graft: fix --base value to be saved in state file
'True' just works because it is treated as an integer revision '1' and
only the truthiness of the basectx is important. If multiple source revisions
were supported with --base, the resumed graft operation would go wrong.
Pierre-Yves David <pierre-yves.david@octobus.net> [Sat, 16 May 2020 20:38:53 +0200] rev 44914
flags: also test merge with executable bit removed
This might catch more bug in the future.
Differential Revision: https://phab.mercurial-scm.org/D8536