merge: branch code into {n1 and n2, n1, n2} top-level cases

There are three high-level cases that are of interest in
manifestmerge(): 1) The file exists on both sides, 2) The file exists
only on the local side, and 3) The file exists only on the remote
side. Let's make this clearer in the code.

The 'if f in copied' case will be broken up into the two applicable
branches in the next patch.

mercurial/merge.py

@@ -414,7 +414,7 b' def manifestmerge(repo, wctx, p2, pa, br'
     for f, ((n1, fl1), (n2, fl2)) in diff.iteritems():
         if partial and not partial(f):
             continue
-        if n1 and n2:
+        if n1 and n2: # file exists on both local and remote side
             if f not in ma:
                 fa = copy.get(f, None)
                 if fa is not None:
@@ -443,32 +443,35 b' def manifestmerge(repo, wctx, p2, pa, br'
                                    "versions differ"))
         elif f in copied: # files we'll deal with on m2 side
             pass
-        elif n1 and f in movewithdir: # directory rename, move local
+        elif n1: # file exists only on local side
+            if f in movewithdir: # directory rename, move local
             f2 = movewithdir[f]
             actions['dm'].append((f2, (f, fl1),
                             "remote directory rename - move from " + f))
-        elif n1 and f in copy:
+            elif f in copy:
             f2 = copy[f]
             actions['m'].append((f, (f, f2, f2, False, pa.node()),
                             "local copied/moved from " + f2))
-        elif n1 and f in ma: # clean, a different, no remote
+            elif f in ma: # clean, a different, no remote
             if n1 != ma[f]:
                 if acceptremote:
                     actions['r'].append((f, None, "remote delete"))
                 else:
-                    actions['cd'].append((f, None, "prompt changed/deleted"))
+                        actions['cd'].append((f, None,
+                                              "prompt changed/deleted"))
             elif n1[20:] == 'a':
-                # This extra 'a' is added by working copy manifest to mark the
-                # file as locally added. We should forget it instead of
+                    # This extra 'a' is added by working copy manifest to mark
+                    # the file as locally added. We should forget it instead of
                 # deleting it.
                 actions['f'].append((f, None, "remote deleted"))
             else:
                 actions['r'].append((f, None, "other deleted"))
-        elif n2 and f in movewithdir:
+        elif n2: # file exists only on remote side
+            if f in movewithdir:
             f2 = movewithdir[f]
             actions['dg'].append((f2, (f, fl2),
                             "local directory rename - get from " + f))
-        elif n2 and f in copy:
+            elif f in copy:
             f2 = copy[f]
             if f2 in m2:
                 actions['m'].append((f, (f2, f, f2, False, pa.node()),
@@ -476,7 +479,7 b' def manifestmerge(repo, wctx, p2, pa, br'
             else:
                 actions['m'].append((f, (f2, f, f2, True, pa.node()),
                                 "remote moved from " + f2))
-        elif n2 and f not in ma:
+            elif f not in ma:
             # local unknown, remote created: the logic is described by the
             # following table:
             #
@@ -500,7 +503,7 b' def manifestmerge(repo, wctx, p2, pa, br'
                     aborts.append((f, 'ud'))
                 else:
                     actions['g'].append((f, (fl2,), "remote created"))
-        elif n2 and n2 != ma[f]:
+            elif n2 != ma[f]:
             different = _checkunknownfile(repo, wctx, p2, f)
             if not force and different:
                 aborts.append((f, 'ud'))
@@ -508,7 +511,8 b' def manifestmerge(repo, wctx, p2, pa, br'
                 if acceptremote:
                     actions['g'].append((f, (fl2,), "remote recreating"))
                 else:
-                    actions['dc'].append((f, (fl2,), "prompt deleted/changed"))
+                        actions['dc'].append((f, (fl2,),
+                                              "prompt deleted/changed"))
 
     for f, m in sorted(aborts):
         if m == 'ud':