Make git-add behave more sensibly in a case-insensitive environment
[git/git.git] / Documentation / git-filter-branch.txt
1 git-filter-branch(1)
2 ====================
3
4 NAME
5 ----
6 git-filter-branch - Rewrite branches
7
8 SYNOPSIS
9 --------
10 [verse]
11 'git-filter-branch' [--env-filter <command>] [--tree-filter <command>]
12 [--index-filter <command>] [--parent-filter <command>]
13 [--msg-filter <command>] [--commit-filter <command>]
14 [--tag-name-filter <command>] [--subdirectory-filter <directory>]
15 [--original <namespace>] [-d <directory>] [-f | --force]
16 [<rev-list options>...]
17
18 DESCRIPTION
19 -----------
20 Lets you rewrite git revision history by rewriting the branches mentioned
21 in the <rev-list options>, applying custom filters on each revision.
22 Those filters can modify each tree (e.g. removing a file or running
23 a perl rewrite on all files) or information about each commit.
24 Otherwise, all information (including original commit times or merge
25 information) will be preserved.
26
27 The command will only rewrite the _positive_ refs mentioned in the
28 command line (e.g. if you pass 'a..b', only 'b' will be rewritten).
29 If you specify no filters, the commits will be recommitted without any
30 changes, which would normally have no effect. Nevertheless, this may be
31 useful in the future for compensating for some git bugs or such,
32 therefore such a usage is permitted.
33
34 *WARNING*! The rewritten history will have different object names for all
35 the objects and will not converge with the original branch. You will not
36 be able to easily push and distribute the rewritten branch on top of the
37 original branch. Please do not use this command if you do not know the
38 full implications, and avoid using it anyway, if a simple single commit
39 would suffice to fix your problem.
40
41 Always verify that the rewritten version is correct: The original refs,
42 if different from the rewritten ones, will be stored in the namespace
43 'refs/original/'.
44
45 Note that since this operation is very I/O expensive, it might
46 be a good idea to redirect the temporary directory off-disk with the
47 '-d' option, e.g. on tmpfs. Reportedly the speedup is very noticeable.
48
49
50 Filters
51 ~~~~~~~
52
53 The filters are applied in the order as listed below. The <command>
54 argument is always evaluated in the shell context using the 'eval' command
55 (with the notable exception of the commit filter, for technical reasons).
56 Prior to that, the $GIT_COMMIT environment variable will be set to contain
57 the id of the commit being rewritten. Also, GIT_AUTHOR_NAME,
58 GIT_AUTHOR_EMAIL, GIT_AUTHOR_DATE, GIT_COMMITTER_NAME, GIT_COMMITTER_EMAIL,
59 and GIT_COMMITTER_DATE are set according to the current commit. The values
60 of these variables after the filters have run, are used for the new commit.
61 If any evaluation of <command> returns a non-zero exit status, the whole
62 operation will be aborted.
63
64 A 'map' function is available that takes an "original sha1 id" argument
65 and outputs a "rewritten sha1 id" if the commit has been already
66 rewritten, and "original sha1 id" otherwise; the 'map' function can
67 return several ids on separate lines if your commit filter emitted
68 multiple commits.
69
70
71 OPTIONS
72 -------
73
74 --env-filter <command>::
75 This filter may be used if you only need to modify the environment
76 in which the commit will be performed. Specifically, you might
77 want to rewrite the author/committer name/email/time environment
78 variables (see linkgit:git-commit[1] for details). Do not forget
79 to re-export the variables.
80
81 --tree-filter <command>::
82 This is the filter for rewriting the tree and its contents.
83 The argument is evaluated in shell with the working
84 directory set to the root of the checked out tree. The new tree
85 is then used as-is (new files are auto-added, disappeared files
86 are auto-removed - neither .gitignore files nor any other ignore
87 rules *HAVE ANY EFFECT*!).
