revset: drop unnecessary calls of getall() with empty argument

If x is None, getall(repo, subset, x) == subset.

mercurial/revset.py

@@ -746,7 +746,7 b' def destination(repo, subset, x):'
     if x is not None:
         sources = getset(repo, fullreposet(repo), x)
     else:
-        sources = getall(repo, fullreposet(repo), x)
+        sources = fullreposet(repo)
 
     dests = set()
 
@@ -1347,7 +1347,7 b' def origin(repo, subset, x):'
     if x is not None:
         dests = getset(repo, fullreposet(repo), x)
     else:
-        dests = getall(repo, fullreposet(repo), x)
+        dests = fullreposet(repo)
 
     def _firstsrc(rev):
         src = _getrevsource(repo, rev)