Fix local file changes being ignored after non-branch merge
Bug introduced in eea96285cbf9
Spotted by TAH
+ hg init
+ echo nothing
+ hg add a
+ hg commit -m ancestor -d '0 0'
+ echo something
+ hg commit -m branch1 -d '0 0'
+ hg co 0
+ echo 'something else'
+ hg commit -m branch2 -d '0 0'
+ export HGMERGE=merge
+ HGMERGE=merge
+ hg up -m 1
merge: warning: conflicts during merge
merging a
merging a failed!
+ hg id
32e80765d7fe+75234512624c+ tip
+ grep -Ev '>>>|<<<' a
something else
=======
something
+ hg status
M a
? .out