88
89 --index-filter <command>::
90 This is the filter for rewriting the index. It is similar to the
91 tree filter but does not check out the tree, which makes it much
92 faster. For hairy cases, see linkgit:git-update-index[1].
93
94 --parent-filter <command>::
95 This is the filter for rewriting the commit's parent list.
96 It will receive the parent string on stdin and shall output
97 the new parent string on stdout. The parent string is in
98 a format accepted by linkgit:git-commit-tree[1]: empty for
99 the initial commit, "-p parent" for a normal commit and
100 "-p parent1 -p parent2 -p parent3 ..." for a merge commit.
101
102 --msg-filter <command>::
103 This is the filter for rewriting the commit messages.
104 The argument is evaluated in the shell with the original
105 commit message on standard input; its standard output is
106 used as the new commit message.
107
108 --commit-filter <command>::
109 This is the filter for performing the commit.
110 If this filter is specified, it will be called instead of the
111 linkgit:git-commit-tree[1] command, with arguments of the form
112 "<TREE_ID> [-p <PARENT_COMMIT_ID>]..." and the log message on
113 stdin. The commit id is expected on stdout.
114 +
115 As a special extension, the commit filter may emit multiple
116 commit ids; in that case, ancestors of the original commit will
117 have all of them as parents.
118 +
119 You can use the 'map' convenience function in this filter, and other
120 convenience functions, too. For example, calling 'skip_commit "$@"'
121 will leave out the current commit (but not its changes! If you want
122 that, use linkgit:git-rebase[1] instead).
123
124 --tag-name-filter <command>::
125 This is the filter for rewriting tag names. When passed,
126 it will be called for every tag ref that points to a rewritten
127 object (or to a tag object which points to a rewritten object).
128 The original tag name is passed via standard input, and the new
129 tag name is expected on standard output.
130 +
131 The original tags are not deleted, but can be overwritten;
132 use "--tag-name-filter cat" to simply update the tags. In this
133 case, be very careful and make sure you have the old tags
134 backed up in case the conversion has run afoul.
135 +
136 Note that there is currently no support for proper rewriting of
137 tag objects; in layman terms, if the tag has a message or signature
138 attached, the rewritten tag won't have it. Sorry. (It is by
139 definition impossible to preserve signatures at any rate.)
140
141 --subdirectory-filter <directory>::
142 Only look at the history which touches the given subdirectory.
143 The result will contain that directory (and only that) as its
144 project root.
145
146 --original <namespace>::
147 Use this option to set the namespace where the original commits
148 will be stored. The default value is 'refs/original'.
149
150 -d <directory>::
151 Use this option to set the path to the temporary directory used for
152 rewriting. When applying a tree filter, the command needs to
153 temporarily check out the tree to some directory, which may consume
154 considerable space in case of large projects. By default it
155 does this in the '.git-rewrite/' directory but you can override
156 that choice by this parameter.
157
158 -f|--force::
159 `git filter-branch` refuses to start with an existing temporary
160 directory or when there are already refs starting with
161 'refs/original/', unless forced.
162
163 <rev-list-options>::
164 When options are given after the new branch name, they will
165 be passed to linkgit:git-rev-list[1]. Only commits in the resulting
166 output will be filtered, although the filtered commits can still
167 reference parents which are outside of that set.
168
169
170 Examples
171 --------
172
173 Suppose you want to remove a file (containing confidential information
174 or copyright violation) from all commits:
