histedit: add checkunfinished support (issue3955) The tests contain a couple corner cases where workarounds are now required. Strictly speaking, these are behavior regressions, but of an extremely obscure and marginal sort. Commits or updates in the middle of a histedit would have almost always been fairly serious user error.

rebase: add checkunfinished support (issue3955)

rebase: reorder parent check and state storage This could cause a rebase to be 'in progress' even though it aborted.

commands: add checks for unfinished operations (issue3955) commands checked: backout bisect commit graft import

update: clear any clearable unfinished operations (issue3955) Unclearable operations will cause an abort.

cmdutil: core functionality to block during multistep commands (issue3955) This adds a registration point and check functions that will allow commands to check if multistep operations like an interrupted graft or rebase are in progress before proceeding.

histedit: refuse to edit history that contains merges (issue3962)

largefiles: overridematch() should replace the file path instead of extending (issue3934)

revlog: handle hidden revs in _partialmatch (issue3979) Looking up hidden prefixes could cause a no node exception Looking up unique non-hidden prefixes could be ambiguous

fileset: handle underbar in symbols This was documented, but not implemented.