templates/hooks--pre-rebase

   1 #!/bin/sh
   2 #
   3 # Copyright (c) 2006 Junio C Hamano
   4 #
   5
   6 publish=next
   7 basebranch="$1"
   8 if test "$#" = 2
   9 then
  10         topic="refs/heads/$2"
  11 else
  12         topic=`git symbolic-ref HEAD`
  13 fi
  14
  15 case "$basebranch,$topic" in
  16 master,refs/heads/??/*)
  17         ;;
  18 *)
  19         exit 0 ;# we do not interrupt others.
  20         ;;
  21 esac
  22
  23 # Now we are dealing with a topic branch being rebased
  24 # on top of master.  Is it OK to rebase it?
  25
  26 # Is topic fully merged to master?
  27 not_in_master=`git-rev-list --pretty=oneline ^master "$topic"`
  28 if test -z "$not_in_master"
  29 then
  30         echo >&2 "$topic is fully merged to master; better remove it."
  31         exit 1 ;# we could allow it, but there is no point.
  32 fi
  33
  34 # Is topic ever merged to next?  If so you should not be rebasing it.
  35 only_next_1=`git-rev-list ^master "^$topic" ${publish} | sort`
  36 only_next_2=`git-rev-list ^master           ${publish} | sort`
  37 if test "$only_next_1" = "$only_next_2"
  38 then
  39         not_in_topic=`git-rev-list "^$topic" master`
  40         if test -z "$not_in_topic"
  41         then
  42                 echo >&2 "$topic is already up-to-date with master"
  43                 exit 1 ;# we could allow it, but there is no point.
  44         else
  45                 exit 0
  46         fi
  47 else
  48         not_in_next=`git-rev-list --pretty=oneline ^${publish} "$topic"`
  49         perl -e '
  50                 my $topic = $ARGV[0];
  51                 my $msg = "* $topic has commits already merged to public branch:\n";
  52                 my (%not_in_next) = map {
  53                         /^([0-9a-f]+) /;
  54                         ($1 => 1);
  55                 } split(/\n/, $ARGV[1]);
  56                 for my $elem (map {
  57                                 /^([0-9a-f]+) (.*)$/;
  58                                 [$1 => $2];
  59                         } split(/\n/, $ARGV[2])) {
  60                         if (!exists $not_in_next{$elem->[0]}) {
  61                                 if ($msg) {
  62                                         print STDERR $msg;
  63                                         undef $msg;
  64                                 }
  65                                 print STDERR " $elem->[1]\n";
  66                         }
  67                 }
  68         ' "$topic" "$not_in_next" "$not_in_master"
  69         exit 1
  70 fi
  71
  72 exit 0
  73
  74 ################################################################
  75
  76 This sample hook safeguards topic branches that have been
  77 published from being rewound.
  78
  79 The workflow assumed here is:
  80
  81  * Once a topic branch forks from "master", "master" is never
  82    merged into it again (either directly or indirectly).
  83
  84  * Once a topic branch is fully cooked and merged into "master",
  85    it is deleted.  If you need to build on top of it to correct
  86    earlier mistakes, a new topic branch is created by forking at
  87    the tip of the "master".  This is not strictly necessary, but
  88    it makes it easier to keep your history simple.
  89
  90  * Whenever you need to test or publish your changes to topic
  91    branches, merge them into "next" branch.
  92
  93 The script, being an example, hardcodes the publish branch name
  94 to be "next", but it is trivial to make it configurable via
  95 $GIT_DIR/config mechanism.
  96
  97 With this workflow, you would want to know:
  98
  99 (1) ... if a topic branch has ever been merged to "next".  Young
 100     topic branches can have stupid mistakes you would rather
 101     clean up before publishing, and things that have not been
 102     merged into other branches can be easily rebased without
 103     affecting other people.  But once it is published, you would
 104     not want to rewind it.
 105
 106 (2) ... if a topic branch has been fully merged to "master".
 107     Then you can delete it.  More importantly, you should not
 108     build on top of it -- other people may already want to
 109     change things related to the topic as patches against your
 110     "master", so if you need further changes, it is better to
 111     fork the topic (perhaps with the same name) afresh from the
 112     tip of "master".
 113
 114 Let's look at this example:
 115
 116                    o---o---o---o---o---o---o---o---o---o "next"
 117                   /       /           /           /
 118                  /   a---a---b A     /           /
 119                 /   /               /           /
 120                /   /   c---c---c---c B         /
 121               /   /   /             \         /
 122              /   /   /   b---b C     \       /
 123             /   /   /   /             \     /
 124     ---o---o---o---o---o---o---o---o---o---o---o "master"
 125
 126
 127 A, B and C are topic branches.
 128
 129  * A has one fix since it was merged up to "next".
 130
 131  * B has finished.  It has been fully merged up to "master" and "next",
 132    and is ready to be deleted.
 133
 134  * C has not merged to "next" at all.
 135
 136 We would want to allow C to be rebased, refuse A, and encourage
 137 B to be deleted.
 138
 139 To compute (1):
 140
 141         git-rev-list ^master ^topic next
 142         git-rev-list ^master        next
 143
 144         if these match, topic has not merged in next at all.
 145
 146 To compute (2):
 147
 148         git-rev-list master..topic
 149
 150         if this is empty, it is fully merged to "master".