merge: make mergeresult constructor initialize empty object

In future patches, we will be going to update mergeresult object
instead of building an actions dict and then setting it in the object.

Differential Revision: https://phab.mercurial-scm.org/D8819

mercurial/merge.py

@@ -546,7 +546,7 b' class mergeresult(object):'
     It has information about what actions need to be performed on dirstate
     mapping of divergent renames and other such cases. '''
 
-    def __init__(self, actions, diverge, renamedelete, commitinfo):
+    def __init__(self):
         """
         actions: dict of filename as keys and action related info as values
         diverge: mapping of source name -> list of dest name for
@@ -556,7 +556,12 b' class mergeresult(object):'
         commitinfo: dict containing data which should be used on commit
                     contains a filename -> info mapping
         """
+        self._actions = {}
+        self._diverge = {}
+        self._renamedelete = {}
+        self._commitinfo = {}
 
+    def updatevalues(self, actions, diverge, renamedelete, commitinfo):
         self._actions = actions
         self._diverge = diverge
         self._renamedelete = renamedelete
@@ -914,7 +919,9 b' def manifestmerge('
     renamedelete = branch_copies1.renamedelete
     renamedelete.update(branch_copies2.renamedelete)
 
-    return mergeresult(actions, diverge, renamedelete, commitinfo)
+    mresult = mergeresult()
+    mresult.updatevalues(actions, diverge, renamedelete, commitinfo)
+    return mresult
 
 
 def _resolvetrivial(repo, wctx, mctx, ancestor, actions):
@@ -965,6 +972,7 b' def calculateupdates('
     # Avoid cycle.
     from . import sparse
 
+    mresult = None
     if len(ancestors) == 1:  # default
         mresult = manifestmerge(
             repo,
@@ -1075,7 +1083,8 b' def calculateupdates('
             continue
         repo.ui.note(_(b'end of auction\n\n'))
         # TODO: think about commitinfo when bid merge is used
-        mresult = mergeresult(actions, diverge, renamedelete, {})
+        mresult = mergeresult()
+        mresult.updatevalues(actions, diverge, renamedelete, {})
 
     if wctx.rev() is None:
         fractions = _forgetremoved(wctx, mctx, branchmerge)