rhg: fallback when encountering ellipsis revisions Ellipsis revisions are still experimental and buggy in non-trivial histories. We currently have no plans to improve this situation nor to add support for ellipsis revisions in `rhg`. Falling back should be done carefully (since we may have already done some work that is visible to the user), but in this case it's highly unlikely that we're doing anything useful with a repo with ellipsis revisions, so this should be strictly better, also since the error message is more explicit.

dirstate-v2: hash the source of the ignore patterns as well Fixes the test introduced in the last changeset. This caused the hash to change, which means that the check in the test had to be adapted. Since this hash is only done as a caching mechanism, invalidation does not pose any backwards compatibility issues.

dirstate-v2: add test that shows a collision in ignore patterns hash This hash is used for optimizing dirstate `status`. We demonstrate that the hash is incorrectly ignoring the changes to the semantics of the ignore files just because the contents (but not their source) haven't changed. This is fixed in the next changeset.

testlib: add `--raw-sha1` option to `f` This will be used in the patch fixing the ignore hash collision in dirstate-v2 to check the behavior of the new hashing function.

rust-status: save new dircache even if just invalidated There was a functional race between invalidating the cache (not acted upon until the end of the status algorithm) and populating the new cache (which relies upon an up-to-date version of the cache). We simply inform the cache populating function that we've just invalidated the cache for this particular directory since the information is present in the same scope.

rust-status: fix typos and add docstrings to dircache related fields