overlayworkingctx: add _auditconflicts to write()
Alas, part of Mercurial's conflict detection (for file<->folder conflicts,
for example) depends on the filesystem. We don't have the filesystem with IMM,
so we have to run these checks ourselves.
Differential Revision: https://phab.mercurial-scm.org/D1241
$ hg init
$ touch unknown
$ touch a
$ hg add a
$ hg ci -m "1"
$ touch b
$ hg add b
$ hg ci -m "2"
Should show unknown
$ hg status
? unknown
$ hg revert -r 0 --all
removing b
Should show unknown and b removed
$ hg status
R b
? unknown
Should show a and unknown
$ ls
a
unknown