merge: delay prompts a bit and show them in (extra) sorted order

Preparing for backout of 760c0d67ce5e.

The number of prompts will for all relevant cases be significantly smaller than
the total number of files in the manifests. We can thus afford to sort the
prompts more than we can afford to sort the manifests.

mercurial/merge.py

@@ -227,6 +227,7 b' def manifestmerge(repo, p1, p2, pa, over'
                 m1['.hgsubstate'] += "+"
                 break
 
+    prompts = []
     # Compare manifests
     visit = m1.iteritems()
     if repo.ui.debugflag:
@@ -265,13 +266,7 b' def manifestmerge(repo, p1, p2, pa, over'
             act("local copied/moved to " + f2, "m", f, f2, f, False)
         elif f in ma: # clean, a different, no remote
             if n != ma[f]:
-                if repo.ui.promptchoice(
-                    _(" local changed %s which remote deleted\n"
-                      "use (c)hanged version or (d)elete?") % f,
-                    (_("&Changed"), _("&Delete")), 0):
-                    act("prompt delete", "r", f)
-                else:
-                    act("prompt keep", "a", f)
+                prompts.append((f, "cd")) # prompt changed/deleted
             elif n[20:] == "a": # added, no remote
                 act("remote deleted", "f", f)
             else:
@@ -305,12 +300,24 b' def manifestmerge(repo, p1, p2, pa, over'
             else:
                 act("remote created", "g", f, m2.flags(f))
         elif n != ma[f]:
+            prompts.append((f, "dc")) # prompt deleted/changed
+
+    for f, m in sorted(prompts):
+        if m == "cd":
+            if repo.ui.promptchoice(
+                _(" local changed %s which remote deleted\n"
+                  "use (c)hanged version or (d)elete?") % f,
+                (_("&Changed"), _("&Delete")), 0):
+                act("prompt delete", "r", f)
+            else:
+                act("prompt keep", "a", f)
+        elif m == "dc":
             if repo.ui.promptchoice(
                 _("remote changed %s which local deleted\n"
                   "use (c)hanged version or leave (d)eleted?") % f,
                 (_("&Changed"), _("&Deleted")), 0) == 0:
                 act("prompt recreating", "g", f, m2.flags(f))
-
+        else: assert False, m
     return actions
 
 def actionkey(a):

tests/test-rename-merge2.t

@@ -617,11 +617,11 b' m "um a c" "um x c" " " "10 do merg'
   resolving manifests
    overwrite: False, partial: False
    ancestor: 924404dff337, local: 0b76e65c8289+, remote: bdb19105162a
+   b: versions differ -> m
+   rev: versions differ -> m
    local changed a which remote deleted
   use (c)hanged version or (d)elete? c
    a: prompt keep -> a
-   b: versions differ -> m
-   rev: versions differ -> m
   preserving b for resolve of b
   preserving rev for resolve of rev
   updating: a 1/3 files (33.33%)