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
  91<<\DOC_END
  92
  93This sample hook safeguards topic branches that have been
  94published from being rewound.
  95
  96The 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
 110The script, being an example, hardcodes the publish branch name
 111to be "next", but it is trivial to make it configurable via
 112$GIT_DIR/config mechanism.
 113
 114With 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
 131Let'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
 144A, 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
 153We would want to allow C to be rebased, refuse A, and encourage
 154B to be deleted.
 155
 156To 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
 163To compute (2):
 164
 165        git rev-list master..topic
 166
 167        if this is empty, it is fully merged to "master".
 168
 169DOC_END