Andrew's git - gitweb.git/blob - templates/hooks--pre-rebase.sample

   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
  18publish=next
  19basebranch="$1"
  20if test "$#" = 2
  21then
  22        topic="refs/heads/$2"
  23else
  24        topic=`git symbolic-ref HEAD` ||
  25        exit 0 ;# we do not interrupt rebasing detached HEAD
  26fi
  27
  28case "$topic" in
  29refs/heads/??/*)
  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
  39# Does the topic really exist?
  40git show-ref -q "$topic" || {
  41        echo >&2 "No such branch $topic"
  42        exit 1
  43}
  44
  45# Is topic fully merged to master?
  46not_in_master=`git rev-list --pretty=oneline ^master "$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_PATH@ -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".