context: add workingcommitctx for exact context to be committed

Before this patch, "workingctx" is also used for the context to be
committed. But "workingctx" works incorrectly in some cases.

For example, even when only some of changed files in the working
directory are committed, "status()" on "workingctx" object for
committing recognizes files not to be committed as changed, too.

As the preparation for fixing these issues, this patch chooses adding
new class "workingcommitctx" for exact context to be committed,
because switching by the flag (like "self._fixedstatus" or so) in some
code paths of "workingctx" is less readable and maintenancable.

mercurial/context.py

@@ -1622,6 +1622,18 b' class workingfilectx(committablefilectx)'
         """wraps repo.wwrite"""
         self._repo.wwrite(self._path, data, flags)
 
+class workingcommitctx(workingctx):
+    """A workingcommitctx object makes access to data related to
+    the revision being committed convenient.
+
+    This hides changes in the working directory, if they aren't
+    committed in this context.
+    """
+    def __init__(self, repo, changes,
+                 text="", user=None, date=None, extra=None):
+        super(workingctx, self).__init__(repo, text, user, date, extra,
+                                         changes)
+
 class memctx(committablectx):
     """Use memctx to perform in-memory commits via localrepo.commitctx().
 

mercurial/localrepo.py

@@ -1343,7 +1343,8 b' class localrepository(object):'
                     elif f not in self.dirstate:
                         fail(f, _("file not tracked!"))
 
-            cctx = context.workingctx(self, text, user, date, extra, status)
+            cctx = context.workingcommitctx(self, status,
+                                            text, user, date, extra)
 
             if (not force and not extra.get("close") and not merge
                 and not cctx.files()