git commit message filter that adds the original committer timestamp to the comment. (This is due to the fact that it's impossible to specify a timestamp during TFS checkin.)

git_tfs_add_date.pl

#!/usr/bin/perl
#
# Execute with:
# 
# git filter-branch -f --msg-filter 'perl /path/to/git_tfs_add_date.pl' HEAD
#
use POSIX;

open INPUT, "<-";
$ENV{'GIT_COMMITTER_DATE'} =~ /^@(.*) \+(\d\d)(\d\d)/;
# Unix timestamp, timezone hours, timezone minutes
($c,$zh,$zm) = ($1,$2,$3);
$comment = join('', <INPUT>);

# Convert into time_t without system timezone offseting
# but add the timezone ourselves
$time = gmtime ($c + (3600*$zh) + $zm);
$iso_date = strftime("%Y-%m-%d %H:%M:%S", $time);
# Format the comment date
$comment_date = "${iso_date} +$zh$zm";

# Chop off the last newline, so we could check whether the comment is empty
chomp $comment;

# If there's a comment, print the comment with two pending newlines
print "$comment$/$/" if ($comment ne '');

# Avoid printing last EOL so TFS comments won't have a trailing empty line
print "(git timestamp: ${comment_date})"