git-whats

#!/usr/bin/perl

$ENV{GIT_GET_NO_NEWLINE} = 1;

sub usage {
  die "Usage:\tgit-whats [commit-ish]
	git-whats --set 'description'
	git-whats --clear\n";
}

use Getopt::Long;
my $message_file = join "/",
  scalar(qx{git get repo-rootdir-relative}), ".what";
my $message;
my $clear;
GetOptions ("set=s"  => \$message,
            "clear"  => \$clear,
           )
  or usage();

if ($clear) {
  # --clear is incompatible with --set MESSAGE
  usage() if defined($message);
  $message = "";
}

if (defined $message) {
  usage() if @ARGV && (@ARGV != 1 || $ARGV[0] ne "HEAD");

  if ($message =~ /\S/) {
    $message .= "\n" unless $message =~ /\n\z/;
    open my($f), ">", $message_file
      or die "Couldn't write '$message_file': $!";
    print $f $message;
    system(qw(git add), $message_file) == 0
      or die sprintf "git-add '$message_file' failed with status %d\n",
        $? >> 8;
    system(qw(git commit --amend -C HEAD --), $message_file) == 0
      or die sprintf "git-commit -C HEAD failed with status %d\n",
        $? >> 8;
  } else {
    system(qw(git rm), $message_file) == 0
      or die sprintf "git-rm '$message_file' failed with status %d\n",
        $? >> 8;
    system(qw(git commit --amend -C HEAD)) == 0
      or die sprintf "git-commit -C HEAD failed with status %d\n",
        $? >> 8;
  }
  exit 0;
} else {
  my ($commit_ish) = shift @ARGV || 'HEAD';
  system(qw(git show), "$commit_ish:$message_file");
}