# HG changeset patch
# User Vadim Gelfer <vadim.gelfer@gmail.com>
# Date 1140028815 28800
# Node ID ace6d26f78f14df31f579f16be17549c2f5177a9
# Parent  9b92b71d5dd7edc2a02f9d33a7bb70adb0f91413# Parent  fde8fb2cbeded49d0021287fda8eab1de734d308
merge with crew.


diff --git a/mercurial/mdiff.py b/mercurial/mdiff.py
--- a/mercurial/mdiff.py
+++ b/mercurial/mdiff.py
@@ -18,16 +18,22 @@ def unidiff(a, ad, b, bd, fn, r=None, te
 
     if not text and (util.binary(a) or util.binary(b)):
         l = ['Binary file %s has changed\n' % fn]
-    elif a == None:
+    elif not a:
         b = b.splitlines(1)
-        l1 = "--- %s\t%s\n" % ("/dev/null", epoch)
+        if a is None:
+            l1 = "--- %s\t%s\n" % ("/dev/null", epoch)
+        else:
+            l1 = "--- %s\t%s\n" % ("a/" + fn, ad)
         l2 = "+++ %s\t%s\n" % ("b/" + fn, bd)
         l3 = "@@ -0,0 +1,%d @@\n" % len(b)
         l = [l1, l2, l3] + ["+" + e for e in b]
-    elif b == None:
+    elif not b:
         a = a.splitlines(1)
         l1 = "--- %s\t%s\n" % ("a/" + fn, ad)
-        l2 = "+++ %s\t%s\n" % ("/dev/null", epoch)
+        if b is None:
+            l2 = "+++ %s\t%s\n" % ("/dev/null", epoch)
+        else:
+            l2 = "+++ %s\t%s\n" % ("b/" + fn, bd)
         l3 = "@@ -1,%d +0,0 @@\n" % len(a)
         l = [l1, l2, l3] + ["-" + e for e in a]
     else:
diff --git a/tests/test-diffdir b/tests/test-diffdir
--- a/tests/test-diffdir
+++ b/tests/test-diffdir
@@ -12,3 +12,7 @@ hg diff | sed -e "s/\(+++ [a-zA-Z0-9_/.-
 
 hg diff -r tip | sed -e "s/\(+++ [a-zA-Z0-9_/.-]*\).*/\1/" \
                      -e "s/\(--- [a-zA-Z0-9_/.-]*\).*/\1/"
+
+echo foo > a
+hg diff | sed -e "s/\(+++ [a-zA-Z0-9_/.-]*\).*/\1/" \
+              -e "s/\(--- [a-zA-Z0-9_/.-]*\).*/\1/"
diff --git a/tests/test-diffdir.out b/tests/test-diffdir.out
--- a/tests/test-diffdir.out
+++ b/tests/test-diffdir.out
@@ -8,3 +8,13 @@ diff -r 3903775176ed b
 +++ b/b
 @@ -0,0 +1,1 @@
 +123
+diff -r 3903775176ed a
+--- a/a
++++ b/a
+@@ -0,0 +1,1 @@
++foo
+diff -r 3903775176ed b
+--- /dev/null
++++ b/b
+@@ -0,0 +1,1 @@
++123