build_scripts/.git/hooks/pre-rebase.sample

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1 | #!/bin/sh
2 | #
3 | # Copyright (c) 2006, 2008 Junio C Hamano
4 | #
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.
17 |
18 | publish=next
19 | basebranch="$1"
20 | if test "$#" = 2
21 | then
22 | topic="refs/heads/$2"
23 | else
24 | topic=`git symbolic-ref HEAD` ||
25 | exit 0 ;# we do not interrupt rebasing detached HEAD
26 | fi
27 |
28 | case "$topic" in
29 | refs/heads/??/*)
30 | ;;
31 | *)
32 | exit 0 ;# we do not interrupt others.
33 | ;;
34 | esac
35 |
36 | # Now we are dealing with a topic branch being rebased
37 | # on top of master. Is it OK to rebase it?
38 |
39 | # Does the topic really exist?
40 | git show-ref -q "$topic" || {
41 | echo >&2 "No such branch $topic"
42 | exit 1
43 | }
44 |
45 | # Is topic fully merged to master?
46 | not_in_master=`git rev-list --pretty=oneline ^master "$topic"`
47 | if test -z "$not_in_master"
48 | then
49 | echo >&2 "$topic is fully merged to master; better remove it."
50 | exit 1 ;# we could allow it, but there is no point.
51 | fi
52 |
53 | # Is topic ever merged to next? If so you should not be rebasing it.
54 | only_next_1=`git rev-list ^master "^$topic" ${publish} | sort`
55 | only_next_2=`git rev-list ^master ${publish} | sort`
56 | if test "$only_next_1" = "$only_next_2"
57 | then
58 | not_in_topic=`git rev-list "^$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
66 | else
67 | not_in_next=`git rev-list --pretty=oneline ^${publish} "$topic"`
68 | /usr/bin/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
89 | fi
90 |
91 | <<\DOC_END
92 |
93 | This sample hook safeguards topic branches that have been
94 | published from being rewound.
95 |
96 | The workflow assumed here is:
97 |
98 | * Once a topic branch forks from "master", "master" is never
99 | merged into it again (either directly or indirectly).
100 |
101 | * Once a topic branch is fully cooked and merged into "master",
102 | it is deleted. If you need to build on top of it to correct
103 | earlier mistakes, a new topic branch is created by forking at
104 | the tip of the "master". This is not strictly necessary, but
105 | it makes it easier to keep your history simple.
106 |
107 | * Whenever you need to test or publish your changes to topic
108 | branches, merge them into "next" branch.
109 |
110 | The script, being an example, hardcodes the publish branch name
111 | to be "next", but it is trivial to make it configurable via
112 | $GIT_DIR/config mechanism.
113 |
114 | With this workflow, you would want to know:
115 |
116 | (1) ... if a topic branch has ever been merged to "next". Young
117 | topic branches can have stupid mistakes you would rather
118 | clean up before publishing, and things that have not been
119 | merged into other branches can be easily rebased without
120 | affecting other people. But once it is published, you would
121 | not want to rewind it.
122 |
123 | (2) ... if a topic branch has been fully merged to "master".
124 | Then you can delete it. More importantly, you should not
125 | build on top of it -- other people may already want to
126 | change things related to the topic as patches against your
127 | "master", so if you need further changes, it is better to
128 | fork the topic (perhaps with the same name) afresh from the
129 | tip of "master".
130 |
131 | Let's look at this example:
132 |
133 | o---o---o---o---o---o---o---o---o---o "next"
134 | / / / /
135 | / a---a---b A / /
136 | / / / /
137 | / / c---c---c---c B /
138 | / / / \ /
139 | / / / b---b C \ /
140 | / / / / \ /
141 | ---o---o---o---o---o---o---o---o---o---o---o "master"
142 |
143 |
144 | A, B and C are topic branches.
145 |
146 | * A has one fix since it was merged up to "next".
147 |
148 | * B has finished. It has been fully merged up to "master" and "next",
149 | and is ready to be deleted.
150 |
151 | * C has not merged to "next" at all.
152 |
153 | We would want to allow C to be rebased, refuse A, and encourage
154 | B to be deleted.
155 |
156 | To compute (1):
157 |
158 | git rev-list ^master ^topic next
159 | git rev-list ^master next
160 |
161 | if these match, topic has not merged in next at all.
162 |
163 | To compute (2):
164 |
165 | git rev-list master..topic
166 |
167 | if this is empty, it is fully merged to "master".
168 |
169 | DOC_END