git-svn: warn instead of dying when commit data is missing

It is possible to have refs globbed by git-svn which stores data
purely in git; gently skip those instead of dying and assuming
user error.

ref: http://mid.gmane.org/CALi1mtdtNF_GtzyPTbfb7N51wwxsFY7zm8hsgwxr3tHcZZboyg@mail.gmail.com

Suggested-by: Jacob Godserv <jacobgodserv@gmail.com>
Cc: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

perl/Git/SVN.pm

@@ -97,8 +97,12 @@ sub resolve_local_globs {
 				    "existing: $existing\n",
 				    " globbed: $refname\n";
 			}
-			my $u = (::cmt_metadata("$refname"))[0] or die
-			    "$refname: no associated commit metadata\n";
+			my $u = (::cmt_metadata("$refname"))[0];
+			if (!defined($u)) {
+				warn
+"W: $refname: no associated commit metadata from SVN, skipping\n";
+				next;
+			}
 			$u =~ s!^\Q$url\E(/|$)!! or die
 			  "$refname: '$url' not found in '$u'\n";
 			if ($pathname ne $u) {