commit: give correct advice for empty commit during a rebase

In dcb500dc16c (cherry-pick/revert: advise using --skip, 2019-07-02),
`git commit` learned to suggest to run `git cherry-pick --skip` when
trying to cherry-pick an empty patch.

However, it was overlooked that there are more conditions than just a
`git cherry-pick` when this advice is printed (which originally
suggested the neutral `git reset`): the same can happen during a rebase.

Let's suggest the correct command, even during a rebase.

While at it, we adjust more places in `builtin/commit.c` that
incorrectly assumed that the presence of a `CHERRY_PICK_HEAD` meant that
surely this must be a `cherry-pick` in progress.

Note: we take pains to handle the situation when a user runs a `git
cherry-pick` _during_ a rebase. This is quite valid (e.g. in an `exec`
line in an interactive rebase). On the other hand, it is not possible to
run a rebase during a cherry-pick, meaning: if both `rebase-merge/` and
`sequencer/` exist or CHERRY_PICK_HEAD and REBASE_HEAD point to the same
commit , we still want to advise to use `git cherry-pick --skip`.

Original-patch-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 57 insertions, 5 deletions

diff --git a/t/t3403-rebase-skip.sh b/t/t3403-rebase-skip.sh
index db7e917248..a927774910 100755
--- a/t/t3403-rebase-skip.sh
+++ b/t/t3403-rebase-skip.sh
@@ -97,9 +97,9 @@ test_expect_success 'correct advice upon picking empty commit' '
 	test_must_fail git rebase -i --onto goodbye \
 		amended-goodbye^ amended-goodbye 2>err &&
 	test_i18ngrep "previous cherry-pick is now empty" err &&
-	test_i18ngrep "git cherry-pick --skip" err &&
+	test_i18ngrep "git rebase --skip" err &&
 	test_must_fail git commit &&
-	test_i18ngrep "git cherry-pick --skip" err
+	test_i18ngrep "git rebase --skip" err
 '
 
 test_expect_success 'correct authorship when committing empty pick' '
@@ -120,9 +120,9 @@ test_expect_success 'correct advice upon rewording empty commit' '
 			--onto goodbye amended-goodbye^ amended-goodbye 2>err
 	) &&
 	test_i18ngrep "previous cherry-pick is now empty" err &&
-	test_i18ngrep "git cherry-pick --skip" err &&
+	test_i18ngrep "git rebase --skip" err &&
 	test_must_fail git commit &&
-	test_i18ngrep "git cherry-pick --skip" err
+	test_i18ngrep "git rebase --skip" err
 '
 
 test_expect_success 'correct advice upon editing empty commit' '
@@ -133,8 +133,34 @@ test_expect_success 'correct advice upon editing empty commit' '
 			--onto goodbye amended-goodbye^ amended-goodbye 2>err
 	) &&
 	test_i18ngrep "previous cherry-pick is now empty" err &&
-	test_i18ngrep "git cherry-pick --skip" err &&
+	test_i18ngrep "git rebase --skip" err &&
 	test_must_fail git commit &&
+	test_i18ngrep "git rebase --skip" err
+'
+
+test_expect_success 'correct advice upon cherry-picking an empty commit during a rebase' '
+	test_when_finished "git rebase --abort" &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="1 exec_git_cherry-pick_amended-goodbye" \
+			git rebase -i goodbye^ goodbye 2>err
+	) &&
+	test_i18ngrep "previous cherry-pick is now empty" err &&
+	test_i18ngrep "git cherry-pick --skip" err &&
+	test_must_fail git commit 2>err &&
+	test_i18ngrep "git cherry-pick --skip" err
+'
+
+test_expect_success 'correct advice upon multi cherry-pick picking an empty commit during a rebase' '
+	test_when_finished "git rebase --abort" &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="1 exec_git_cherry-pick_goodbye_amended-goodbye" \
+			git rebase -i goodbye^^ goodbye 2>err
+	) &&
+	test_i18ngrep "previous cherry-pick is now empty" err &&
+	test_i18ngrep "git cherry-pick --skip" err &&
+	test_must_fail git commit 2>err &&
 	test_i18ngrep "git cherry-pick --skip" err
 '
 
diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
index 99ecd2579f..cdbf763385 100755
--- a/t/t3404-rebase-interactive.sh
+++ b/t/t3404-rebase-interactive.sh
@@ -1599,6 +1599,32 @@ test_expect_success 'post-commit hook is called' '
 	test_cmp expect actual
 '
 
+test_expect_success 'correct error message for partial commit after empty pick' '
+	test_when_finished "git rebase --abort" &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="2 1 1" &&
+		export FAKE_LINES &&
+		test_must_fail git rebase -i A D
+	) &&
+	echo x >file1 &&
+	test_must_fail git commit file1 2>err &&
+	test_i18ngrep "cannot do a partial commit during a rebase." err
+'
+
+test_expect_success 'correct error message for commit --amend after empty pick' '
+	test_when_finished "git rebase --abort" &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 1" &&
+		export FAKE_LINES &&
+		test_must_fail git rebase -i A D
+	) &&
+	echo x>file1 &&
+	test_must_fail git commit -a --amend 2>err &&
+	test_i18ngrep "middle of a rebase -- cannot amend." err
+'
+
 # This must be the last test in this file
 test_expect_success '$EDITOR and friends are unchanged' '
 	test_editor_unchanged