util: make 'hg log -d --2' abort (issue2734)

mercurial/util.py

@@ -1209,6 +1209,9 b' def matchdate(date):'
             days = int(date[1:])
         except ValueError:
             raise Abort(_("invalid day spec: %s") % date[1:])
+        if days < 0:
+            raise Abort(_("%s must be nonnegative (see 'hg help dates')")
+                % date[1:])
         when = makedate()[0] - days * 3600 * 24
         return lambda x: x >= when
     elif " to " in date:

tests/test-log.t

@@ -534,6 +534,11 b' log -d "<"'
   abort: invalid day spec, use '<DATE'
   [255]
 
+Negative ranges
+  $ hg log -d "--2"
+  abort: -2 must be nonnegative (see 'hg help dates')
+  [255]
+
 
 log -p -l2 --color=always