git-svn: Make branch use correct svn-remote

The 'branch' subcommand incorrectly had the svn-remote to use hardcoded
as 'svn', the default remote name.  This meant that branches derived
from other svn-remotes would try to use the branch and tag configuration
for the 'svn' remote, potentially copying would-be branches to the wrong
place in SVN, into the branch namespace for another project.

Fix this by using the remote name extracted from the svn info for the
specified git ref.  Add a testcase for this behaviour.

[jc: squashed in a fix to test from Michael J Gruber for older svn (1.4)]

Signed-off-by: Deskin Miller <deskinm@umich.edu>
Acked-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/git-svn.perl b/git-svn.perl
index 914c707..e64e97b 100755
--- a/git-svn.perl
+++ b/git-svn.perl
@@ -558,7 +558,7 @@
 
 	my ($src, $rev, undef, $gs) = working_head_info($head);
 
-	my $remote = Git::SVN::read_all_remotes()->{svn};
+	my $remote = Git::SVN::read_all_remotes()->{$gs->{repo_id}};
 	my $glob = $remote->{ $_tag ? 'tags' : 'branches' };
 	my ($lft, $rgt) = @{ $glob->{path} }{qw/left right/};
 	my $dst = join '/', $remote->{url}, $lft, $branch_name, ($rgt || ());
diff --git a/t/t9128-git-svn-cmd-branch.sh b/t/t9128-git-svn-cmd-branch.sh
index 47c4d4d..252daa7 100755
--- a/t/t9128-git-svn-cmd-branch.sh
+++ b/t/t9128-git-svn-cmd-branch.sh
@@ -56,4 +56,23 @@
 	test_must_fail git svn tag tag1
 '
 
+test_expect_success 'branch uses correct svn-remote' '
+	(svn co "$svnrepo" svn &&
+	cd svn &&
+	mkdir mirror &&
+	svn add mirror &&
+	svn copy trunk mirror/ &&
+	svn copy tags mirror/ &&
+	svn copy branches mirror/ &&
+	svn ci -m "made mirror" ) &&
+	rm -rf svn &&
+	git svn init -s -R mirror --prefix=mirror/ "$svnrepo"/mirror &&
+	git svn fetch -R mirror &&
+	git checkout mirror/trunk &&
+	base=$(git rev-parse HEAD:) &&
+	git svn branch -m "branch in mirror" d &&
+	test $base = $(git rev-parse remotes/mirror/d:) &&
+	test_must_fail git rev-parse remotes/d
+'
+
 test_done