--- a/CHANGELOG	Mon Jan 15 18:41:29 2018 +0100
+++ b/CHANGELOG	Wed Dec 27 04:09:50 2017 +0530
@@ -19,6 +19,7 @@
   * evolve: changes to the on disk format for interrupted evolve
   * evolve: preserve phase information with --continue (issue5720)
   * evolve: --continue now properly reports merges as evolve
+  * commit: suggest using topic on new heads
 
 topic (0.7.1)
 

--- a/hgext3rd/topic/topicmap.py	Mon Jan 15 18:41:29 2018 +0100
+++ b/hgext3rd/topic/topicmap.py	Wed Dec 27 04:09:50 2017 +0530
@@ -1,6 +1,7 @@
 import contextlib
 import hashlib
 
+from mercurial.i18n import _
 from mercurial.node import nullid
 from mercurial import (
     branchmap,
@@ -94,7 +95,23 @@
     if ctx.topic() and ctx.branch() == branch:
         subbranch = "%s:%s" % (branch, ctx.topic())
         bheads = repo.branchheads("%s:%s" % (subbranch, ctx.topic()))
-    return orig(repo, node, branch, bheads=bheads, opts=opts)
+
+    ret = orig(repo, node, branch, bheads=bheads, opts=opts)
+
+    # logic copy-pasted from cmdutil.commitstatus()
+    if opts is None:
+        opts = {}
+    ctx = repo[node]
+    if ctx.topic():
+        return ret
+    parents = ctx.parents()
+
+    if (not opts.get('amend') and bheads and node not in bheads and not
+        [x for x in parents if x.node() in bheads and x.branch() == branch]):
+        repo.ui.status(_("(consider using topic for lightweight branches."
+                         " See 'hg help topic')\n"))
+
+    return ret
 
 def _wrapbmcache(ui):
     class topiccache(_topiccache, branchmap.branchcache):

--- a/tests/test-minitopic.t	Mon Jan 15 18:41:29 2018 +0100
+++ b/tests/test-minitopic.t	Wed Dec 27 04:09:50 2017 +0530
@@ -81,6 +81,7 @@
   0 files updated, 0 files merged, 1 files removed, 0 files unresolved
   $ mkcommit c_C0
   created new head
+  (consider using topic for lightweight branches. See 'hg help topic')
   $ hg push enabled
   pushing to http://localhost:$HGPORT/
   searching for changes

--- a/tests/test-stack-branch.t	Mon Jan 15 18:41:29 2018 +0100
+++ b/tests/test-stack-branch.t	Wed Dec 27 04:09:50 2017 +0530
@@ -181,6 +181,7 @@
   $ hg add ggg
   $ hg commit -m c_g
   created new head
+  (consider using topic for lightweight branches. See 'hg help topic')
   $ echo aaa > hhh
   $ hg add hhh
   $ hg commit -m c_h

--- a/tests/test-topic-flow-publish-bare.t	Mon Jan 15 18:41:29 2018 +0100
+++ b/tests/test-topic-flow-publish-bare.t	Wed Dec 27 04:09:50 2017 +0530
@@ -52,10 +52,12 @@
   0 files updated, 0 files merged, 1 files removed, 0 files unresolved
   $ mkcommit c_dC0
   created new head
+  (consider using topic for lightweight branches. See 'hg help topic')
   $ hg update 'desc("c_dA0")'
   0 files updated, 0 files merged, 1 files removed, 0 files unresolved
   $ mkcommit c_dD0
   created new head
+  (consider using topic for lightweight branches. See 'hg help topic')
   $ hg push -f
   pushing to $TESTTMP/bare-branch-server
   searching for changes

--- a/tests/test-topic-flow-single-head.t	Mon Jan 15 18:41:29 2018 +0100
+++ b/tests/test-topic-flow-single-head.t	Wed Dec 27 04:09:50 2017 +0530
@@ -63,6 +63,7 @@
   1 files updated, 0 files merged, 1 files removed, 0 files unresolved
   $ mkcommit c_dD0
   created new head
+  (consider using topic for lightweight branches. See 'hg help topic')
   $ hg push -f
   pushing to $TESTTMP/single-head-server
   searching for changes

--- a/tests/test-topic-fold.t	Mon Jan 15 18:41:29 2018 +0100
+++ b/tests/test-topic-fold.t	Wed Dec 27 04:09:50 2017 +0530
@@ -78,6 +78,7 @@
   $ hg topic --clear
   $ mkcommit feature3
   created new head
+  (consider using topic for lightweight branches. See 'hg help topic')
   $ hg topic myotherfeature
   marked working directory as topic: myotherfeature
   $ mkcommit feature4

--- a/tests/test-topic-push-concurrent-on.t	Mon Jan 15 18:41:29 2018 +0100
+++ b/tests/test-topic-push-concurrent-on.t	Wed Dec 27 04:09:50 2017 +0530
@@ -58,6 +58,7 @@
   $ hg add ccc
   $ hg commit -m 'CC'
   created new head
+  (consider using topic for lightweight branches. See 'hg help topic')
   $ hg outgoing -G
   comparing with $TESTTMP/main (glob)
   searching for changes
@@ -313,6 +314,7 @@
   $ hg add ggg
   $ hg commit -m 'CG'
   created new head
+  (consider using topic for lightweight branches. See 'hg help topic')
   $ hg up 'desc(CF)'
   switching to topic babar
   2 files updated, 0 files merged, 1 files removed, 0 files unresolved

--- a/tests/test-topic-push.t	Mon Jan 15 18:41:29 2018 +0100
+++ b/tests/test-topic-push.t	Wed Dec 27 04:09:50 2017 +0530
@@ -54,6 +54,7 @@
   $ hg add ccc
   $ hg commit -m 'CC'
   created new head
+  (consider using topic for lightweight branches. See 'hg help topic')
   $ hg outgoing -G
   comparing with $TESTTMP/main (glob)
   searching for changes
@@ -364,6 +365,7 @@
   $ hg add ggg
   $ hg commit -m 'CG'
   created new head
+  (consider using topic for lightweight branches. See 'hg help topic')
   $ hg up 'desc(CF)'
   switching to topic babar
   2 files updated, 0 files merged, 1 files removed, 0 files unresolved

--- a/tests/test-topic-rebase.t	Mon Jan 15 18:41:29 2018 +0100
+++ b/tests/test-topic-rebase.t	Wed Dec 27 04:09:50 2017 +0530
@@ -101,6 +101,7 @@
   $ echo "A" > file
   $ hg commit -A -m "default2" file
   created new head
+  (consider using topic for lightweight branches. See 'hg help topic')
 
 Update the common file in a topic
   $ hg topic myotherfeature

--- a/tests/test-topic-stack-data.t	Mon Jan 15 18:41:29 2018 +0100
+++ b/tests/test-topic-stack-data.t	Wed Dec 27 04:09:50 2017 +0530
@@ -44,6 +44,7 @@
   0 files updated, 0 files merged, 1 files removed, 0 files unresolved
   $ mkcommit lake_c
   created new head
+  (consider using topic for lightweight branches. See 'hg help topic')
 
 
 Add some topics

--- a/tests/test-topic.t	Mon Jan 15 18:41:29 2018 +0100
+++ b/tests/test-topic.t	Wed Dec 27 04:09:50 2017 +0530
@@ -612,6 +612,7 @@
   $ echo fran? >> beta
   $ hg ci -m 'fran?'
   created new head
+  (consider using topic for lightweight branches. See 'hg help topic')
   $ hg log -Gr 'draft()'
   @  changeset:   10:4073470c35e1
   |  tag:         tip