filemerge: when merge tool uses $output, don't leave markers in $local
As explained in the previous patch, we incorrectly leave conflict
markers in both `$local` and `$output` since D12190. I don't
understand why it broke but the fix is simple and clear after all the
recent refactoring.
Differential Revision: https://phab.mercurial-scm.org/D12379
$ hg init
$ echo a > a
$ hg ci -Ama
adding a
$ hg an a
0: a
$ hg --config ui.strict=False an a
0: a
$ echo "[ui]" >> $HGRCPATH
$ echo "strict=True" >> $HGRCPATH
$ hg an a
hg: unknown command 'an'
(use 'hg help' for a list of commands)
[10]
$ hg annotate a
0: a
should succeed - up is an alias, not an abbreviation
$ hg up
0 files updated, 0 files merged, 0 files removed, 0 files unresolved