--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -32,19 +32,24 @@ def relpath(repo, args):
         return [ util.pconvert(os.path.normpath(os.path.join(p, x))) for x in args ]
     return args
 
-def dodiff(ui, repo, path, files = None, node1 = None, node2 = None):
+def dodiff(ui, repo, files = None, node1 = None, node2 = None):
     def date(c):
         return time.asctime(time.gmtime(float(c[2].split(' ')[0])))
 
+    (c, a, d, u) = repo.changes(None, node1, files)
+    if files:
+        c, a, d = map(lambda x: filterfiles(files, x), (c, a, d))
+
+    if not c and not a and not d:
+        return
+
     if node2:
         change = repo.changelog.read(node2)
         mmap2 = repo.manifest.read(change[0])
-        (c, a, d, u) = repo.changes(node1, node2)
         def read(f): return repo.file(f).read(mmap2[f])
         date2 = date(change)
     else:
         date2 = time.asctime()
-        (c, a, d, u) = repo.changes(None, node1, path)
         if not node1:
             node1 = repo.dirstate.parents()[0]
         def read(f): return repo.wfile(f).read()
@@ -59,9 +64,6 @@ def dodiff(ui, repo, path, files = None,
     mmap = repo.manifest.read(change[0])
     date1 = date(change)
 
-    if files:
-        c, a, d = map(lambda x: filterfiles(files, x), (c, a, d))
-
     for f in c:
         to = None
         if f in mmap:
@@ -411,7 +413,7 @@ def diff(ui, repo, *files, **opts):
     else:
         files = relpath(repo, [""])
 
-    dodiff(ui, repo, os.getcwd(), files, *revs)
+    dodiff(ui, repo, files, *revs)
 
 def export(ui, repo, changeset):
     """dump the changeset header and diffs for a revision"""
@@ -428,7 +430,7 @@ def export(ui, repo, changeset):
     print change[4].rstrip()
     print
 
-    dodiff(ui, repo, "", None, prev, node)
+    dodiff(ui, repo, None, prev, node)
 
 def forget(ui, repo, file, *files):
     """don't add the specified files on the next commit"""
@@ -645,7 +647,7 @@ def status(ui, repo):
     R = removed
     ? = not tracked'''
 
-    (c, a, d, u) = repo.changes(None, None, os.getcwd())
+    (c, a, d, u) = repo.changes(None, None)
     (c, a, d, u) = map(lambda x: relfilter(repo, x), (c, a, d, u))
 
     for f in c: print "C", f

--- a/mercurial/hg.py
+++ b/mercurial/hg.py
@@ -306,6 +306,7 @@ class dirstate:
         # recursive generator of all files listed
         def walk(files):
             for f in uniq(files):
+                f = os.path.join(self.root, f)
                 if os.path.isdir(f):
                     for dir, subdirs, fl in os.walk(f):
                         d = dir[len(self.root) + 1:]
@@ -691,7 +692,7 @@ class localrepository:
         self.dirstate.update(new, "n")
         self.dirstate.forget(remove)
 
-    def changes(self, node1, node2, *files):
+    def changes(self, node1, node2, files=None):
         # changed, added, deleted, unknown
         c, a, d, u, mf1 = [], [], [], [], None