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.
#require no-symlink
# The following script was used to create the bundle:
#
# hg init symlinks
# cd symlinks
# echo a > a
# mkdir d
# echo b > d/b
# ln -s a a.lnk
# ln -s d/b d/b.lnk
# hg ci -Am t
# hg bundle --base null ../test-no-symlinks.hg
Extract a symlink on a platform not supporting them
$ hg init t
$ cd t
$ hg pull -q "$TESTDIR/bundles/test-no-symlinks.hg"
$ hg update
4 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cat a.lnk && echo
a
$ cat d/b.lnk && echo
d/b
Copy a symlink and move another
$ hg copy a.lnk d/a2.lnk
$ hg mv d/b.lnk b2.lnk
$ hg ci -Am copy
$ cat d/a2.lnk && echo
a
$ cat b2.lnk && echo
d/b
Bundle and extract again
$ hg bundle --base null ../symlinks.hg
2 changesets found
$ cd ..
$ hg init t2
$ cd t2
$ hg pull ../symlinks.hg
pulling from ../symlinks.hg
requesting all changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 6 changes to 6 files
new changesets d326ae2d01ee:71d85cf3ba90 (2 drafts)
(run 'hg update' to get a working copy)
$ hg update
5 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cat a.lnk && echo
a
$ cat d/a2.lnk && echo
a
$ cat b2.lnk && echo
d/b