diff --git a/mercurial/debugcommands.py b/mercurial/debugcommands.py
--- a/mercurial/debugcommands.py
+++ b/mercurial/debugcommands.py
@@ -66,6 +66,7 @@
     simplemerge,
     smartset,
     sslutil,
+    stack,
     streamclone,
     templater,
     treediscovery,
@@ -2311,6 +2312,12 @@
     finally:
         s.close()
 
+@command('debugstack', [])
+def debugstack(ui, repo):
+    revs = stack.getstack(repo)
+    for c in revs:
+        ui.write("%s\n" % c)
+
 @command('debugsub',
     [('r', 'rev', '',
      _('revision to check'), _('REV'))],
diff --git a/tests/test-completion.t b/tests/test-completion.t
--- a/tests/test-completion.t
+++ b/tests/test-completion.t
@@ -113,6 +113,7 @@
   debugrevspec
   debugsetparents
   debugssl
+  debugstack
   debugsub
   debugsuccessorssets
   debugtemplate
@@ -293,6 +294,7 @@
   debugrevspec: optimize, show-revs, show-set, show-stage, no-optimized, verify-optimized
   debugsetparents: 
   debugssl: 
+  debugstack: 
   debugsub: rev
   debugsuccessorssets: closest
   debugtemplate: rev, define
diff --git a/tests/test-help.t b/tests/test-help.t
--- a/tests/test-help.t
+++ b/tests/test-help.t
@@ -970,6 +970,7 @@
    debugsetparents
                  manually set the parents of the current working directory
    debugssl      test a secure connection to a server
+   debugstack    (no help text available)
    debugsub      (no help text available)
    debugsuccessorssets
                  show set of successors for revision
diff --git a/tests/test-stack.t b/tests/test-stack.t
new file mode 100644
--- /dev/null
+++ b/tests/test-stack.t
@@ -0,0 +1,213 @@
+
+This test test the low-level definition of stack, agnostic from all formatting
+
+Initial setup
+
+  $ cat << EOF >> $HGRCPATH
+  > [ui]
+  > logtemplate = {rev} {branch} {phase} {desc|firstline}\n
+  > [extensions]
+  > rebase=
+  > [experimental]
+  > evolution=createmarkers,exchange,allowunstable
+  > EOF
+
+  $ hg init main
+  $ cd main
+  $ hg branch other
+  marked working directory as branch other
+  (branches are permanent and global, did you want a bookmark?)
+  $ echo aaa > aaa
+  $ hg add aaa
+  $ hg commit -m c_a
+  $ echo aaa > bbb
+  $ hg add bbb
+  $ hg commit -m c_b
+  $ hg branch foo
+  marked working directory as branch foo
+  $ echo aaa > ccc
+  $ hg add ccc
+  $ hg commit -m c_c
+  $ echo aaa > ddd
+  $ hg add ddd
+  $ hg commit -m c_d
+  $ echo aaa > eee
+  $ hg add eee
+  $ hg commit -m c_e
+  $ echo aaa > fff
+  $ hg add fff
+  $ hg commit -m c_f
+  $ hg log -G
+  @  5 foo draft c_f
+  |
+  o  4 foo draft c_e
+  |
+  o  3 foo draft c_d
+  |
+  o  2 foo draft c_c
+  |
+  o  1 other draft c_b
+  |
+  o  0 other draft c_a
+  
+
+Check that stack doesn't include public changesets
+--------------------------------------------------
+
+  $ hg up other
+  0 files updated, 0 files merged, 4 files removed, 0 files unresolved
+  $ hg debugstack
+  1
+  0
+  $ hg phase --public 'branch("other")'
+  $ hg debugstack
+  $ hg up foo
+  4 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
+Simple test
+-----------
+
+'hg debugstack' list all changeset in the branch
+
+  $ hg branch
+  foo
+  $ hg debugstack
+  5
+  4
+  3
+  2
+
+Case with some of the branch unstable
+------------------------------------
+
+  $ hg up 3
+  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
+  $ echo bbb > ddd
+  $ hg commit --amend
+  2 new orphan changesets
+  $ hg log -G
+  @  6 foo draft c_d
+  |
+  | *  5 foo draft c_f
+  | |
+  | *  4 foo draft c_e
+  | |
+  | x  3 foo draft c_d
+  |/
+  o  2 foo draft c_c
+  |
+  o  1 other public c_b
+  |
+  o  0 other public c_a
+  
+  $ hg debugstack
+  6
+  $ hg up -r "desc(c_e)"
+  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg debugstack
+  4
+  3
+  $ hg up -r "desc(c_d)"
+  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+
+  $ hg debugstack
+  6
+
+Case with multiple topological heads
+------------------------------------
+
+Make things linear again
+
+  $ hg rebase -s 'desc(c_e)' -d 'desc(c_d) - obsolete()'
+  rebasing 4:4f2a69f6d380 "c_e"
+  rebasing 5:913c298d8b0a "c_f"
+  $ hg log -G
+  o  8 foo draft c_f
+  |
+  o  7 foo draft c_e
+  |
+  @  6 foo draft c_d
+  |
+  o  2 foo draft c_c
+  |
+  o  1 other public c_b
+  |
+  o  0 other public c_a
+  
+
+Create the second branch
+
+  $ hg up 'desc(c_d)'
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ echo aaa > ggg
+  $ hg add ggg
+  $ hg commit -m c_g
+  created new head
+  $ echo aaa > hhh
+  $ hg add hhh
+  $ hg commit -m c_h
+  $ hg log -G
+  @  10 foo draft c_h
+  |
+  o  9 foo draft c_g
+  |
+  | o  8 foo draft c_f
+  | |
+  | o  7 foo draft c_e
+  |/
+  o  6 foo draft c_d
+  |
+  o  2 foo draft c_c
+  |
+  o  1 other public c_b
+  |
+  o  0 other public c_a
+  
+
+Test output
+
+  $ hg debugstack
+  10
+  9
+  $ hg up 'desc(c_f)'
+  2 files updated, 0 files merged, 2 files removed, 0 files unresolved
+  $ hg debugstack
+  8
+  7
+
+Case with multiple heads with unstability involved
+--------------------------------------------------
+
+We amend the message to make sure the display base pick the right changeset
+
+  $ hg up 'desc(c_d)'
+  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
+  $ echo ccc > ddd
+  $ hg commit --amend -m 'c_D'
+  4 new orphan changesets
+  $ hg rebase -d . -s 'desc(c_g)'
+  rebasing 9:2ebb6e48ab8a "c_g"
+  rebasing 10:634f38e27a1d "c_h"
+  $ hg log -G
+  o  13 foo draft c_h
+  |
+  o  12 foo draft c_g
+  |
+  @  11 foo draft c_D
+  |
+  | *  8 foo draft c_f
+  | |
+  | *  7 foo draft c_e
+  | |
+  | x  6 foo draft c_d
+  |/
+  o  2 foo draft c_c
+  |
+  o  1 other public c_b
+  |
+  o  0 other public c_a
+  
+
+We should improve stack definition to also show 12 and 13 here
+  $ hg debugstack
+  11