git-rerere.txt: grammatical fixups and cleanups
[git/git.git] / Documentation / git-rerere.txt
1 git-rerere(1)
2 =============
3
4 NAME
5 ----
6 git-rerere - Reuse recorded resolution of conflicted merges
7
8 SYNOPSIS
9 --------
10 'git rerere' ['clear'|'diff'|'status'|'gc']
11
12 DESCRIPTION
13 -----------
14
15 In a workflow employing relatively long lived topic branches,
16 the developer sometimes needs to resolve the same conflicts over
17 and over again until the topic branches are done (either merged
18 to the "release" branch, or sent out and accepted upstream).
19
20 This command assists the developer in this process by recording
21 conflicted automerge results and corresponding hand resolve results
22 on the initial manual merge, and applying previously recorded
23 hand resolutions to their corresponding automerge results.
24
25 [NOTE]
26 You need to set the configuration variable rerere.enabled to
27 enable this command.
28
29
30 COMMANDS
31 --------
32
33 Normally, 'git-rerere' is run without arguments or user-intervention.
34 However, it has several commands that allow it to interact with
35 its working state.
36
37 'clear'::
38
39 This resets the metadata used by rerere if a merge resolution is to be
40 aborted. Calling 'git-am [--skip|--abort]' or 'git-rebase [--skip|--abort]'
41 will automatically invoke this command.
42
43 'diff'::
44
45 This displays diffs for the current state of the resolution. It is
46 useful for tracking what has changed while the user is resolving
47 conflicts. Additional arguments are passed directly to the system
48 'diff' command installed in PATH.
49
50 'status'::
51
52 Like 'diff', but this only prints the filenames that will be tracked
53 for resolutions.
54
55 'gc'::
56
57 This prunes records of conflicted merges that
58 occurred a long time ago. By default, unresolved conflicts older
59 than 15 days and resolved conflicts older than 60
60 days are pruned. These defaults are controlled via the
61 `gc.rerereunresolved` and `gc.rerereresolved` configuration
62 variables respectively.
63
64
65 DISCUSSION
66 ----------
67
68 When your topic branch modifies an overlapping area that your
69 master branch (or upstream) touched since your topic branch
70 forked from it, you may want to test it with the latest master,
71 even before your topic branch is ready to be pushed upstream:
72
73 ------------
74 o---*---o topic
75 /
76 o---o---o---*---o---o master
77 ------------
78
79 For such a test, you need to merge master and topic somehow.
80 One way to do it is to pull master into the topic branch:
81
82 ------------
83 $ git checkout topic
84 $ git merge master
85
86 o---*---o---+ topic
87 / /
88 o---o---o---*---o---o master
89 ------------
90
91 The commits marked with `*` touch the same area in the same
92 file; you need to resolve the conflicts when creating the commit
93 marked with `{plus}`. Then you can test the result to make sure your
94 work-in-progress still works with what is in the latest master.
95
96 After this test merge, there are two ways to continue your work
97 on the topic. The easiest is to build on top of the test merge
98 commit `{plus}`, and when your work in the topic branch is finally
99 ready, pull the topic branch into master, and/or ask the
100 upstream to pull from you. By that time, however, the master or
101 the upstream might have been advanced since the test merge `{plus}`,
102 in which case the final commit graph would look like this:
103
104 ------------
105 $ git checkout topic
106 $ git merge master
107 $ ... work on both topic and master branches
108 $ git checkout master
109 $ git merge topic
110
111 o---*---o---+---o---o topic
112 / / \
113 o---o---o---*---o---o---o---o---+ master
114 ------------
115
116 When your topic branch is long-lived, however, your topic branch
117 would end up having many such "Merge from master" commits on it,
118 which would unnecessarily clutter the development history.
119 Readers of the Linux kernel mailing list may remember that Linus
120 complained about such too frequent test merges when a subsystem
121 maintainer asked to pull from a branch full of "useless merges".
122
123 As an alternative, to keep the topic branch clean of test
124 merges, you could blow away the test merge, and keep building on
125 top of the tip before the test merge:
126
127 ------------
128 $ git checkout topic
129 $ git merge master
130 $ git reset --hard HEAD^ ;# rewind the test merge
131 $ ... work on both topic and master branches
132 $ git checkout master
133 $ git merge topic
134
135 o---*---o-------o---o topic
136 / \
137 o---o---o---*---o---o---o---o---+ master
138 ------------
139
140 This would leave only one merge commit when your topic branch is
141 finally ready and merged into the master branch. This merge
142 would require you to resolve the conflict, introduced by the
143 commits marked with `*`. However, this conflict is often the
144 same conflict you resolved when you created the test merge you
145 blew away. 'git-rerere' helps you resolve this final
146 conflicted merge using the information from your earlier hand
147 resolve.
148
149 Running the 'git-rerere' command immediately after a conflicted
150 automerge records the conflicted working tree files, with the
151 usual conflict markers `<<<<<<<`, `=======`, and `>>>>>>>` in
152 them. Later, after you are done resolving the conflicts,
153 running 'git-rerere' again will record the resolved state of these
154 files. Suppose you did this when you created the test merge of
155 master into the topic branch.
156
157 Next time, after seeing the same conflicted automerge,
158 running 'git-rerere' will perform a three-way merge between the
159 earlier conflicted automerge, the earlier manual resolution, and
160 the current conflicted automerge.
161 If this three-way merge resolves cleanly, the result is written
162 out to your working tree file, so you do not have to manually
163 resolve it. Note that 'git-rerere' leaves the index file alone,
164 so you still need to do the final sanity checks with `git diff`
165 (or `git diff -c`) and 'git-add' when you are satisfied.
166
167 As a convenience measure, 'git-merge' automatically invokes
168 'git-rerere' upon exiting with a failed automerge and 'git-rerere'
169 records the hand resolve when it is a new conflict, or reuses the earlier hand
170 resolve when it is not. 'git-commit' also invokes 'git-rerere'
171 when committing a merge result. What this means is that you do
172 not have to do anything special yourself (besides enabling
173 the rerere.enabled config variable).
174
175 In our example, when you do the test merge, the manual
176 resolution is recorded, and it will be reused when you do the
177 actual merge later with the updated master and topic branch, as long
178 as the recorded resolution is still applicable.
179
180 The information 'git-rerere' records is also used when running
181 'git-rebase'. After blowing away the test merge and continuing
182 development on the topic branch:
183
184 ------------
185 o---*---o-------o---o topic
186 /
187 o---o---o---*---o---o---o---o master
188
189 $ git rebase master topic
190
191 o---*---o-------o---o topic
192 /
193 o---o---o---*---o---o---o---o master
194 ------------
195
196 you could run `git rebase master topic`, to bring yourself
197 up-to-date before your topic is ready to be sent upstream.
198 This would result in falling back to a three-way merge, and it
199 would conflict the same way as the test merge you resolved earlier.
200 'git-rerere' will be run by 'git-rebase' to help you resolve this
201 conflict.
202
203
204 Author
205 ------
206 Written by Junio C Hamano <gitster@pobox.com>
207
208 GIT
209 ---
210 Part of the linkgit:git[1] suite