--- a/tests/test-topic.t	Sat Dec 22 01:29:59 2018 -0500
+++ b/tests/test-topic.t	Sun Dec 16 11:22:04 2018 +0800
@@ -823,6 +823,86 @@
 
   $ cd ..
 
+Stack relation subscript in revsets
+===================================
+
+  $ hg init more-than-one-commit-per-topic
+  $ cd more-than-one-commit-per-topic
+  $ cat > .hg/hgrc << EOF
+  > [phases]
+  > publish=false
+  > EOF
+
+  $ echo 0 > foo
+  $ hg ci -qAm 0
+  $ hg topic featureA
+  marked working directory as topic: featureA
+  $ echo 1 > foo
+  $ hg ci -qm 1
+  $ echo 2 > foo
+  $ hg ci -qm 2
+  $ echo 3 > foo
+  $ hg ci -qm 3
+  $ hg topic --clear
+  $ echo 4 > foo
+  $ hg ci -qm 4
+
+  $ tlog 'all()'
+  0: 
+  1: featureA
+  2: featureA
+  3: featureA
+  4: 
+
+  $ hg stack
+  ### target: default (branch)
+  s2@ 4 (current)
+    ^ 3
+  s1: 0
+
+  $ tlog 'tip#stack[0]'
+  $ tlog 'tip#stack[1]'
+  0: 
+  $ tlog 'tip#stack[2]'
+  4: 
+
+  $ hg stack featureA
+  ### topic: featureA
+  ### target: default (branch), 3 behind
+  s3: 3
+  s2: 2
+  s1: 1
+  s0^ 0 (base)
+
+  $ tlog 'featureA#s[0]'
+  0: 
+  $ tlog 'featureA#s[1]'
+  1: featureA
+  $ tlog 'featureA#s[2]'
+  2: featureA
+  $ tlog 'featureA#s[3]'
+  3: featureA
+
+  $ tlog 'all()#s[-1]'
+  $ tlog 'all()#s[0]'
+  0: 
+  $ tlog 'all()#s[1]'
+  0: 
+  1: featureA
+  $ tlog 'all()#s[9999]'
+
+  $ hg topic featureB
+  marked working directory as topic: featureB
+  $ hg stack
+  ### topic: featureB
+  ### target: default (branch)
+  (stack is empty)
+  s0^ 4 (base current)
+  $ tlog 'wdir()#s[0]'
+  4: 
+
+  $ cd ..
+
 Testing the new config knob to forbid untopiced commit
 ======================================================