From 0af38890ade347536af7690ecee9e5e75d1b2b12 Mon Sep 17 00:00:00 2001
From: Brian Lyles <brianmlyles@gmail.com>
Date: Mon, 25 Mar 2024 18:16:48 -0500
Subject: [PATCH 1/7] docs: address inaccurate `--empty` default with `--exec`

The documentation for git-rebase(1) indicates that using the `--exec`
option will use `--empty=drop`. This is inaccurate: when `--interactive`
is not explicitly provided, `--exec` results in `--empty=keep`
behaviors.

Correctly indicate the behavior of `--exec` using `--empty=keep` when
`--interactive` is not specified.

Reported-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Brian Lyles <brianmlyles@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/git-rebase.txt | 10 +++++-----
 t/t3424-rebase-empty.sh      | 38 ++++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 5 deletions(-)

diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index e7e725044d..a602e8fa81 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -295,11 +295,11 @@ See also INCOMPATIBLE OPTIONS below.
 	empty after rebasing (because they contain a subset of already
 	upstream changes).  With drop (the default), commits that
 	become empty are dropped.  With keep, such commits are kept.
-	With ask (implied by `--interactive`), the rebase will halt when
-	an empty commit is applied allowing you to choose whether to
-	drop it, edit files more, or just commit the empty changes.
-	Other options, like `--exec`, will use the default of drop unless
-	`-i`/`--interactive` is explicitly specified.
+	With ask, the rebase will halt when an empty commit is applied
+	allowing you to choose whether to drop it, edit files more, or just
+	commit the empty changes.
+	When the `-i`/`--interactive` option is used, the default becomes ask.
+	Otherwise, when the `--exec` option is used, the default becomes keep.
 +
 Note that commits which start empty are kept (unless `--no-keep-empty`
 is specified), and commits which are clean cherry-picks (as determined
diff --git a/t/t3424-rebase-empty.sh b/t/t3424-rebase-empty.sh
index 5e1045a0af..73ff35ced2 100755
--- a/t/t3424-rebase-empty.sh
+++ b/t/t3424-rebase-empty.sh
@@ -167,4 +167,42 @@ test_expect_success 'rebase --merge does not leave state laying around' '
 	test_path_is_missing .git/MERGE_MSG
 '
 
+test_expect_success 'rebase --exec --empty=drop' '
+	git checkout -B testing localmods &&
+	git rebase --exec "true" --empty=drop upstream &&
+
+	test_write_lines D C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --exec --empty=keep' '
+	git checkout -B testing localmods &&
+	git rebase --exec "true" --empty=keep upstream &&
+
+	test_write_lines D C2 C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --exec uses default of --empty=keep' '
+	git checkout -B testing localmods &&
+	git rebase --exec "true" upstream &&
+
+	test_write_lines D C2 C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --exec --empty=ask' '
+	git checkout -B testing localmods &&
+	test_must_fail git rebase --exec "true" --empty=ask upstream &&
+
+	git rebase --skip &&
+
+	test_write_lines D C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
 test_done

From 64a443efe4846d9cf09c7ff50cb9a6660fb49b50 Mon Sep 17 00:00:00 2001
From: Brian Lyles <brianmlyles@gmail.com>
Date: Mon, 25 Mar 2024 18:16:49 -0500
Subject: [PATCH 2/7] docs: clean up `--empty` formatting in git-rebase(1) and
 git-am(1)

Both of these pages document very similar `--empty` options, but with
different styles. The exact behavior of these `--empty` options differs
somewhat, but consistent styling in the docs is still beneficial. This
commit aims to make them more consistent.

Break the possible values for `--empty` into separate sections for
readability. Alphabetical order is chosen for consistency.

In a future commit, we'll be documenting a new `--empty` option for
git-cherry-pick(1), making the consistency even more relevant.

Signed-off-by: Brian Lyles <brianmlyles@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/git-am.txt     | 20 +++++++++++++-------
 Documentation/git-rebase.txt | 25 ++++++++++++++++---------
 2 files changed, 29 insertions(+), 16 deletions(-)

diff --git a/Documentation/git-am.txt b/Documentation/git-am.txt
index 463a3c6600..624a6e6fe4 100644
--- a/Documentation/git-am.txt
+++ b/Documentation/git-am.txt
@@ -66,13 +66,19 @@ OPTIONS
 --quoted-cr=<action>::
 	This flag will be passed down to 'git mailinfo' (see linkgit:git-mailinfo[1]).
 
