diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -2399,7 +2399,7 @@
     ('l', 'files-with-matches', None,
      _('print only filenames and revisions that match')),
     ('n', 'line-number', None, _('print matching line numbers')),
-    ('r', 'rev', [],
+    ('r', 'rev', ["wdir()"],
      _('only search files changed within revision range'), _('REV')),
     ('', 'allfiles', False,
      _('include all files in the changeset while grepping (EXPERIMENTAL)')),
@@ -2431,6 +2431,10 @@
     Returns 0 if a match is found, 1 otherwise.
     """
     opts = pycompat.byteskwargs(opts)
+
+    if len(opts.get('rev')) ==1:
+        opts['allfiles'] = True
+
     reflags = re.M
     if opts.get('ignore_case'):
         reflags |= re.I