context: don't complain about a matcher's subrepo paths in changectx.walk()
Previously, the first added test printed the following:
$ hg files -S -r '.^' sub1/sub2/folder
sub1/sub2/folder: no such file in rev 9bb10eebee29
sub1/sub2/folder: no such file in rev 9bb10eebee29
sub1/sub2/folder/test.txt
One warning occured each time a subrepo was crossed into.
The second test ensures that the matcher copy stays in place. Without the copy,
the bad() function becomes an increasingly longer chain, and no message would be
printed out for a file missing in the subrepo because the predicate would match
in one of the replaced methods. Manifest doesn't know anything about subrepos,
so it needs help ignoring subrepos when complaining about bad files.
Testing that hghave does not crash when checking features
$ "$TESTDIR/hghave" --test-features 2>/dev/null