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 unix-permissions no-root reporevlogstore
#testcases dirstate-v1 dirstate-v2
#if dirstate-v2
$ cat >> $HGRCPATH << EOF
> [format]
> use-dirstate-v2=1
> [storage]
> dirstate-v2.slow-path=allow
> EOF
#endif
$ hg init t
$ cd t
$ echo foo > a
$ hg add a
$ hg commit -m "1"
$ hg verify -q
$ chmod -r .hg/store/data/a.i
$ hg verify -q
abort: $EACCES$: '$TESTTMP/t/.hg/store/data/a.i'
[255]
$ chmod +r .hg/store/data/a.i
$ hg verify -q
$ chmod -w .hg/store/data/a.i
$ echo barber > a
$ hg commit -m "2"
trouble committing a!
abort: $EACCES$: '$TESTTMP/t/.hg/store/data/a.i'
[255]
$ chmod -w .
$ hg diff --nodates
diff -r 2a18120dc1c9 a
--- a/a
+++ b/a
@@ -1,1 +1,1 @@
-foo
+barber
$ chmod +w .
$ chmod +w .hg/store/data/a.i
$ mkdir dir
$ touch dir/a
$ hg status
M a
? dir/a
$ chmod -rx dir
#if no-fsmonitor
(fsmonitor makes "hg status" avoid accessing to "dir")
$ hg status
dir: $EACCES$* (glob)
M a
#endif
Reenable perm to allow deletion:
$ chmod +rx dir
$ cd ..