---empty=(stop|drop|keep)::
-	By default, or when the option is set to 'stop', the command
-	errors out on an input e-mail message lacking a patch
-	and stops in the middle of the current am session. When this
-	option is set to 'drop', skip such an e-mail message instead.
-	When this option is set to 'keep', create an empty commit,
-	recording the contents of the e-mail message as its log.
+--empty=(drop|keep|stop)::
+	How to handle an e-mail message lacking a patch:
++
+--
+`drop`;;
+	The e-mail message will be skipped.
+`keep`;;
+	An empty commit will be created, with the contents of the e-mail
+	message as its log.
+`stop`;;
+	The command will fail, stopping in the middle of the current `am`
+	session. This is the default behavior.
+--
 
 -m::
 --message-id::
diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index a602e8fa81..17133bf382 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -289,17 +289,24 @@ See also INCOMPATIBLE OPTIONS below.
 +
 See also INCOMPATIBLE OPTIONS below.
 
---empty=(drop|keep|ask)::
+--empty=(ask|drop|keep)::
 	How to handle commits that are not empty to start and are not
 	clean cherry-picks of any upstream commit, but which become
 	empty after rebasing (because they contain a subset of already
-	upstream changes).  With drop (the default), commits that
-	become empty are dropped.  With keep, such commits are kept.
-	With ask, the rebase will halt when an empty commit is applied
-	allowing you to choose whether to drop it, edit files more, or just
-	commit the empty changes.
-	When the `-i`/`--interactive` option is used, the default becomes ask.
-	Otherwise, when the `--exec` option is used, the default becomes keep.
+	upstream changes):
++
+--
+`ask`;;
+	The rebase will halt when the commit is applied, allowing you to
+	choose whether to drop it, edit files more, or just commit the empty
+	changes. This option is implied when `-i`/`--interactive` is
+	specified.
+`drop`;;
+	The commit will be dropped. This is the default behavior.
+`keep`;;
+	The commit will be kept. This option is implied when `--exec` is
+	specified unless `-i`/`--interactive` is also specified.
+--
 +
 Note that commits which start empty are kept (unless `--no-keep-empty`
 is specified), and commits which are clean cherry-picks (as determined
@@ -704,7 +711,7 @@ be dropped automatically with `--no-keep-empty`).
 Similar to the apply backend, by default the merge backend drops
 commits that become empty unless `-i`/`--interactive` is specified (in
 which case it stops and asks the user what to do).  The merge backend
-also has an `--empty=(drop|keep|ask)` option for changing the behavior
+also has an `--empty=(ask|drop|keep)` option for changing the behavior
 of handling commits that become empty.
 
 Directory rename detection

From c282eba2d561b726e4a60c8837e4eaa2ac6537fa Mon Sep 17 00:00:00 2001
From: Brian Lyles <brianmlyles@gmail.com>
Date: Mon, 25 Mar 2024 18:16:50 -0500
Subject: [PATCH 3/7] rebase: update `--empty=ask` to `--empty=stop`

When git-am(1) got its own `--empty` option in 7c096b8d61 (am: support
--empty=<option> to handle empty patches, 2021-12-09), `stop` was used
instead of `ask`. `stop` is a more accurate term for describing what
really happens, and consistency is good.

Update git-rebase(1) to also use `stop`, while keeping `ask` as a
deprecated synonym. Update the tests to primarily use `stop`, but also
ensure that `ask` is still allowed.

In a future commit, we'll be adding a new `--empty` option for
git-cherry-pick(1) as well, making the consistency even more relevant.

Reported-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Brian Lyles <brianmlyles@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/git-rebase.txt | 15 ++++++++-------
 builtin/rebase.c             | 16 ++++++++++------
 t/t3424-rebase-empty.sh      | 21 ++++++++++++++++-----
 3 files changed, 34 insertions(+), 18 deletions(-)

diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index 17133bf382..00a9453a39 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -289,23 +289,24 @@ See also INCOMPATIBLE OPTIONS below.
 +
 See also INCOMPATIBLE OPTIONS below.
 
