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.
#testcases dirstate-v1 dirstate-v2
#if dirstate-v2
$ cat >> $HGRCPATH << EOF
> [format]
> use-dirstate-v2=1
> [storage]
> dirstate-v2.slow-path=allow
> EOF
#endif
The proliferation of status implementations can be confusing:
- The pure python implementation:
(no-rhg pure !)
- The C implementation:
(no-rhg no-rust no-pure !)
- The two rust implementations:
(rhg !)
(no-rhg rust !)
$ hg init repo1
$ cd repo1
$ mkdir d1
$ touch d1/x
$ hg commit -Am.
adding d1/x
$ touch d1/y
$ chmod -r d1
$ hg status
d1: $EACCES$
! d1/x (rhg !)
! d1/x (no-rhg rust !)
$ hg status
d1: $EACCES$
! d1/x (rust !)
! d1/x (no-rust rhg !)
$ chmod +r d1
$ hg status
? d1/y
$ touch d1/z
$ hg status
? d1/y
? d1/z