--- a/hgext3rd/topic/__init__.py	Fri Jul 07 01:01:01 2017 +0200
+++ b/hgext3rd/topic/__init__.py	Thu Jul 06 03:56:36 2017 +0530
@@ -294,7 +294,24 @@
         ('l', 'list', False, 'show the stack of changeset in the topic'),
     ] + commands.formatteropts)
 def topics(ui, repo, topic='', clear=False, rev=None, list=False, **opts):
-    """View current topic, set current topic, or see all topics.
+    """View current topic, set current topic, change topic for a set of revisions, or see all topics.
+
+    Clear topic on existing topiced revisions:
+        `hg topic --rev <related revset> --clear`
+
+    Change topic on some revisions:
+        `hg topic <newtopicname> --rev <related revset>`
+
+    Clear current topic:
+        `hg topic --clear`
+
+    Set current topic:
+        `hg topic <topicname>`
+
+    List of topics:
+        `hg topics`
+
+    The active topic (if any) will be prepended with a "*".
 
     The --verbose version of this command display various information on the state of each topic."""
     if list:

--- a/tests/test-topic.t	Fri Jul 07 01:01:01 2017 +0200
+++ b/tests/test-topic.t	Thu Jul 06 03:56:36 2017 +0530
@@ -15,7 +15,25 @@
   $ hg help topics
   hg topics [TOPIC]
   
-  View current topic, set current topic, or see all topics.
+  View current topic, set current topic, change topic for a set of revisions, or
+  see all topics.
+  
+      Clear topic on existing topiced revisions:
+          'hg topic --rev <related revset> --clear'
+  
+      Change topic on some revisions:
+          'hg topic <newtopicname> --rev <related revset>'
+  
+      Clear current topic:
+          'hg topic --clear'
+  
+      Set current topic:
+          'hg topic <topicname>'
+  
+      List of topics:
+          'hg topics'
+  
+      The active topic (if any) will be prepended with a "*".
   
       The --verbose version of this command display various information on the
       state of each topic.