revert: Don't implicitly stomp pending sequencer operation

Protect the user from forgetting about a pending sequencer operation
by immediately erroring out when an existing cherry-pick or revert
operation is in progress like:

  $ git cherry-pick foo
  ... conflict ...
  $ git cherry-pick moo
  error: .git/sequencer already exists
  hint: A cherry-pick or revert is in progress
  hint: Use --reset to forget about it
  fatal: cherry-pick failed

A naive version of this would break the following established ways of
working:

  $ git cherry-pick foo
  ... conflict ...
  $ git reset --hard  # I actually meant "moo" when I said "foo"
  $ git cherry-pick moo

  $ git cherry-pick foo
  ... conflict ...
  $ git commit # commit the resolution
  $ git cherry-pick moo # New operation

However, the previous patches "reset: Make reset remove the sequencer
state" and "revert: Remove sequencer state when no commits are
pending" make sure that this does not happen.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/t/t3510-cherry-pick-sequence.sh b/t/t3510-cherry-pick-sequence.sh
index a414086578..566a15ed8a 100755
--- a/t/t3510-cherry-pick-sequence.sh
+++ b/t/t3510-cherry-pick-sequence.sh
@@ -106,4 +106,13 @@ test_expect_success 'cherry-pick cleans up sequencer state when one commit is le
 	test_cmp expect actual
 '
 
+test_expect_success 'cherry-pick does not implicitly stomp an existing operation' '
+	pristine_detach initial &&
+	test_must_fail git cherry-pick base..anotherpick &&
+	test-chmtime -v +0 .git/sequencer >expect &&
+	test_must_fail git cherry-pick unrelatedpick &&
+	test-chmtime -v +0 .git/sequencer >actual &&
+	test_cmp expect actual
+'
+
 test_done