--- a/tests/test-topic-stack.t	Mon Sep 04 12:41:30 2017 +0200
+++ b/tests/test-topic-stack.t	Sat Sep 09 22:32:44 2017 +0530
@@ -550,3 +550,227 @@
     ^ c_D
   t1: c_f
   t0^ c_e (base)
+
+case involving a merge
+----------------------
+
+  $ cd ..
+  $ hg init stack-gap-merge
+  $ cd stack-gap-merge
+
+  $ echo aaa > aaa
+  $ hg commit -Am 'c_A'
+  adding aaa
+  $ hg topic red
+  $ echo bbb > bbb
+  $ hg commit -Am 'c_B'
+  adding bbb
+  $ echo ccc > ccc
+  $ hg commit -Am 'c_C'
+  adding ccc
+  $ hg topic blue
+  $ echo ddd > ddd
+  $ hg commit -Am 'c_D'
+  adding ddd
+  $ hg up 'desc("c_B")'
+  switching to topic red
+  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
+  $ echo eee > eee
+  $ hg commit -Am 'c_E'
+  adding eee
+  $ echo fff > fff
+  $ hg commit -Am 'c_F'
+  adding fff
+  $ hg topic blue
+  $ echo ggg > ggg
+  $ hg commit -Am 'c_G'
+  adding ggg
+  $ hg up 'desc("c_D")'
+  2 files updated, 0 files merged, 3 files removed, 0 files unresolved
+  $ hg topic red
+  $ hg merge 'desc("c_G")'
+  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ hg commit -Am 'c_H'
+  $ hg topic blue
+  $ echo iii > iii
+  $ hg ci -Am 'c_I'
+  adding iii
+
+  $ hg log -G
+  @  8 default {blue} draft c_I
+  |
+  o    7 default {red} draft c_H
+  |\
+  | o  6 default {blue} draft c_G
+  | |
+  | o  5 default {red} draft c_F
+  | |
+  | o  4 default {red} draft c_E
+  | |
+  o |  3 default {blue} draft c_D
+  | |
+  o |  2 default {red} draft c_C
+  |/
+  o  1 default {red} draft c_B
+  |
+  o  0 default {} draft c_A
+  
+
+  $ hg stack red
+  ### topic: red (3 heads)
+  ### branch: default, 6 behind
+  t5: c_C
+  t2^ c_B (base)
+  t4: c_F
+  t3: c_E
+  t2: c_B
+    ^ c_A
+  t1: c_H
+  t0^ c_D (base)
+  $ hg stack blue
+  ### topic: blue (3 heads)
+  ### branch: default, ambigious rebase destination
+  t3: c_D
+    ^ c_C
+  t2: c_G
+    ^ c_F
+  t1@ c_I (current)
+  t0^ c_H (base)
+
+Even with some obsolete and orphan changesets
+
+(the ordering of each branch of "blue" change because their hash change. we
+should stabilize this eventuelly)
+
+  $ hg up 'desc("c_B")'
+  switching to topic red
+  0 files updated, 0 files merged, 6 files removed, 0 files unresolved
+  $ hg commit --amend --user test2
+  $ hg up 'desc("c_C")'
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg commit --amend --user test2
+  $ hg up 'desc("c_D")'
+  switching to topic blue
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg commit --amend --user test2
+
+  $ hg log -G --rev 'sort(all(), "topo")'
+  @  11 default {blue} draft c_D
+  |
+  | o  8 default {blue} draft c_I
+  | |
+  | o    7 default {red} draft c_H
+  | |\
+  | | o  6 default {blue} draft c_G
+  | | |
+  | | o  5 default {red} draft c_F
+  | | |
+  | | o  4 default {red} draft c_E
+  | | |
+  | x |  3 default {blue} draft c_D
+  |/ /
+  x /  2 default {red} draft c_C
+  |/
+  | o  10 default {red} draft c_C
+  |/
+  x  1 default {red} draft c_B
+  |
+  | o  9 default {red} draft c_B
+  |/
+  o  0 default {} draft c_A
+  
+
+  $ hg stack red
+  ### topic: red (3 heads)
+  ### branch: default, ambigious rebase destination
+  t5$ c_H (unstable)
+    ^ c_D
+  t4$ c_C (unstable)
+  t1^ c_B (base)
+  t3$ c_F (unstable)
+  t2$ c_E (unstable)
+  t1: c_B
+  t0^ c_A (base)
+  $ hg stack blue
+  ### topic: blue (3 heads)
+  ### branch: default, ambigious rebase destination
+  t3$ c_G (unstable)
+    ^ c_F
+  t2$ c_I (unstable)
+    ^ c_H
+  t1$ c_D (current unstable)
+  t0^ c_C (base)
+
+more obsolescence
+
+  $ hg up 'max(desc("c_H"))'
+  switching to topic red
+  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg commit --amend --user test3
+  $ hg up 'max(desc("c_G"))'
+  switching to topic blue
+  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
+  $ hg commit --amend --user test3
+  $ hg up 'max(desc("c_B"))'
+  switching to topic red
+  0 files updated, 0 files merged, 3 files removed, 0 files unresolved
+  $ hg commit --amend --user test3
+  $ hg up 'max(desc("c_C"))'
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg commit --amend --user test3
+  $ hg up 'max(desc("c_D"))'
+  switching to topic blue
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg commit --amend --user test3
+
+  $ hg log -G --rev 'sort(all(), "topo")'
+  @  16 default {blue} draft c_D
+  |
+  | o  13 default {blue} draft c_G
+  | |
+  | | o    12 default {red} draft c_H
+  | | |\
+  | | | | o  8 default {blue} draft c_I
+  | | | | |
+  | | +---x  7 default {red} draft c_H
+  | | | |/
+  | +---x  6 default {blue} draft c_G
+  | | |
+  | o |  5 default {red} draft c_F
+  | | |
+  | o |  4 default {red} draft c_E
+  | | |
+  +---x  3 default {blue} draft c_D
+  | |
+  x |  2 default {red} draft c_C
+  |/
+  | o  15 default {red} draft c_C
+  |/
+  x  1 default {red} draft c_B
+  |
+  | o  14 default {red} draft c_B
+  |/
+  o  0 default {} draft c_A
+  
+
+  $ hg stack red
+  ### topic: red (3 heads)
+  ### branch: default, ambigious rebase destination
+  t5$ c_H (unstable)
+    ^ c_D
+  t4$ c_F (unstable)
+  t3$ c_E (unstable)
+  t1^ c_B (base)
+  t2$ c_C (unstable)
+  t1: c_B
+  t0^ c_A (base)
+  $ hg stack blue
+  ### topic: blue (3 heads)
+  ### branch: default, ambigious rebase destination
+  t3$ c_I (unstable)
+    ^ c_H
+  t2$ c_G (unstable)
+    ^ c_F
+  t1$ c_D (current unstable)
+  t0^ c_C (base)