merge: collect checking for unknown files at end of manifestmerge()

The 'c' and 'dc' actions include creating a file on disk and we need
to check that no conflicting file exists unless force=True. Move two
of the calls to _checkunknownfile() to a single place at the end of
manifestmerge(). This removes some of the reading of filelogs from the
heart of manifestmerge() and collects it in one place close to where
its output (entries in the 'aborts' list) is used.

Note that this removes the unnecessary call to _checkunknownfile()
when force=True in one of the code paths.

mercurial/merge.py

@@ -401,7 +401,6 b' def manifestmerge(repo, wctx, p2, pa, br'
                 m1['.hgsubstate'] += '+'
                 break
 
-    aborts = []
     # Compare manifests
     diff = m1.diff(m2)
 
@@ -488,8 +487,7 b' def manifestmerge(repo, wctx, p2, pa, br'
                 # following table:
                 #
                 # force  branchmerge  different  |  action
-                #   n         *           n      |   create
-                #   n         *           y      |   abort
+                #   n         *           *      |   create
                 #   y         n           *      |   create
                 #   y         y           n      |   create
                 #   y         y           y      |   merge
@@ -497,10 +495,6 b' def manifestmerge(repo, wctx, p2, pa, br'
                 # Checking whether the files are different is expensive, so we
                 # don't do that when we can avoid it.
                 if not force:
-                    different = _checkunknownfile(repo, wctx, p2, f)
-                    if different:
-                        aborts.append((f, "ud"))
-                    else:
                         actions[f] = ('c', (fl2,), "remote created")
                 elif not branchmerge:
                     actions[f] = ('c', (fl2,), "remote created")
@@ -512,15 +506,18 b' def manifestmerge(repo, wctx, p2, pa, br'
                     else:
                         actions[f] = ('g', (fl2,), "remote created")
             elif n2 != ma[f]:
-                different = _checkunknownfile(repo, wctx, p2, f)
-                if not force and different:
-                    aborts.append((f, 'ud'))
-                else:
                     if acceptremote:
                         actions[f] = ('c', (fl2,), "remote recreating")
                     else:
                         actions[f] = ('dc', (fl2,), "prompt deleted/changed")
 
+    aborts = []
+    if not force:
+        for f, (m, args, msg) in actions.iteritems():
+            if m in ('c', 'dc'):
+                if _checkunknownfile(repo, wctx, p2, f):
+                    aborts.append((f, "ud"))
+
     for f, m in sorted(aborts):
         if m == 'ud':
             repo.ui.warn(_("%s: untracked file differs\n") % f)