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
  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         @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
  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