This can happen when a file with flags is removed or deleted in the working
directory and also not present in m2. The obvious solution is to add a
__delitem__ override to manifestdict that removes the file from flags if
necessary, but that has a significant performance cost in some cases, e.g.
hg status --rev rev1 --rev rev2 <file>.
Many tests didn't change back from subdirectories at the end of the tests ...
and they don't have to. The missing 'cd ..' could always be added when another
test case is added to the test file.
This change do that tests (99.5%) consistently end up in $TESTDIR where they
started, thus making it simpler to extend them or move them around.
