directory refactor: open_main_gitattrs confesses if $maindir not set

This improves the error message considerably for "didn't call
record_maindir" bugs.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

1 files changed, 1 insertions, 0 deletions

diff --git a/dgit b/dgit
index 6c1d5bc..8b638c4 100755
--- a/dgit
+++ b/dgit
@@ -3314,6 +3314,7 @@ sub ensure_setup_existing_tree () {
 }
 
 sub open_main_gitattrs () {
+    confess 'internal error no maindir' unless defined $maindir;
     my $gai = new IO::File "$maindir_gitcommon/info/attributes"
 	or $!==ENOENT
 	or die "open $maindir_gitcommon/info/attributes: $!";