import: convert init.defaultBranch to fully qualified ref

init.defaultBranch expects a branch name, not a fully qualified ref.
git-init prepends "refs/heads/" automatically and unconditionally.

PublicInbox::Import::default_branch, however, incorrectly passes on
the init.defaultBranch value as is, leading to it being used in spots
where a fully qualified ref is required.  For example, with an
init.defaultBranch value of "master", public-inbox-index for a v2
repository would lead to an all.git repository where HEAD's content is
"ref: master" instead of "ref: refs/heads/master".

Prepend "refs/heads/" to the incoming init.defaultBranch value.

Fixes: 7c2f36de2fb49dd7 (import: respect init.defaultBranch)

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/PublicInbox/Import.pm b/lib/PublicInbox/Import.pm
index 46f57e27..3adf9dec 100644
--- a/lib/PublicInbox/Import.pm
+++ b/lib/PublicInbox/Import.pm
@@ -25,7 +25,7 @@ sub default_branch () {
                                  { GIT_CONFIG => undef });
                 chomp(my $h = <$r> // '');
                 close $r;
-                $h eq '' ? 'refs/heads/master' : $h;
+                $h eq '' ? 'refs/heads/master' : "refs/heads/$h";
         }
 }