From: Junio C Hamano <junkio@cox.net>
Date: Wed, 20 Sep 2006 15:53:12 GMT
Subject: Re: [PATCH] cvsimport move over to using git for each ref to read refs
Message-ID: <7vodtak00n.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <4511173D.7020702@shadowen.org>

Andy Whitcroft <apw@shadowen.org> writes:

> I guess we could teach for-each-ref to output this as well?  Perhaps
> something like authorstamp?

I think you can work with "author" or "committer" to grab the
whole raw line.

About the quoting and parsing, language specific quoting mode is
meant for git-for-each-ref to produce a string that can be eval'ed
in the host language.  Think of the command as a tool to write a
short program for you.

The original is like this:

	# Get the last import timestamps
	opendir(D,"$git_dir/refs/heads");
	while(defined(my $head = readdir(D))) {
		next if $head =~ /^\./;
		open(F,"$git_dir/refs/heads/$head")
			or die "Bad head branch: $head: $!\n";
		chomp(my $ftag = <F>);
		close(F);
		open(F,"git-cat-file commit $ftag |");
		while(<F>) {
			next unless /^author\s.*\s(\d+)\s[-+]\d{4}$/;
			$branch_date{$head} = $1;
			last;
		}
		close(F);
	}
	closedir(D);

The purpose of the loop is to grab all branch heads, and grab
author timestamp for all of them, _and_ stash that in
%branch_date hash indexed by head name.  You would want to have
something like this executed for each branch:

	$refname = %(refname);
	$authorline = %(author);
	$authorline =~ /^author\s.*\s(\d+)\s[-+]\d{4}$/;
        $branch_date{$refname} = $1;

So, you have the tool to write such a program for you, by doing
something like this:

	my $template = '
                $refname = %(refname);
                $authorline = %(author);
                $authorline =~ /^author\s.*\s(\d+)\s[-+]\d{4}$/;
                $branch_date{$refname} = $1;
	';
        my @cmd = ('git-for-each-ref', '--perl', "--format=$template");

	open I, '-|', @cmd, 'refs/heads';
        my $script = join('',<I>);
        close I;

	my ($refname, $authorline);
        eval "$script";

The language specific quoting flag --perl affects how %() are
interpolated into the generated program text as literals.
That's why there is no quote around %(refname) or %(author)
in the example above when defining the $template.