branchcache: add a "pure topological head" fast path
In a narrow but actually quick common case, all topological heads are all on
the same branch and all open. In this case, computing the branch map is very
simple. We can quickly detect situation where this situation will not change.
So we update the V3 format to be able to express this situation and upgrade the
update code to detect we remains in that mode.
The branch cache is populated with the actual value when the branch map is
accessed, but the update_disk method can do the update without needing to
populate it.
$ cat >> $HGRCPATH << EOF
> [extensions]
> strip=
> EOF
Setup repo
$ hg init repo
$ cd repo
Test backups list and recover
$ hg debugbackupbundle
no backup changesets found
$ mkcommit() {
> echo "$1" > "$1"
> hg add "$1"
> hg ci -l $1
> }
$ mkcommit a
$ mkcommit b
$ hg strip .
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
saved backup bundle to $TESTTMP/repo/.hg/strip-backup/d2ae7f538514-2953539b-backup.hg
$ hg debugbackupbundle
Recover changesets using: hg debugbackupbundle --recover <changeset hash>
Available backup changesets:
* (glob)
d2ae7f538514 b
$ hg debugbackupbundle --recover d2ae7f538514
Unbundling d2ae7f538514
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets d2ae7f538514 (1 drafts)