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 exit 0
  92
  93 ################################################################
  94
  95 This sample hook safeguards topic branches that have been
  96 published from being rewound.
  97
  98 The 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
 112 The script, being an example, hardcodes the publish branch name
 113 to be "next", but it is trivial to make it configurable via
 114 $GIT_DIR/config mechanism.
 115
 116 With 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
 133 Let'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
 146 A, 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
 155 We would want to allow C to be rebased, refuse A, and encourage
 156 B to be deleted.
 157
 158 To 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
 165 To compute (2):
 166
 167         git rev-list master..topic
 168
 169         if this is empty, it is fully merged to "master".