I started running into trouble though, because it didn't understand the .gitignore file (which has the same format as the .cvsignore). I began adding clumsy glob support to my app, but it presented more trouble than I whould have thought. I ended up using open my $in, '-|', qw(git ls-files) or die $! to find the applicable files — since git knows how to list the files it's watching as a built in function. This fits well with the overall git model, because it's a collection of scripts that work together; but I'm still interested in how you'd do it in perl.

There's no way to guess the git revision before the commit, so instead of the revision I ended up using a Digest::SHA1 that skips the contents of the rcs tags. Actually, I prepend the number of lines and the number of bytes in the file also. For the $Date$ I used the mtime of the file.

my $h    = $sha1->b64digest;
my $rev  = "$lines.$bytes.$h"; $rev =~ tr/$/_/;
my $date = strftime('%Y-%m-%d %H:%M:%S UTC', gmtime($mtime));
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My main question is concerning the best way to find all the files git finds. Before I thought to use qw(git ls-files) I was going to try opendir and build up a list of globs found in the .gitignore files I found along the way. (Something like the following, which is obviously incomplete.)

use warnings;
use strict;
use Text::Glob qw(glob_to_regex);

sub do_a_dir {
    my $dir   = shift;
    my @globs = @_;
    my @files = ();

    opendir my $dir, $dir or die "hrmph: $!";
    while( my $ent = readdir $dir ) {
        next if $ent =~ m/\A\.\.?\z/;

        if( -d $ent ) {
            push @files, &do_a_dir(@globs) unless &a_glob_matches($ent
+, @globs);

        } elsif( -f $ent ) {
            if( $ent eq ".gitignore" ) {
                open my $in, $ent or die "hrmph: $!";
                while(<$in>) {
                    chomp;
                    push @globs, glob_to_regex( $_ );
                }
                close $in;

            } else {
                push @files, $ent unless &a_glob_matches($ent, @globs)
+;
                # although, this is spurious.  In practice, I would ne
+ed
                # to find all the .gitignores in this dir before I
                # can test the files.
            }

        } else {
            # agahrr, I don't want to think about these monsters right
+ now
            # I probably mean to skip them if I'm using opendir...
        }
    }
    closedir $dir;
}

sub a_glob_matches {
    my $ent = shift;
    my @globs = @_;
    
    for( @globs ) {
        return 1 if $ent =~ $_;
    }

    return 0;
}
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