---empty=(ask|drop|keep)::
+--empty=(drop|keep|stop)::
 	How to handle commits that are not empty to start and are not
 	clean cherry-picks of any upstream commit, but which become
 	empty after rebasing (because they contain a subset of already
 	upstream changes):
 +
 --
-`ask`;;
-	The rebase will halt when the commit is applied, allowing you to
-	choose whether to drop it, edit files more, or just commit the empty
-	changes. This option is implied when `-i`/`--interactive` is
-	specified.
 `drop`;;
 	The commit will be dropped. This is the default behavior.
 `keep`;;
 	The commit will be kept. This option is implied when `--exec` is
 	specified unless `-i`/`--interactive` is also specified.
+`stop`;;
+`ask`;;
+	The rebase will halt when the commit is applied, allowing you to
+	choose whether to drop it, edit files more, or just commit the empty
+	changes. This option is implied when `-i`/`--interactive` is
+	specified. `ask` is a deprecated synonym of `stop`.
 --
 +
 Note that commits which start empty are kept (unless `--no-keep-empty`
@@ -711,7 +712,7 @@ be dropped automatically with `--no-keep-empty`).
 Similar to the apply backend, by default the merge backend drops
 commits that become empty unless `-i`/`--interactive` is specified (in
 which case it stops and asks the user what to do).  The merge backend
-also has an `--empty=(ask|drop|keep)` option for changing the behavior
+also has an `--empty=(drop|keep|stop)` option for changing the behavior
 of handling commits that become empty.
 
 Directory rename detection
diff --git a/builtin/rebase.c b/builtin/rebase.c
index 6ead9465a4..ab3e187473 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -58,7 +58,7 @@ enum empty_type {
 	EMPTY_UNSPECIFIED = -1,
 	EMPTY_DROP,
 	EMPTY_KEEP,
-	EMPTY_ASK
+	EMPTY_STOP
 };
 
 enum action {
@@ -951,10 +951,14 @@ static enum empty_type parse_empty_value(const char *value)
 		return EMPTY_DROP;
 	else if (!strcasecmp(value, "keep"))
 		return EMPTY_KEEP;
-	else if (!strcasecmp(value, "ask"))
-		return EMPTY_ASK;
+	else if (!strcasecmp(value, "stop"))
+		return EMPTY_STOP;
+	else if (!strcasecmp(value, "ask")) {
+		warning(_("--empty=ask is deprecated; use '--empty=stop' instead."));
+		return EMPTY_STOP;
+	}
 
-	die(_("unrecognized empty type '%s'; valid values are \"drop\", \"keep\", and \"ask\"."), value);
+	die(_("unrecognized empty type '%s'; valid values are \"drop\", \"keep\", and \"stop\"."), value);
 }
 
 static int parse_opt_keep_empty(const struct option *opt, const char *arg,
@@ -1133,7 +1137,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 				 "instead of ignoring them"),
 			      1, PARSE_OPT_HIDDEN),
 		OPT_RERERE_AUTOUPDATE(&options.allow_rerere_autoupdate),
-		OPT_CALLBACK_F(0, "empty", &options, "(drop|keep|ask)",
+		OPT_CALLBACK_F(0, "empty", &options, "(drop|keep|stop)",
 			       N_("how to handle commits that become empty"),
 			       PARSE_OPT_NONEG, parse_opt_empty),
 		OPT_CALLBACK_F('k', "keep-empty", &options, NULL,
@@ -1550,7 +1554,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 
 	if (options.empty == EMPTY_UNSPECIFIED) {
 		if (options.flags & REBASE_INTERACTIVE_EXPLICIT)
-			options.empty = EMPTY_ASK;
+			options.empty = EMPTY_STOP;
 		else if (options.exec.nr > 0)
 			options.empty = EMPTY_KEEP;
 		else
diff --git a/t/t3424-rebase-empty.sh b/t/t3424-rebase-empty.sh
index 73ff35ced2..1ee6b00fd5 100755
--- a/t/t3424-rebase-empty.sh
+++ b/t/t3424-rebase-empty.sh
@@ -72,6 +72,17 @@ test_expect_success 'rebase --merge --empty=keep' '
 	test_cmp expect actual
 '
 
+test_expect_success 'rebase --merge --empty=stop' '
+	git checkout -B testing localmods &&
+	test_must_fail git rebase --merge --empty=stop upstream &&
+
+	git rebase --skip &&
+
+	test_write_lines D C B A >expect &&
+	git log --format=%s >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'rebase --merge --empty=ask' '
 	git checkout -B testing localmods &&
 	test_must_fail git rebase --merge --empty=ask upstream &&
@@ -101,9 +112,9 @@ test_expect_success 'rebase --interactive --empty=keep' '
 	test_cmp expect actual
 '
 
