git-merge-all

#!/usr/bin/perl

use strict;
use warnings;

my $headref = `git symbolic-ref HEAD`;
if (my ($head) = ($headref =~ m!^refs/heads/(.*)!)) {
  my $fh;
  unless (open($fh, '-|', qw[git branch -r --no-merge HEAD])) {
    print STDERR "Couldn't execute 'git branch -r --no-merge HEAD': $!\n";
    exit(1);
  }
  my @branches;
  while (<$fh>) {
    chomp;
    if (my ($branch) = m!^\s+([^/]+/\Q$head\E)$!) {
      push(@branches, $branch);
    }
  }
  if (@branches) {
    print STDERR "git merge ", join(' ', @branches), "\n";
    (system(qw[git merge], @branches) == 0) or die $!;
 } else {
    print STDERR "Already up-to-date.\n";
  }
} else {
  print STDERR "HEAD is at '$headref', which doesn't look like a branch\n";
}