
73252839 | 218 | necessarily match what `git diff-index --cached $H` would have |
c8596009 JH |
219 | produced before such a two tree merge. This is because of cases |
220 | 18 and 19 --- if you already had the changes in $M (e.g. maybe | |
b1889c36 | 221 | you picked it up via e-mail in a patch form), `git diff-index |
61f693bd | 222 | --cached $H` would have told you about the change before this |
b1889c36 | 223 | merge, but it would not show in `git diff-index --cached $M` |
73252839 | 224 | output after the two-tree merge. |
c8596009 | 225 | |
73252839 | 226 | Case 3 is slightly tricky and needs explanation. The result from this |
55218834 | 227 | rule logically should be to remove the path if the user staged the removal |
79fd4cc7 | 228 | of the path and then switching to a new branch. That however will prevent |
55218834 | 229 | the initial checkout from happening, so the rule is modified to use M (new |
73252839 | 230 | tree) only when the content of the index is empty. Otherwise the removal |
55218834 | 231 | of the path is kept as long as $H and $M are the same. |
c8596009 | 232 | |
2cf565c5 DG |
233 | 3-Way Merge |
234 | ~~~~~~~~~~~ | |
235 | Each "index" entry has two bits worth of "stage" state. stage 0 is the | |
236 | normal one, and is the only one you'd see in any kind of normal use. | |
237 | ||
0b444cdb | 238 | However, when you do 'git read-tree' with three trees, the "stage" |
2cf565c5 DG |
239 | starts out at 1. |
240 | ||
241 | This means that you can do | |
242 | ||
61f693bd | 243 | ---------------- |
b1889c36 | 244 | $ git read-tree -m <tree1> <tree2> <tree3> |
61f693bd | 245 | ---------------- |
2cf565c5 DG |
246 | |
247 | and you will end up with an index with all of the <tree1> entries in | |
248 | "stage1", all of the <tree2> entries in "stage2" and all of the | |
bb6d7b89 JH |
249 | <tree3> entries in "stage3". When performing a merge of another |
250 | branch into the current branch, we use the common ancestor tree | |
251 | as <tree1>, the current branch head as <tree2>, and the other | |
252 | branch head as <tree3>. | |
2cf565c5 | 253 | |
0b444cdb | 254 | Furthermore, 'git read-tree' has special-case logic that says: if you see |
2cf565c5 DG |
255 | a file that matches in all respects in the following states, it |
256 | "collapses" back to "stage0": | |
257 | ||
258 | - stage 2 and 3 are the same; take one or the other (it makes no | |
bb6d7b89 JH |
259 | difference - the same work has been done on our branch in |
260 | stage 2 and their branch in stage 3) | |
2cf565c5 DG |
261 | |
262 | - stage 1 and stage 2 are the same and stage 3 is different; take | |
bb6d7b89 JH |
263 | stage 3 (our branch in stage 2 did not do anything since the |
264 | ancestor in stage 1 while their branch in stage 3 worked on | |
265 | it) | |
2cf565c5 DG |
266 | |
267 | - stage 1 and stage 3 are the same and stage 2 is different take | |
bb6d7b89 | 268 | stage 2 (we did something while they did nothing) |
2cf565c5 | 269 | |
0b444cdb | 270 | The 'git write-tree' command refuses to write a nonsensical tree, and it |
2cf565c5 DG |
271 | will complain about unmerged entries if it sees a single entry that is not |
272 | stage 0. | |
273 | ||
abda1ef5 | 274 | OK, this all sounds like a collection of totally nonsensical rules, |
2cf565c5 DG |
275 | but it's actually exactly what you want in order to do a fast |
276 | merge. The different stages represent the "result tree" (stage 0, aka | |
277 | "merged"), the original tree (stage 1, aka "orig"), and the two trees | |
278 | you are trying to merge (stage 2 and 3 respectively). | |
279 | ||
ccef66b5 JH |
280 | The order of stages 1, 2 and 3 (hence the order of three |
281 | <tree-ish> command line arguments) are significant when you | |
282 | start a 3-way merge with an index file that is already | |
283 | populated. Here is an outline of how the algorithm works: | |
2cf565c5 DG |
284 | |
285 | - if a file exists in identical format in all three trees, it will | |
