diff -r 66f01dd79f5d -r 1f92a6aa40d6 tests/test-amend.t
--- a/tests/test-amend.t	Wed Jan 01 21:36:21 2020 +0530
+++ b/tests/test-amend.t	Mon Nov 04 01:30:50 2019 +0530
@@ -121,6 +121,9 @@
   update: (current)
   phases: 3 draft
 
+setting the user after we have performed the test with no username
+  $ HGUSER=test
+
 Check the help
   $ hg amend -h
   hg amend [OPTION]... [FILE]...
@@ -170,3 +173,63 @@
   $ hg amend --patch --extract
   abort: cannot use both --patch and --extract
   [255]
+
+  $ cd ..
+
+Check the pre-check logic for content-divergence
+  $ hg init precheckrepo
+  $ cd precheckrepo
+  $ echo a > a
+  $ hg ci -Am "added a"
+  adding a
+  $ echo newchanges > a
+  $ hg amend
+  $ hg up 0 --hidden -q
+  updated to hidden changeset 9092f1db7931
+  (hidden revision '9092f1db7931' was rewritten as: aafaf407b00d)
+  working directory parent is obsolete! (9092f1db7931)
+
+when rewritting an already rewritten changeset (i.e cset being rewritten will
+be the base of divergence)
+  $ hg amend -m "i am gonna create divergence"
+  abort: amend of 9092f1db7931 creates content-divergence with aafaf407b00d
+  (add --verbose for details or see 'hg help evolution.instability')
+  [255]
+  $ hg amend -m "i am gonna create divergence" --verbose
+  abort: amend of 9092f1db7931 creates content-divergence with aafaf407b00d
+      changeset 9092f1db7931 already have a successors as changeset aafaf407b00d
+      rewriting changeset 9092f1db7931 would create "content-divergence"
+      set experimental.evolution.allowdivergence=True to overwrite this check
+  (see 'hg help evolution.instability' for details on content-divergence)
+  [255]
+
+when rewritting a cset which has a predecessor with non-obsolete successor
+
+to prepare the repo
+1) create content-divergence
+2) remove divergence by pruning one of the divergent cset
+  $ echo edited_a > a
+  $ hg ci -m "edited a"
+  1 new orphan changesets
+  $ hg debugobsolete $(hg id -ir 0 --debug) $(hg id -ir 2 --debug)
+  1 new obsolescence markers
+  2 new content-divergent changesets
+
+remove divergence by pruning one side of divergenence
+  $ hg debugobsolete $(hg id -ir 2 --debug)
+  1 new obsolescence markers
+  obsoleted 1 changesets
+
+  $ hg evolve -l
+  $ hg amend -m "i am gonna create divergence"
+  abort: amend of f8c05838af90 creates content-divergence with aafaf407b00d, from 9092f1db7931
+  (add --verbose for details or see 'hg help evolution.instability')
+  [255]
+  $ hg amend -m "i am gonna create divergence" --verbose
+  abort: amend of f8c05838af90 creates content-divergence with aafaf407b00d, from 9092f1db7931
+      changeset f8c05838af90 is an evolution of changeset 9092f1db7931
+      changeset 9092f1db7931 already have a successors as changeset aafaf407b00d
+      rewriting changeset f8c05838af90 would create "content-divergence"
+      set experimental.evolution.allowdivergence=True to overwrite this check
+  (see 'hg help evolution.instability' for details on content-divergence)
+  [255]