revert: handle subrepos missing in the given --rev
The list of subrepos to revert is currently based on the given --rev, so there
is currently no way for this to fail. Using the --rev context is wrong though,
because if the subrepo doesn't exist in --rev, it is skipped, so it won't be
changed. This change makes it so that the revert aborts, which is what happens
if a plain file is reverted to -1. Finding matches based on --rev is also
inconsistent with evaluating files against the working directory (
5b85a5bc5bbb).
This change is made now, so as to not cause breakage when the context is
switched in an upcoming patch.
Testing that hghave does not crash when checking features
$ "$TESTDIR/hghave" --test-features 2>/dev/null