0b444cdb | 286 | automatically collapse to "merged" state by 'git read-tree'. |
2cf565c5 DG |
287 | |
288 | - a file that has _any_ difference what-so-ever in the three trees | |
2c6e4771 | 289 | will stay as separate entries in the index. It's up to "porcelain |
2cf565c5 | 290 | policy" to determine how to remove the non-0 stages, and insert a |
ccef66b5 | 291 | merged version. |
2cf565c5 DG |
292 | |
293 | - the index file saves and restores with all this information, so you | |
294 | can merge things incrementally, but as long as it has entries in | |
abda1ef5 | 295 | stages 1/2/3 (i.e., "unmerged entries") you can't write the result. So |
2cf565c5 DG |
296 | now the merge algorithm ends up being really simple: |
297 | ||
298 | * you walk the index in order, and ignore all entries of stage 0, | |
299 | since they've already been done. | |
300 | ||
301 | * if you find a "stage1", but no matching "stage2" or "stage3", you | |
302 | know it's been removed from both trees (it only existed in the | |
303 | original tree), and you remove that entry. | |
304 | ||
305 | * if you find a matching "stage2" and "stage3" tree, you remove one | |
306 | of them, and turn the other into a "stage0" entry. Remove any | |
307 | matching "stage1" entry if it exists too. .. all the normal | |
308 | trivial rules .. | |
309 | ||
0b444cdb TR |
310 | You would normally use 'git merge-index' with supplied |
311 | 'git merge-one-file' to do this last step. The script updates | |
bb6d7b89 JH |
312 | the files in the working tree as it merges each path and at the |
313 | end of a successful merge. | |
ccef66b5 JH |
314 | |
315 | When you start a 3-way merge with an index file that is already | |
316 | populated, it is assumed that it represents the state of the | |
317 | files in your work tree, and you can even have files with | |
318 | changes unrecorded in the index file. It is further assumed | |
319 | that this state is "derived" from the stage 2 tree. The 3-way | |
320 | merge refuses to run if it finds an entry in the original index | |
321 | file that does not match stage 2. | |
322 | ||
323 | This is done to prevent you from losing your work-in-progress | |
bb6d7b89 JH |
324 | changes, and mixing your random changes in an unrelated merge |
325 | commit. To illustrate, suppose you start from what has been | |
37425065 | 326 | committed last to your repository: |
ccef66b5 | 327 | |
61f693bd | 328 | ---------------- |
b1889c36 JN |
329 | $ JC=`git rev-parse --verify "HEAD^0"` |
330 | $ git checkout-index -f -u -a $JC | |
61f693bd | 331 | ---------------- |
ccef66b5 | 332 | |
0b444cdb | 333 | You do random edits, without running 'git update-index'. And then |
ccef66b5 JH |
334 | you notice that the tip of your "upstream" tree has advanced |
335 | since you pulled from him: | |
336 | ||
61f693bd | 337 | ---------------- |
b1889c36 | 338 | $ git fetch git://.... linus |
bb6d7b89 | 339 | $ LT=`cat .git/FETCH_HEAD` |
61f693bd | 340 | ---------------- |
ccef66b5 JH |
341 | |
342 | Your work tree is still based on your HEAD ($JC), but you have | |
343 | some edits since. Three-way merge makes sure that you have not | |
5f3aa197 | 344 | added or modified index entries since $JC, and if you haven't, |
ccef66b5 JH |
345 | then does the right thing. So with the following sequence: |
346 | ||
61f693bd | 347 | ---------------- |
b1889c36 JN |
348 | $ git read-tree -m -u `git merge-base $JC $LT` $JC $LT |
349 | $ git merge-index git-merge-one-file -a | |
61f693bd | 350 | $ echo "Merge with Linus" | \ |
b1889c36 | 351 | git commit-tree `git write-tree` -p $JC -p $LT |
61f693bd | 352 | ---------------- |
ccef66b5 | 353 | |
61f693bd | 354 | what you would commit is a pure merge between $JC and $LT without |
ccef66b5 JH |
355 | your work-in-progress changes, and your work tree would be |
356 | updated to the result of the merge. | |
357 | ||
bb6d7b89 | 358 | However, if you have local changes in the working tree that |
