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 test-repo execbit
$ . "$TESTDIR/helpers-testrepo.sh"
$ cd "`dirname "$TESTDIR"`"
look for python scripts without the execute bit
$ testrepohg files 'set:**.py and not exec() and grep(r"^#!.*?python")'
[1]
look for python scripts with execute bit but not shebang
$ testrepohg files 'set:**.py and exec() and not grep(r"^#!.*?python")'
[1]
look for shell scripts with execute bit but not shebang
$ testrepohg files 'set:**.sh and exec() and not grep(r"^#!.*(ba)?sh")'
[1]
look for non scripts with no shebang
$ testrepohg files 'set:exec() and not **.sh and not **.py and not grep(r"^#!") and not contrib/openvms/**'
[1]