git-svn: Don't rely on $_ after making a function call

Many functions and operators in perl set $_, so its value cannot be relied upon
after calling arbitrary functions. The solution is simply to copy the value of
$_ into a local variable that will not get overwritten.

Signed-off-by: Adam Roben <aroben@apple.com>
Acked-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-svn.perl

diff --git a/git-svn.perl b/git-svn.perl
index 077d6b3..90f3bc1 100755
--- a/git-svn.perl
+++ b/git-svn.perl
@@ -771,19 +771,19 @@
 sub working_head_info {
 	my ($head, $refs) = @_;
 	my ($fh, $ctx) = command_output_pipe('rev-list', $head);
-	while (<$fh>) {
-		chomp;
-		my ($url, $rev, $uuid) = cmt_metadata($_);
+	while (my $hash = <$fh>) {
+		chomp($hash);
+		my ($url, $rev, $uuid) = cmt_metadata($hash);
 		if (defined $url && defined $rev) {
 			if (my $gs = Git::SVN->find_by_url($url)) {
 				my $c = $gs->rev_db_get($rev);
-				if ($c && $c eq $_) {
+				if ($c && $c eq $hash) {
 					close $fh; # break the pipe
 					return ($url, $rev, $uuid, $gs);
 				}
 			}
 		}
-		unshift @$refs, $_ if $refs;
+		unshift @$refs, $hash if $refs;
 	}
 	command_close_pipe($fh, $ctx);
 	(undef, undef, undef, undef);