0b444cdb | 359 | would be overwritten by this merge, 'git read-tree' will refuse |
bb6d7b89 JH |
360 | to run to prevent your changes from being lost. |
361 | ||
362 | In other words, there is no need to worry about what exists only | |
363 | in the working tree. When you have local changes in a part of | |
364 | the project that is not involved in the merge, your changes do | |
365 | not interfere with the merge, and are kept intact. When they | |
0b444cdb | 366 | *do* interfere, the merge does not even start ('git read-tree' |
bb6d7b89 JH |
367 | complains loudly and fails without modifying anything). In such |
368 | a case, you can simply continue doing what you were in the | |
369 | middle of doing, and when your working tree is ready (i.e. you | |
370 | have finished your work-in-progress), attempt the merge again. | |
371 | ||
2cf565c5 | 372 | |
ed5336a7 NTND |
373 | Sparse checkout |
374 | --------------- | |
375 | ||
376 | "Sparse checkout" allows to sparsely populate working directory. | |
377 | It uses skip-worktree bit (see linkgit:git-update-index[1]) to tell | |
378 | Git whether a file on working directory is worth looking at. | |
379 | ||
380 | "git read-tree" and other merge-based commands ("git merge", "git | |
381 | checkout"...) can help maintaining skip-worktree bitmap and working | |
382 | directory update. `$GIT_DIR/info/sparse-checkout` is used to | |
383 | define the skip-worktree reference bitmap. When "git read-tree" needs | |
384 | to update working directory, it will reset skip-worktree bit in index | |
385 | based on this file, which uses the same syntax as .gitignore files. | |
386 | If an entry matches a pattern in this file, skip-worktree will be | |
387 | set on that entry. Otherwise, skip-worktree will be unset. | |
388 | ||
389 | Then it compares the new skip-worktree value with the previous one. If | |
390 | skip-worktree turns from unset to set, it will add the corresponding | |
391 | file back. If it turns from set to unset, that file will be removed. | |
392 | ||
393 | While `$GIT_DIR/info/sparse-checkout` is usually used to specify what | |
394 | files are in. You can also specify what files are _not_ in, using | |
395 | negate patterns. For example, to remove file "unwanted": | |
396 | ||
397 | ---------------- | |
398 | * | |
399 | !unwanted | |
400 | ---------------- | |
401 | ||
402 | Another tricky thing is fully repopulating working directory when you | |
403 | no longer want sparse checkout. You cannot just disable "sparse | |
404 | checkout" because skip-worktree are still in the index and you working | |
405 | directory is still sparsely populated. You should re-populate working | |
406 | directory with the `$GIT_DIR/info/sparse-checkout` file content as | |
407 | follows: | |
408 | ||
409 | ---------------- | |
410 | * | |
411 | ---------------- | |
412 | ||
413 | Then you can disable sparse checkout. Sparse checkout support in "git | |
08aefc9e NTND |
414 | read-tree" and similar commands is disabled by default. You need to |
415 | turn `core.sparseCheckout` on in order to have sparse checkout | |
416 | support. | |
ed5336a7 NTND |
417 | |
418 | ||
cdad3c54 NTND |
419 | BUGS |
420 | ---- | |
421 | In order to match a directory with $GIT_DIR/info/sparse-checkout, | |
422 | trailing slash must be used. The form without trailing slash, while | |
423 | works with .gitignore, does not work with sparse checkout. | |
424 | ||
425 | ||
56ae8df5 | 426 | SEE ALSO |
c1bdacf9 | 427 | -------- |
5162e697 DM |
428 | linkgit:git-write-tree[1]; linkgit:git-ls-files[1]; |
429 | linkgit:gitignore[5] | |
2cf565c5 DG |
430 | |
431 | ||
432 | Author | |
433 | ------ | |
434 | Written by Linus Torvalds <torvalds@osdl.org> | |
435 | ||
436 | Documentation | |
437 | -------------- | |
438 | Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>. | |
439 | ||
440 | GIT | |
441 | --- | |
9e1f0a85 | 442 | Part of the linkgit:git[1] suite |