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.
# foo-%nof%N.patch
exporting patches:
foo-01of10.patch
foo-02of10.patch
foo-03of10.patch
foo-04of10.patch
foo-05of10.patch
foo-06of10.patch
foo-07of10.patch
foo-08of10.patch
foo-09of10.patch
foo-10of10.patch
# foo-%%%H.patch
exporting patches:
foo-%617188a1c80f869a7b66c85134da88a6fb145f67.patch
foo-%dd41a5ff707a5225204105611ba49cc5c229d55f.patch
foo-%f95a5410f8664b6e1490a4af654e4b7d41a7b321.patch
foo-%4346bcfde53b4d9042489078bcfa9c3e28201db2.patch
foo-%afda8c3a009cc99449a05ad8aa4655648c4ecd34.patch
foo-%35284ce2b6b99c9d2ac66268fe99e68e1974e1aa.patch
foo-%9688c41894e6931305fa7165a37f6568050b4e9b.patch
foo-%747d3c68f8ec44bb35816bfcd59aeb50b9654c2f.patch
foo-%5f17a83f5fbd9414006a5e563eab4c8a00729efd.patch
foo-%f3acbafac161ec68f1598af38f794f28847ca5d3.patch
# foo-%b-%R.patch
exporting patches:
foo-repo-2.patch
foo-repo-3.patch
foo-repo-4.patch
foo-repo-5.patch
foo-repo-6.patch
foo-repo-7.patch
foo-repo-8.patch
foo-repo-9.patch
foo-repo-10.patch
foo-repo-11.patch
# foo-%h.patch
exporting patches:
foo-617188a1c80f.patch
foo-dd41a5ff707a.patch
foo-f95a5410f866.patch
foo-4346bcfde53b.patch
foo-afda8c3a009c.patch
foo-35284ce2b6b9.patch
foo-9688c41894e6.patch
foo-747d3c68f8ec.patch
foo-5f17a83f5fbd.patch
foo-f3acbafac161.patch
# foo-%r.patch
exporting patches:
foo-02.patch
foo-03.patch
foo-04.patch
foo-05.patch
foo-06.patch
foo-07.patch
foo-08.patch
foo-09.patch
foo-10.patch
foo-11.patch