Store empty (default) branch in branch cache, too.
Operations on this branch don't work otherwise.
Reading branches.cache had to be adjusted to allow an empty label.
Adjusted reading of the cache tip for symmetry, no functional change here.
adding a
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% should fail because not at a head
abort: repo has 3 heads - please merge with an explicit rev
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% should fail because > 2 heads
abort: repo has 3 heads - please merge with an explicit rev
% should succeed
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
% should succeed - 2 heads
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
% should fail because 1 head
abort: there is nothing to merge - use "hg update" instead