logcmdutil: let getlinerangerevs() return "revs" as a smartset

This makes it consistent in "hg log" command where 'revs' can come from
logcmdutil.getrevs() as a smartset or from getlinerangerevs(),
previously as a list. This will help type hinting as noticed in
https://phab.mercurial-scm.org/D7377.

mercurial/logcmdutil.py

@@ -968,7 +968,7 b' def getlinerangerevs(repo, userrevs, opt'
     differ = changesetdiffer()
     differ._makefilematcher = filematcher
     differ._makehunksfilter = hunksfilter
-    return revs, differ
+    return smartset.baseset(revs), differ
 
 
 def _graphnodeformatter(ui, displayer):