pre-rebase.sh

$ mv pre-rebase.sample pre-rebase #renaming sample to pre-rebase.
#!/bin/sh
publish=next
basebranch="$1"
if test "$#" = 2
then
 topic="refs/heads/$2"
else
 topic=`git symbolic-ref HEAD` ||
 exit 0 ;# we do not interrupt rebasing detached HEAD
fi
case "$topic" in
refs/heads/??/*)
 ;;
*)
 exit 0 ;# we do not interrupt others.
 ;;
esac
# Now we are dealing with a topic branch being rebased
# on top of master.  Is it OK to rebase it?
# Does the topic really exist?
git show-ref -q "$topic" || {
 echo >&2 "No such branch $topic"
 exit 1
}
# Is topic fully merged to master?
not_in_master=`git rev-list --pretty=oneline ^master "$topic"`
if test -z "$not_in_master"
then
 echo >&2 "$topic is fully merged to master; better remove it."
 exit 1 ;# we could allow it, but there is no point.
fi
# Is topic ever merged to next?  If so you should not be rebasing it.
only_next_1=`git rev-list ^master "^$topic" ${publish} | sort`
only_next_2=`git rev-list ^master           ${publish} | sort`
if test "$only_next_1" = "$only_next_2"
then
 not_in_topic=`git rev-list "^$topic" master`
 if test -z "$not_in_topic"
 then
  echo >&2 "$topic is already up-to-date with master"
  exit 1 ;# we could allow it, but there is no point.
 else
  exit 0
 fi
else
 not_in_next=`git rev-list --pretty=oneline ^${publish} "$topic"`
 /usr/bin/perl -e '
  my $topic = $ARGV[0];
  my $msg = "* $topic has commits already merged to public branch:\n";
  my (%not_in_next) = map {
   /^([0-9a-f]+) /;
   ($1 => 1);
  } split(/\n/, $ARGV[1]);
  for my $elem (map {
    /^([0-9a-f]+) (.*)$/;
    [$1 => $2];
   } split(/\n/, $ARGV[2])) {
   if (!exists $not_in_next{$elem->[0]}) {
    if ($msg) {
     print STDERR $msg;
     undef $msg;
    }
    print STDERR " $elem->[1]\n";
   }
  }
 ' "$topic" "$not_in_next" "$not_in_master"
 exit 1
fi