diff -r 4e4fae1dda5c -r b6db2e80a9ce tests/test-issue5979.t
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/test-issue5979.t	Thu Sep 06 17:00:28 2018 -0400
@@ -0,0 +1,34 @@
+  $ hg init r1
+  $ cd r1
+  $ hg ci --config ui.allowemptycommit=true -m c0
+  $ hg ci --config ui.allowemptycommit=true -m c1
+  $ hg ci --config ui.allowemptycommit=true -m c2
+  $ hg co -q 0
+  $ hg ci --config ui.allowemptycommit=true -m c3
+  created new head
+  $ hg co -q 3
+  $ hg merge --quiet
+  $ hg ci --config ui.allowemptycommit=true -m c4
+
+  $ hg log -G -T'{desc}'
+  @    c4
+  |\
+  | o  c3
+  | |
+  o |  c2
+  | |
+  o |  c1
+  |/
+  o  c0
+  
+
+  >>> from mercurial.ui import ui
+  >>> from mercurial.hg import repository
+  >>> repo = repository(ui())
+  >>> for anc in repo.changelog.ancestors([4], inclusive=True):
+  ...   print(anc)
+  4
+  3
+  2
+  1
+  0