merge: consider the file merged when using :merge-{local,other}...
merge: consider the file merged when using :merge-{local,other}
Returning `None` from `simplemerge()` means that the caller interprets
it as "no merge was necessary (because two sides matched)". See
6217040b2780 and issue2680 for some background. However,
`simplemerge()` shouldn't even get called in such scenarios, and
returning `None` means that the file is not considered merged, even
though the contents actually were. See the affected test cases.
Differential Revision:
https://phab.mercurial-scm.org/D11999