-test_expect_success 'rebase --interactive --empty=ask' '
+test_expect_success 'rebase --interactive --empty=stop' '
 	git checkout -B testing localmods &&
-	test_must_fail git rebase --interactive --empty=ask upstream &&
+	test_must_fail git rebase --interactive --empty=stop upstream &&
 
 	git rebase --skip &&
 
@@ -112,7 +123,7 @@ test_expect_success 'rebase --interactive --empty=ask' '
 	test_cmp expect actual
 '
 
-test_expect_success 'rebase --interactive uses default of --empty=ask' '
+test_expect_success 'rebase --interactive uses default of --empty=stop' '
 	git checkout -B testing localmods &&
 	test_must_fail git rebase --interactive upstream &&
 
@@ -194,9 +205,9 @@ test_expect_success 'rebase --exec uses default of --empty=keep' '
 	test_cmp expect actual
 '
 
-test_expect_success 'rebase --exec --empty=ask' '
+test_expect_success 'rebase --exec --empty=stop' '
 	git checkout -B testing localmods &&
-	test_must_fail git rebase --exec "true" --empty=ask upstream &&
+	test_must_fail git rebase --exec "true" --empty=stop upstream &&
 
 	git rebase --skip &&
 

From 1b90588d620a2970c82025c272e14f32d5e5969d Mon Sep 17 00:00:00 2001
From: Brian Lyles <brianmlyles@gmail.com>
Date: Mon, 25 Mar 2024 18:16:51 -0500
Subject: [PATCH 4/7] sequencer: handle unborn branch with `--allow-empty`

When using git-cherry-pick(1) with `--allow-empty` while on an unborn
branch, an error is thrown. This is inconsistent with the same
cherry-pick when `--allow-empty` is not specified.

Detect unborn branches in `is_index_unchanged`. When on an unborn
branch, use the `empty_tree` as the tree to compare against.

Add a new test to cover this scenario. While modelled off of the
existing 'cherry-pick on unborn branch' test, some improvements can be
made:

- Use `git switch --orphan unborn` instead of `git checkout --orphan
  unborn` to avoid the need for a separate `rm -rf *` call
- Avoid using `--quiet` in the `git diff` call to make debugging easier
  in the event of a failure. Use simply `--exit-code` instead.

Make these improvements to the existing test as well as the new test.

Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Brian Lyles <brianmlyles@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 sequencer.c                   | 41 +++++++++++++++++++++++------------
 t/t3501-revert-cherry-pick.sh | 14 +++++++++---
 2 files changed, 38 insertions(+), 17 deletions(-)

diff --git a/sequencer.c b/sequencer.c
index 35dd7e561a..ff0b3f4f06 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -772,29 +772,42 @@ static struct object_id *get_cache_tree_oid(struct index_state *istate)
 static int is_index_unchanged(struct repository *r)
 {
 	struct object_id head_oid, *cache_tree_oid;
+	const struct object_id *head_tree_oid;
 	struct commit *head_commit;
 	struct index_state *istate = r->index;
+	const char *head_name;
 
-	if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &head_oid, NULL))
-		return error(_("could not resolve HEAD commit"));
+	if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &head_oid, NULL)) {
+		/* Check to see if this is an unborn branch */
+		head_name = resolve_ref_unsafe("HEAD",
+			RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
+			&head_oid, NULL);
+		if (!head_name ||
+			!starts_with(head_name, "refs/heads/") ||
+			!is_null_oid(&head_oid))
+			return error(_("could not resolve HEAD commit"));
+		head_tree_oid = the_hash_algo->empty_tree;
+	} else {
+		head_commit = lookup_commit(r, &head_oid);
 
-	head_commit = lookup_commit(r, &head_oid);
+		/*
+		 * If head_commit is NULL, check_commit, called from
+		 * lookup_commit, would have indicated that head_commit is not
+		 * a commit object already.  repo_parse_commit() will return failure
+		 * without further complaints in such a case.  Otherwise, if
+		 * the commit is invalid, repo_parse_commit() will complain.  So
+		 * there is nothing for us to say here.  Just return failure.
+		 */
+		if (repo_parse_commit(r, head_commit))
+			return -1;
 
-	/*
-	 * If head_commit is NULL, check_commit, called from
-	 * lookup_commit, would have indicated that head_commit is not
-	 * a commit object already.  repo_parse_commit() will return failure
-	 * without further complaints in such a case.  Otherwise, if
-	 * the commit is invalid, repo_parse_commit() will complain.  So
-	 * there is nothing for us to say here.  Just return failure.
-	 */
-	if (repo_parse_commit(r, head_commit))
-		return -1;
+		head_tree_oid = get_commit_tree_oid(head_commit);
+	}
 
 	if (!(cache_tree_oid = get_cache_tree_oid(istate)))
 		return -1;
 
