merge: rework manifestmerge to use a matcher

merge: rework manifestmerge to use a matcher

This opens the door to working slightly more closely with the manifest
type and letting it optimize out some of the diff comparisons for us,
and also makes life significantly easier for narrowhg.

--- a/mercurial/merge.py	Mon Dec 14 20:37:41 2015 -0500
+++ b/mercurial/merge.py	Mon Dec 14 20:47:22 2015 -0500
@@ -683,15 +683,17 @@
     This is currently not implemented -- it's an extension point."""
     return True
 
-def manifestmerge(repo, wctx, p2, pa, branchmerge, force, partial,
+def manifestmerge(repo, wctx, p2, pa, branchmerge, force, matcher,
                   acceptremote, followcopies):
     """
     Merge p1 and p2 with ancestor pa and generate merge action list
 
     branchmerge and force are as passed in to update
-    partial = function to filter file lists
+    matcher = matcher to filter file lists
     acceptremote = accept the incoming changes without prompting
     """
+    if matcher is not None and matcher.always():
+        matcher = None
 
     copy, movewithdir, diverge, renamedelete = {}, {}, {}, {}
 
@@ -705,7 +707,7 @@
 
     repo.ui.note(_("resolving manifests\n"))
     repo.ui.debug(" branchmerge: %s, force: %s, partial: %s\n"
-                  % (bool(branchmerge), bool(force), bool(partial)))
+                  % (bool(branchmerge), bool(force), bool(matcher)))
     repo.ui.debug(" ancestor: %s, local: %s, remote: %s\n" % (pa, wctx, p2))
 
     m1, m2, ma = wctx.manifest(), p2.manifest(), pa.manifest()
@@ -724,7 +726,7 @@
 
     actions = {}
     for f, ((n1, fl1), (n2, fl2)) in diff.iteritems():
-        if partial and not partial(f):
+        if matcher and not matcher(f):
             continue
         if n1 and n2: # file exists on both local and remote side
             if f not in ma:
@@ -844,14 +846,9 @@
 def calculateupdates(repo, wctx, mctx, ancestors, branchmerge, force,
                      acceptremote, followcopies, matcher=None):
     "Calculate the actions needed to merge mctx into wctx using ancestors"
-    if matcher is None or matcher.always():
-        partial = False
-    else:
-        partial = matcher.matchfn
-
     if len(ancestors) == 1: # default
         actions, diverge, renamedelete = manifestmerge(
-            repo, wctx, mctx, ancestors[0], branchmerge, force, partial,
+            repo, wctx, mctx, ancestors[0], branchmerge, force, matcher,
             acceptremote, followcopies)
         _checkunknownfiles(repo, wctx, mctx, force, actions)
 
@@ -866,7 +863,7 @@
         for ancestor in ancestors:
             repo.ui.note(_('\ncalculating bids for ancestor %s\n') % ancestor)
             actions, diverge1, renamedelete1 = manifestmerge(
-                repo, wctx, mctx, ancestor, branchmerge, force, partial,
+                repo, wctx, mctx, ancestor, branchmerge, force, matcher,
                 acceptremote, followcopies)
             _checkunknownfiles(repo, wctx, mctx, force, actions)