pre-rebase hook update
[git/git.git] / templates / hooks--pre-rebase
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1#!/bin/sh
2#
ba2d0f4f 3# Copyright (c) 2006, 2008 Junio C Hamano
9a111c91 4#
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5# The "pre-rebase" hook is run just before "git-rebase" starts doing
6# its job, and can prevent the command from running by exiting with
7# non-zero status.
8#
9# The hook is called with the following parameters:
10#
11# $1 -- the upstream the series was forked from.
12# $2 -- the branch being rebased (or empty when rebasing the current branch).
13#
14# This sample shows how to prevent topic branches that are already
15# merged to 'next' branch from getting rebased, because allowing it
16# would result in rebasing already published history.
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17
18publish=next
19basebranch="$1"
20if test "$#" = 2
21then
22 topic="refs/heads/$2"
23else
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24 topic=`git symbolic-ref HEAD` ||
25 exit 0 ;# we do not interrupt rebasing detached HEAD
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26fi
27
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28case "$topic" in
29refs/heads/??/*)
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30 ;;
31*)
32 exit 0 ;# we do not interrupt others.
33 ;;
34esac
35
36# Now we are dealing with a topic branch being rebased
37# on top of master. Is it OK to rebase it?
38
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39# Does the topic really exist?
40git show-ref -q "$topic" || {
41 echo >&2 "No such branch $topic"
42 exit 1
43}
44
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45# Is topic fully merged to master?
46not_in_master=`git-rev-list --pretty=oneline ^master "$topic"`
47if test -z "$not_in_master"
48then
49 echo >&2 "$topic is fully merged to master; better remove it."
50 exit 1 ;# we could allow it, but there is no point.
51fi
52
53# Is topic ever merged to next? If so you should not be rebasing it.
54only_next_1=`git-rev-list ^master "^$topic" ${publish} | sort`
55only_next_2=`git-rev-list ^master ${publish} | sort`
56if test "$only_next_1" = "$only_next_2"
57then
58 not_in_topic=`git-rev-list "^$topic" master`
59 if test -z "$not_in_topic"
60 then
61 echo >&2 "$topic is already up-to-date with master"
62 exit 1 ;# we could allow it, but there is no point.
63 else
64 exit 0
65 fi
66else
67 not_in_next=`git-rev-list --pretty=oneline ^${publish} "$topic"`
68 perl -e '
69 my $topic = $ARGV[0];
70 my $msg = "* $topic has commits already merged to public branch:\n";
71 my (%not_in_next) = map {
72 /^([0-9a-f]+) /;
73 ($1 => 1);
74 } split(/\n/, $ARGV[1]);
75 for my $elem (map {
76 /^([0-9a-f]+) (.*)$/;
77 [$1 => $2];
78 } split(/\n/, $ARGV[2])) {
79 if (!exists $not_in_next{$elem->[0]}) {
80 if ($msg) {
81 print STDERR $msg;
82 undef $msg;
83 }
84 print STDERR " $elem->[1]\n";
85 }
86 }
87 ' "$topic" "$not_in_next" "$not_in_master"
88 exit 1
89fi
90
91exit 0
92
93################################################################
94
95This sample hook safeguards topic branches that have been
96published from being rewound.
97
98The workflow assumed here is:
99
100 * Once a topic branch forks from "master", "master" is never
101 merged into it again (either directly or indirectly).
102
103 * Once a topic branch is fully cooked and merged into "master",
104 it is deleted. If you need to build on top of it to correct
105 earlier mistakes, a new topic branch is created by forking at
106 the tip of the "master". This is not strictly necessary, but
107 it makes it easier to keep your history simple.
108
109 * Whenever you need to test or publish your changes to topic
110 branches, merge them into "next" branch.
111
112The script, being an example, hardcodes the publish branch name
113to be "next", but it is trivial to make it configurable via
114$GIT_DIR/config mechanism.
115
116With this workflow, you would want to know:
117
118(1) ... if a topic branch has ever been merged to "next". Young
119 topic branches can have stupid mistakes you would rather
120 clean up before publishing, and things that have not been
121 merged into other branches can be easily rebased without
122 affecting other people. But once it is published, you would
123 not want to rewind it.
124
125(2) ... if a topic branch has been fully merged to "master".
126 Then you can delete it. More importantly, you should not
127 build on top of it -- other people may already want to
128 change things related to the topic as patches against your
129 "master", so if you need further changes, it is better to
130 fork the topic (perhaps with the same name) afresh from the
131 tip of "master".
132
133Let's look at this example:
134
135 o---o---o---o---o---o---o---o---o---o "next"
136 / / / /
137 / a---a---b A / /
138 / / / /
139 / / c---c---c---c B /
140 / / / \ /
141 / / / b---b C \ /
142 / / / / \ /
143 ---o---o---o---o---o---o---o---o---o---o---o "master"
144
145
146A, B and C are topic branches.
147
148 * A has one fix since it was merged up to "next".
149
150 * B has finished. It has been fully merged up to "master" and "next",
151 and is ready to be deleted.
152
153 * C has not merged to "next" at all.
154
155We would want to allow C to be rebased, refuse A, and encourage
156B to be deleted.
157
158To compute (1):
159
160 git-rev-list ^master ^topic next
161 git-rev-list ^master next
162
163 if these match, topic has not merged in next at all.
164
165To compute (2):
166
167 git-rev-list master..topic
168
169 if this is empty, it is fully merged to "master".