175
176 -------------------------------------------------------
177 git filter-branch --tree-filter 'rm filename' HEAD
178 -------------------------------------------------------
179
180 A significantly faster version:
181
182 --------------------------------------------------------------------------
183 git filter-branch --index-filter 'git update-index --remove filename' HEAD
184 --------------------------------------------------------------------------
185
186 Now, you will get the rewritten history saved in HEAD.
187
188 To set a commit (which typically is at the tip of another
189 history) to be the parent of the current initial commit, in
190 order to paste the other history behind the current history:
191
192 -------------------------------------------------------------------
193 git filter-branch --parent-filter 'sed "s/^\$/-p <graft-id>/"' HEAD
194 -------------------------------------------------------------------
195
196 (if the parent string is empty - which happens when we are dealing with
197 the initial commit - add graftcommit as a parent). Note that this assumes
198 history with a single root (that is, no merge without common ancestors
199 happened). If this is not the case, use:
200
201 --------------------------------------------------------------------------
202 git filter-branch --parent-filter \
203 'test $GIT_COMMIT = <commit-id> && echo "-p <graft-id>" || cat' HEAD
204 --------------------------------------------------------------------------
205
206 or even simpler:
207
208 -----------------------------------------------
209 echo "$commit-id $graft-id" >> .git/info/grafts
210 git filter-branch $graft-id..HEAD
211 -----------------------------------------------
212
213 To remove commits authored by "Darl McBribe" from the history:
214
215 ------------------------------------------------------------------------------
216 git filter-branch --commit-filter '
217 if [ "$GIT_AUTHOR_NAME" = "Darl McBribe" ];
218 then
219 skip_commit "$@";
220 else
221 git commit-tree "$@";
222 fi' HEAD
223 ------------------------------------------------------------------------------
224
225 The function 'skip_commit' is defined as follows:
226
227 --------------------------
228 skip_commit()
229 {
230 shift;
231 while [ -n "$1" ];
232 do
233 shift;
234 map "$1";
235 shift;
236 done;
237 }
238 --------------------------
239
240 The shift magic first throws away the tree id and then the -p
241 parameters. Note that this handles merges properly! In case Darl
242 committed a merge between P1 and P2, it will be propagated properly
243 and all children of the merge will become merge commits with P1,P2
244 as their parents instead of the merge commit.
245
246 You can rewrite the commit log messages using `--message-filter`. For
247 example, `git-svn-id` strings in a repository created by `git-svn` can
248 be removed this way:
249
250 -------------------------------------------------------
251 git filter-branch --message-filter '
252 sed -e "/^git-svn-id:/d"
253 '
254 -------------------------------------------------------
255
256 To restrict rewriting to only part of the history, specify a revision
257 range in addition to the new branch name. The new branch name will
258 point to the top-most revision that a 'git rev-list' of this range
259 will print.
260
261 *NOTE* the changes introduced by the commits, and which are not reverted
262 by subsequent commits, will still be in the rewritten branch. If you want
263 to throw out _changes_ together with the commits, you should use the
264 interactive mode of linkgit:git-rebase[1].
265
266
267 Consider this history:
268
269 ------------------
270 D--E--F--G--H
271 / /
272 A--B-----C
273 ------------------
274
275 To rewrite only commits D,E,F,G,H, but leave A, B and C alone, use:
276
277 --------------------------------
278 git filter-branch ... C..H
279 --------------------------------
280
281 To rewrite commits E,F,G,H, use one of these:
282
283 ----------------------------------------
284 git filter-branch ... C..H --not D
285 git filter-branch ... D..H --not C
286 ----------------------------------------
287
288 To move the whole tree into a subdirectory, or remove it from there:
289
290 ---------------------------------------------------------------
291 git filter-branch --index-filter \
292 'git ls-files -s | sed "s-\t-&newsubdir/-" |
293 GIT_INDEX_FILE=$GIT_INDEX_FILE.new \
294 git update-index --index-info &&
295 mv $GIT_INDEX_FILE.new $GIT_INDEX_FILE' HEAD
296 ---------------------------------------------------------------
297
298
299 Author
300 ------
301 Written by Petr "Pasky" Baudis <pasky@suse.cz>,
302 and the git list <git@vger.kernel.org>
303
304 Documentation
305 --------------
306 Documentation by Petr Baudis and the git list.
307
308 GIT
309 ---
310 Part of the linkgit:git[7] suite