git-svn: fix fetch with deleted tag

Currently git-svn assumes that two tags created from the same
revision will have the same repo url, so it uses a ref to the
tag without checking that its url matches the current url.

This causes issues when fetching an svn repo where a tag was
created, deleted, and then recreated under the following
circumstances:

- Both tags were copied from the same revision.
- Both tags had the same name.
- Both tags had different repository paths.
- [Optional] Both tags have a file with the same name but
  different content.

When all four conditions are met, a checksum mismatch error
occurs because the content of two files with the same path
differs (see t/t9155--git-svn-fetch-deleted-tag.sh):

    Checksum mismatch: ChangeLog 065854....
    expected: ce771b....
         got: 9563fd....

When only the first three conditions are met, no error occurs
but the tag in git matches the first (deleted) tag instead of
the last (most recent) tag (see
t/t9156-git-svn-fetch-deleted-tag-2.sh).

The fix is to verify that the repo url for the ref matches the
current url.  If the urls do not match, then a "tail" is grown
on the tag name by appending a dash and rechecking the new ref's
repo url until either a matching repo url is found or a new tag
is created.

Signed-off-by: David D. Kilzer <ddkilzer@kilzer.net>
Acked-by: Eric Wong <normalperson@yhbt.net>

1 files changed, 13 insertions, 2 deletions

diff --git a/git-svn.perl b/git-svn.perl
index 39bcb45593..9b046b693f 100755
--- a/git-svn.perl
+++ b/git-svn.perl
@@ -2963,14 +2963,25 @@ sub other_gs {
 		$ref_id .= "\@$r";
 		# just grow a tail if we're not unique enough :x
 		$ref_id .= '-' while find_ref($ref_id);
-		print STDERR "Initializing parent: $ref_id\n" unless $::_q > 1;
 		my ($u, $p, $repo_id) = ($new_url, '', $ref_id);
 		if ($u =~ s#^\Q$url\E(/|$)##) {
 			$p = $u;
 			$u = $url;
 			$repo_id = $self->{repo_id};
 		}
-		$gs = Git::SVN->init($u, $p, $repo_id, $ref_id, 1);
+		while (1) {
+			# It is possible to tag two different subdirectories at
+			# the same revision.  If the url for an existing ref
+			# does not match, we must either find a ref with a
+			# matching url or create a new ref by growing a tail.
+			$gs = Git::SVN->init($u, $p, $repo_id, $ref_id, 1);
+			my (undef, $max_commit) = $gs->rev_map_max(1);
+			last if (!$max_commit);
+			my ($url) = ::cmt_metadata($max_commit);
+			last if ($url eq $gs->full_url);
+			$ref_id .= '-';
+		}
+		print STDERR "Initializing parent: $ref_id\n" unless $::_q > 1;
 	}
 	$gs
 }