Show revert only in case it makes sense

Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/html/last-changes.html

@@ -25,7 +25,7 @@
 <td><a href="{{ c.get_translation_url }}">{{ c.get_translation_display }}</a></td>
 <td></td>
 </tr>
-{% if c.target and c.unit %}
+{% if c.can_revert %}
 <tr>
 <td colspan="4">{% format_translation c.target c.unit.translation.language %}</td>
 <td>

weblate/trans/models/changes.py

@@ -233,3 +233,15 @@ class Change(models.Model):
                 self.dictionary.language
             )
         return None
+
+    def can_revert(self):
+        return (
+            self.unit is not None and
+            self.target and
+            self.action in (
+                Change.ACTION_ACCEPT,
+                Change.ACTION_REVERT,
+                Change.ACTION_CHANGE,
+                Change.ACTION_NEW
+            )
+        )