match: strengthen visit_children_set invariant, Recursive means "all files"
My previous interpretation of "Recursive" was too relaxed: I thought it
instructed the caller to do something like this:
> you can stop calling `visit_children_set` because you'll need to descend into
> every directory recursively, but you should still check every file if it
> matches or not
Whereas the real instruction seems to be:
> I guarantee that everything in this subtree matches, you can stop
> querying the matcher for all files and dirs altogether.
The evidence to support this:
- the test actually passes with the stronger invariant, revealing no
exceptions from this rule
- the implementation of `visit_children_set` for `DifferenceMatcher`
clearly relies on this requirement, so it must hold for that not to
lead to bugs.
#require execbit
$ hg init repo
$ cd repo
$ echo foo > foo
$ chmod 644 foo
$ hg ci -qAm '644'
$ chmod 755 foo
$ hg ci -qAm '755'
reverting to rev 0
$ hg revert -a -r 0
reverting foo
$ hg st
M foo
$ hg diff --git
diff --git a/foo b/foo
old mode 100755
new mode 100644
$ cd ..