Merge "diff: Display "(No difference)" instead of an empty diff"

diff --combined RELEASE-NOTES-1.22
index 417ecb4,86b0c2b..8ed4622
--- 1/RELEASE-NOTES-1.22
--- 2/RELEASE-NOTES-1.22
+++ b/RELEASE-NOTES-1.22
@@@ -147,6 -147,8 +147,8 @@@ production
  * Added a new method and hook, User::isEveryoneAllowed() and
    UserIsEveryoneAllowed, for use in situations where a "does everyone have this
    right?" check is used to avoid more expensive checks.
+ * Display "(No difference)" instead of an empty diff (when comparing revisions
+   in the history or when previewing changes while editing).
  
  === Bug fixes in 1.22 ===
  * Disable Special:PasswordReset when $wgEnableEmail is false. Previously one
@@@ -198,7 -200,6 +200,7 @@@
  * CSSJanus now supports rgb, hsl, rgba, and hsla color syntaxes.
  * Special:Listfiles can no longer be sorted by image name when filtering
    by user in miser mode.
 +* (bug 49074) CSSJanus: Handle values of border-radius correctly.
  
  === API changes in 1.22 ===
  * (bug 25553) The JSON output formatter now leaves forward slashes unescaped