hooks: invalidate the repo after the hooks Since the hooks may have changed the repository content it seems safer to invalidate it. The invalidation is "soft", the data are kept around and few work will be needed to restore them if nothing actually changed.

dirstate: try refreshing the changelog when parent are unknown See inline comment for details.

localrepo: add a `currentlock` method It mirrors he `currentwlock` function.

dirstate: add a test to highlight another changelog / dirstate race