merge: remove emptyactions() and use collections.defaultdict(list) instead

emptyactions() used to return a dict which was populated and passed into
applyupdates(). However, with recent changes, we no longer pass a plain dict,
instead we pass the mergeresult object.

There was only one usage of emptyactions and that too inside mergeresult object.
That usage is replaced with collections.defaultdict(list) instead.

Not sure why we were not using collections.defaultdict(list) from the beginning.

Differential Revision: https://phab.mercurial-scm.org/D8903

hgext/largefiles/overrides.py

@@ -497,14 +497,6 b' def overridedebugstate(orig, ui, repo, *'
         orig(ui, repo, *pats, **opts)
 
 
-# Register the MERGE_ACTION_LARGEFILE_MARK_REMOVED in emptyactions() return type
[e-mail](merge, b'emptyactions')
-def overrideemptyactions(origfn):
-    ret = origfn()
-    ret[MERGE_ACTION_LARGEFILE_MARK_REMOVED] = []
-    return ret
-
-
 # Before starting the manifest merge, merge.updates will call
 # _checkunknownfile to check if there are any files in the merged-in
 # changeset that collide with unknown files in the working copy.

mercurial/merge.py

@@ -687,7 +687,7 b' class mergeresult(object):'
     def actionsdict(self):
         """ returns a dictionary of actions to be perfomed with action as key
         and a list of files and related arguments as values """
-        res = emptyactions()
+        res = collections.defaultdict(list)
         for a, d in pycompat.iteritems(self._actionmapping):
             for f, (args, msg) in pycompat.iteritems(d):
                 res[a].append((f, args, msg))
@@ -1338,29 +1338,6 b' class updateresult(object):'
         )
 
 
-def emptyactions():
-    """create an actions dict, to be populated and passed to applyupdates()"""
-    return {
-        m: []
-        for m in (
-            mergestatemod.ACTION_ADD,
-            mergestatemod.ACTION_ADD_MODIFIED,
-            mergestatemod.ACTION_FORGET,
-            mergestatemod.ACTION_GET,
-            mergestatemod.ACTION_CHANGED_DELETED,
-            mergestatemod.ACTION_DELETED_CHANGED,
-            mergestatemod.ACTION_REMOVE,
-            mergestatemod.ACTION_DIR_RENAME_MOVE_LOCAL,
-            mergestatemod.ACTION_LOCAL_DIR_RENAME_GET,
-            mergestatemod.ACTION_MERGE,
-            mergestatemod.ACTION_EXEC,
-            mergestatemod.ACTION_KEEP,
-            mergestatemod.ACTION_PATH_CONFLICT,
-            mergestatemod.ACTION_PATH_CONFLICT_RESOLVE,
-        )
-    }
-
-
 def applyupdates(
     repo,
     mresult,