#!/usr/bin/perl
# Convert git log output to ChangeLog format.

my $VERSION = '2008-12-21 12:07'; # UTC
# The definition above must lie within the first 8 lines in order
# for the Emacs time-stamp write hook (at end) to update it.
# If you change this file with Emacs, please let the write hook
# do its job.  Otherwise, update this string manually.

# Copyright (C) 2008 Free Software Foundation, Inc.

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# Written by Jim Meyering

use strict;
use warnings;
use Getopt::Long;
use POSIX qw(strftime);

(my $ME = $0) =~ s|.*/||;

# use File::Coda; # http://meyering.net/code/Coda/
END {
  defined fileno STDOUT or return;
  close STDOUT and return;
  warn "$ME: failed to close standard output: $!\n";
  $? ||= 1;
}

sub usage ($)
{
  my ($exit_code) = @_;
  my $STREAM = ($exit_code == 0 ? *STDOUT : *STDERR);
  if ($exit_code != 0)
    {
      print $STREAM "Try `$ME --help' for more information.\n";
    }
  else
    {
      print $STREAM <<EOF;
Usage: $ME [OPTIONS] [ARGS]

Convert git log output to ChangeLog format.  If present, any ARGS
are passed to "git log".  To avoid ARGS being parsed as options to
$ME, they may be preceded by '--'.

OPTIONS:

   --since=DATE convert only the logs since DATE;
                  the default is to convert all log entries.

   --help       display this help and exit
   --version    output version information and exit

EXAMPLE:

  $ME --since=2008-01-01 > ChangeLog
  $ME -- -n 5 foo > last-5-commits-to-branch-foo

EOF
    }
  exit $exit_code;
}

# If the string $S is a well-behaved file name, simply return it.
# If it contains white space, quotes, etc., quote it, and return the new string.
sub shell_quote($)
{
  my ($s) = @_;
  if ($s =~ m![^\w+/.,-]!)
    {
      # Convert each single quote to '\''
      $s =~ s/\'/\'\\\'\'/g;
      # Then single quote the string.
      $s = "'$s'";
    }
  return $s;
}

sub quoted_cmd(@)
{
  return join (' ', map {shell_quote $_} @_);
}

{
  my $since_date = '1970-01-01 UTC';
  GetOptions
    (
     help => sub { usage 0 },
     version => sub { print "$ME version $VERSION\n"; exit },
     'since=s' => \$since_date,
    ) or usage 1;

  my @cmd = (qw (git log --log-size), "--since=$since_date",
             '--pretty=format:%ct  %an  <%ae>%n%n%s%n%b%n', @ARGV);
  open PIPE, '-|', @cmd
    or die ("$ME: failed to run `". quoted_cmd (@cmd) ."': $!\n"
            . "(Is your Git too old?  Version 1.5.1 or later is required.)\n");

  my $prev_date_line = '';
  while (1)
    {
      defined (my $in = <PIPE>)
        or last;
      $in =~ /^log size (\d+)$/
        or die "$ME:$.: Invalid line (expected log size):\n$in";
      my $log_nbytes = $1;

      my $log;
      my $n_read = read PIPE, $log, $log_nbytes;
      $n_read == $log_nbytes
        or die "$ME:$.: unexpected EOF\n";

      my @line = split "\n", $log;
      my $author_line = shift @line;
      defined $author_line
        or die "$ME:$.: unexpected EOF\n";
      $author_line =~ /^(\d+)  (.*>)$/
        or die "$ME:$.: Invalid line "
          . "(expected date/author/email):\n$author_line\n";

      my $date_line = sprintf "%s  $2\n", strftime ("%F", localtime ($1));
      # If this line would be the same as the previous date/name/email
      # line, then arrange not to print it.
      if ($date_line ne $prev_date_line)
        {
          $prev_date_line eq ''
            or print "\n";
          print $date_line;
        }
      $prev_date_line = $date_line;

      # Omit "Signed-off-by..." lines.
      @line = grep !/^Signed-off-by: .*>$/, @line;

      # Remove leading and trailing blank lines.
      while ($line[0] =~ /^\s*$/) { shift @line; }
      while ($line[$#line] =~ /^\s*$/) { pop @line; }

      # Prefix each non-empty line with a TAB.
      @line = map { length $_ ? "\t$_" : '' } @line;

      print "\n", join ("\n", @line), "\n";

      defined ($in = <PIPE>)
        or last;
      $in ne "\n"
        and die "$ME:$.: unexpected line:\n$in";
    }

  close PIPE
    or die "$ME: error closing pipe from " . quoted_cmd (@cmd) . "\n";
  # FIXME-someday: include $PROCESS_STATUS in the diagnostic
}

# Local Variables:
# indent-tabs-mode: nil
# eval: (add-hook 'write-file-hooks 'time-stamp)
# time-stamp-start: "my $VERSION = '"
# time-stamp-format: "%:y-%02m-%02d %02H:%02M"
# time-stamp-time-zone: "UTC"
# time-stamp-end: "'; # UTC"
# End:
