use translation

resource/locales/en_US/translation.json

@@ -333,7 +333,9 @@
     "comparing_target": "Target",
     "comparing_revisions": "Comparing the difference",
     "compare_latest":"Compare latest revision",
-    "compare_previous":"Compare previous revision"
+    "compare_previous":"Compare previous revision",
+    "no_diff":"No diff"
+
   },
   "modal_rename": {
     "label": {

resource/locales/ja_JP/translation.json

@@ -335,7 +335,8 @@
     "comparing_target": "ターゲット",
     "comparing_revisions": "差分を比較する",
     "compare_latest":"最新と比較",
-    "compare_previous":"1つ前のバージョンと比較"
+    "compare_previous":"1つ前のバージョンと比較",
+    "no_diff":"差分はありません"
   },
   "modal_rename": {
     "label": {

resource/locales/zh_CN/translation.json

@@ -314,7 +314,9 @@
     "comparing_target": "目标",
     "comparing_revisions": "比较两者的区别",
     "compare_latest":"比較最新版本",
-    "compare_previous":"比較以前的版本"
+    "compare_previous":"比較以前的版本",
+    "no_diff":"没有区别"
+
   },
 	"modal_rename": {
 		"label": {

src/client/js/components/RevisionComparer/RevisionComparer.jsx

@@ -85,7 +85,7 @@ const RevisionComparer = (props) => {
       </div>
 
       <div className="revision-compare-outer">
-        {sourceRevision === targetRevision ? 'no diff' : (
+        {sourceRevision === targetRevision ? t('page_history.no_diff') : (
           <RevisionDiff
             revisionDiffOpened
             previousRevision={sourceRevision}