merge: display modify/delete conflict prompts in sorted order

The order is determined by manifest.diff(), which currently is not
sorted. There are currently no tests for this, but we will soon add
some that would be flaky without this patch.

mercurial/merge.py

@@ -601,7 +601,7 b' def calculateupdates(repo, wctx, mctx, a'
         repo.ui.note(_('end of auction\n\n'))
 
     # Prompt and create actions. TODO: Move this towards resolve phase.
-    for f, args, msg in actions['cd']:
+    for f, args, msg in sorted(actions['cd']):
         if f in ancestors[0] and not wctx[f].cmp(ancestors[0][f]):
             # local did change but ended up with same content
             actions['r'].append((f, None, "prompt same"))
@@ -614,7 +614,7 b' def calculateupdates(repo, wctx, mctx, a'
             actions['a'].append((f, None, "prompt keep"))
     del actions['cd'][:]
 
-    for f, args, msg in actions['dc']:
+    for f, args, msg in sorted(actions['dc']):
         flags, = args
         if f in ancestors[0] and not mctx[f].cmp(ancestors[0][f]):
             # remote did change but ended up with same content