diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -2544,6 +2544,10 @@
     if opts.get('print0'):
         sep = eol = '\0'
 
+    if not opts.get('rev') and not diff:
+        opts.get('rev').append("wdir()")
+        opts['allfiles'] = True
+
     getfile = util.lrucachefunc(repo.file)
 
     def matchlines(body):
diff --git a/tests/test-grep.t b/tests/test-grep.t
--- a/tests/test-grep.t
+++ b/tests/test-grep.t
@@ -24,65 +24,61 @@
 simple
 
   $ hg grep '.*'
-  port:4:export
-  port:4:vaportight
-  port:4:import/export
+  port:2147483647:export
+  port:2147483647:vaportight
+  port:2147483647:import/export
   $ hg grep port port
-  port:4:export
-  port:4:vaportight
-  port:4:import/export
+  [1]
 
 simple with color
 
   $ hg --config extensions.color= grep --config color.mode=ansi \
   >     --color=always port port
-  \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;32m4\x1b[0m\x1b[0;36m:\x1b[0mex\x1b[0;31;1mport\x1b[0m (esc)
-  \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;32m4\x1b[0m\x1b[0;36m:\x1b[0mva\x1b[0;31;1mport\x1b[0might (esc)
-  \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;32m4\x1b[0m\x1b[0;36m:\x1b[0mim\x1b[0;31;1mport\x1b[0m/ex\x1b[0;31;1mport\x1b[0m (esc)
+  [1]
 
 simple templated
 
   $ hg grep port \
   > -T '{file}:{rev}:{node|short}:{texts % "{if(matched, text|upper, text)}"}\n'
-  port:4:914fa752cdea:exPORT
-  port:4:914fa752cdea:vaPORTight
-  port:4:914fa752cdea:imPORT/exPORT
+  port:2147483647:ffffffffffff:exPORT
+  port:2147483647:ffffffffffff:vaPORTight
+  port:2147483647:ffffffffffff:imPORT/exPORT
 
   $ hg grep port -T '{file}:{rev}:{texts}\n'
-  port:4:export
-  port:4:vaportight
-  port:4:import/export
+  port:2147483647:export
+  port:2147483647:vaportight
+  port:2147483647:import/export
 
 simple JSON (no "change" field)
 
   $ hg grep -Tjson port
   [
    {
-    "date": [4, 0],
+    "date": [0, 0],
     "file": "port",
     "line_number": 1,
-    "node": "914fa752cdea87777ac1a8d5c858b0c736218f6c",
-    "rev": 4,
+    "node": "ffffffffffffffffffffffffffffffffffffffff",
+    "rev": 2147483647,
     "texts": [{"matched": false, "text": "ex"}, {"matched": true, "text": "port"}],
-    "user": "spam"
+    "user": "test"
    },
    {
-    "date": [4, 0],
+    "date": [0, 0],
     "file": "port",
     "line_number": 2,
-    "node": "914fa752cdea87777ac1a8d5c858b0c736218f6c",
-    "rev": 4,
+    "node": "ffffffffffffffffffffffffffffffffffffffff",
+    "rev": 2147483647,
     "texts": [{"matched": false, "text": "va"}, {"matched": true, "text": "port"}, {"matched": false, "text": "ight"}],
-    "user": "spam"
+    "user": "test"
    },
    {
-    "date": [4, 0],
+    "date": [0, 0],
     "file": "port",
     "line_number": 3,
-    "node": "914fa752cdea87777ac1a8d5c858b0c736218f6c",
-    "rev": 4,
+    "node": "ffffffffffffffffffffffffffffffffffffffff",
+    "rev": 2147483647,
     "texts": [{"matched": false, "text": "im"}, {"matched": true, "text": "port"}, {"matched": false, "text": "/ex"}, {"matched": true, "text": "port"}],
-    "user": "spam"
+    "user": "test"
    }
   ]
 
@@ -91,12 +87,12 @@
   $ hg grep -Tjson -l port
   [
    {
-    "date": [4, 0],
+    "date": [0, 0],
     "file": "port",
     "line_number": 1,
-    "node": "914fa752cdea87777ac1a8d5c858b0c736218f6c",
-    "rev": 4,
-    "user": "spam"
+    "node": "ffffffffffffffffffffffffffffffffffffffff",
+    "rev": 2147483647,
+    "user": "test"
    }
   ]
 
@@ -212,9 +208,9 @@
 other
 
   $ hg grep -l port port
-  port:4
+  [1]
   $ hg grep import port
-  port:4:import/export
+  [1]
 
   $ hg cp port port2
   $ hg commit -m 4 -u spam -d '5 0'
@@ -222,8 +218,7 @@
 follow
 
   $ hg grep --traceback -f 'import\n\Z' port2
-  port:0:import
-  
+  [1]
   $ echo deport >> port2
   $ hg commit -m 5 -u eggs -d '6 0'
   $ hg grep -f --all -nu port port2
@@ -275,7 +270,7 @@
   $ echo blue >> color
   $ hg ci -m 3
   $ hg grep orange
-  color:3:orange
+  color:2147483647:orange
   $ hg grep --all orange
   color:3:+:orange
   color:2:-:orange
@@ -289,9 +284,9 @@
 test substring match: '^' should only match at the beginning
 
   $ hg grep '^.' --config extensions.color= --color debug
-  [grep.filename|color][grep.sep|:][grep.rev|3][grep.sep|:][grep.match|b]lack
-  [grep.filename|color][grep.sep|:][grep.rev|3][grep.sep|:][grep.match|o]range
-  [grep.filename|color][grep.sep|:][grep.rev|3][grep.sep|:][grep.match|b]lue
+  [grep.filename|color][grep.sep|:][grep.rev|2147483647][grep.sep|:][grep.match|b]lack
+  [grep.filename|color][grep.sep|:][grep.rev|2147483647][grep.sep|:][grep.match|o]range
+  [grep.filename|color][grep.sep|:][grep.rev|2147483647][grep.sep|:][grep.match|b]lue
 
 match in last "line" without newline
 
@@ -299,7 +294,7 @@
   $ hg ci -Amnoeol
   adding noeol
   $ hg grep loop
-  noeol:4:no infinite loop
+  noeol:2147483647:no infinite loop
 
   $ cd ..
 
@@ -316,8 +311,7 @@
   $ hg rename color colour
   $ hg ci -Am rename
   $ hg grep octarine
-  colour:1:octarine
-  color:0:octarine
+  colour:2147483647:octarine
 
 Used to crash here