merge: drop underscore prefix from _checkunknown()

The method has been called from commands.py since 3eab42088be4
(update: just merge unknown file collisions, 2012-02-09), so drop the
underscore prefix that suggests that it's private.

hgext/largefiles/overrides.py

@@ -372,7 +372,7 b' def overrideupdate(orig, ui, repo, *pats'
         wlock.release()
 
 # Before starting the manifest merge, merge.updates will call
-# _checkunknown to check if there are any files in the merged-in
+# checkunknown to check if there are any files in the merged-in
 # changeset that collide with unknown files in the working copy.
 #
 # The largefiles are seen as unknown, so this prevents us from merging

mercurial/commands.py

@@ -6184,7 +6184,7 b' def update(ui, repo, node=None, rev=None'
             raise util.Abort(_("uncommitted changes"))
         if rev is None:
             rev = repo[repo[None].branch()].rev()
-        mergemod._checkunknown(repo, repo[None], repo[rev])
+        mergemod.checkunknown(repo, repo[None], repo[rev])
 
     repo.ui.setconfig('ui', 'forcemerge', tool, 'update')
 

mercurial/merge.py

@@ -304,7 +304,7 b' def _checkunknownfile(repo, wctx, mctx, '
         and repo.dirstate.normalize(f) not in repo.dirstate
         and mctx[f].cmp(wctx[f]))
 
-def _checkunknown(repo, wctx, mctx):
+def checkunknown(repo, wctx, mctx):
     "check for collisions between unknown files and files in mctx"
 
     error = False