rewriteutil: replace "null changeset" by "the null revision" in error message

The evolve extension uses "the null revision" and we seem to use that
term much more frequently in core too.

Differential Revision: https://phab.mercurial-scm.org/D10514

mercurial/rewriteutil.py

@@ -34,7 +34,7 b" def precheck(repo, revs, action=b'rewrit"
     Make sure this function is called after taking the lock.
     """
     if nullrev in revs:
-        msg = _(b"cannot %s null changeset") % action
+        msg = _(b"cannot %s the null revision") % action
         hint = _(b"no changeset checked out")
         raise error.InputError(msg, hint=hint)
 

tests/test-uncommit.t

@@ -51,7 +51,7 b' Help for uncommit'
 Uncommit with no commits should fail
 
   $ hg uncommit
-  abort: cannot uncommit null changeset
+  abort: cannot uncommit the null revision
   (no changeset checked out)
   [10]