-	return oideq(cache_tree_oid, get_commit_tree_oid(head_commit));
+	return oideq(cache_tree_oid, head_tree_oid);
 }
 
 static int write_author_script(const char *message)
diff --git a/t/t3501-revert-cherry-pick.sh b/t/t3501-revert-cherry-pick.sh
index aeab689a98..af73227512 100755
--- a/t/t3501-revert-cherry-pick.sh
+++ b/t/t3501-revert-cherry-pick.sh
@@ -104,11 +104,19 @@ test_expect_success 'revert forbidden on dirty working tree' '
 '
 
 test_expect_success 'cherry-pick on unborn branch' '
-	git checkout --orphan unborn &&
+	git switch --orphan unborn &&
 	git rm --cached -r . &&
-	rm -rf * &&
 	git cherry-pick initial &&
-	git diff --quiet initial &&
+	git diff --exit-code initial &&
+	test_cmp_rev ! initial HEAD
+'
+
+test_expect_success 'cherry-pick on unborn branch with --allow-empty' '
+	git checkout --detach &&
+	git branch -D unborn &&
+	git switch --orphan unborn &&
+	git cherry-pick initial --allow-empty &&
+	git diff --exit-code initial &&
 	test_cmp_rev ! initial HEAD
 '
 

From 661b671aec3683718fe58f78f85359a11f57a57a Mon Sep 17 00:00:00 2001
From: Brian Lyles <brianmlyles@gmail.com>
Date: Mon, 25 Mar 2024 18:16:52 -0500
Subject: [PATCH 5/7] sequencer: do not require `allow_empty` for redundant
 commit options

A consumer of the sequencer that wishes to take advantage of either the
`keep_redundant_commits` or `drop_redundant_commits` feature must also
specify `allow_empty`. However, these refer to two distinct types of
empty commits:

- `allow_empty` refers specifically to commits which start empty
- `keep_redundant_commits` refers specifically to commits that do not
  start empty, but become empty due to the content already existing in
  the target history

Conceptually, there is no reason that the behavior for handling one of
these should be entangled with the other. It is particularly unintuitive
to require `allow_empty` in order for `drop_redundant_commits` to have
an effect: in order to prevent redundant commits automatically,
initially-empty commits would need to be kept automatically as well.

Instead, rewrite the `allow_empty()` logic to remove the over-arching
requirement that `allow_empty` be specified in order to reach any of the
keep/drop behaviors. Only if the commit was originally empty will
`allow_empty` have an effect.

Note that no behavioral changes should result from this commit -- it
merely sets the stage for future commits. In one such future commit, an
`--empty` option will be added to git-cherry-pick(1), meaning that
`drop_redundant_commits` will be used by that command.

Signed-off-by: Brian Lyles <brianmlyles@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 sequencer.c | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/sequencer.c b/sequencer.c
index ff0b3f4f06..1964977545 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -1734,34 +1734,25 @@ static int allow_empty(struct repository *r,
 	int index_unchanged, originally_empty;
 
 	/*
-	 * Four cases:
+	 * For a commit that is initially empty, allow_empty determines if it
+	 * should be kept or not
 	 *
-	 * (1) we do not allow empty at all and error out.
-	 *
-	 * (2) we allow ones that were initially empty, and
-	 *     just drop the ones that become empty
-	 *
-	 * (3) we allow ones that were initially empty, but
-	 *     halt for the ones that become empty;
-	 *
-	 * (4) we allow both.
+	 * For a commit that becomes empty, keep_redundant_commits and
+	 * drop_redundant_commits determine whether the commit should be kept or
+	 * dropped. If neither is specified, halt.
 	 */
-	if (!opts->allow_empty)
-		return 0; /* let "git commit" barf as necessary */
-
 	index_unchanged = is_index_unchanged(r);
 	if (index_unchanged < 0)
 		return index_unchanged;
 	if (!index_unchanged)
 		return 0; /* we do not have to say --allow-empty */
 
-	if (opts->keep_redundant_commits)
-		return 1;
-
 	originally_empty = is_original_commit_empty(commit);
 	if (originally_empty < 0)
 		return originally_empty;
 	if (originally_empty)
+		return opts->allow_empty;
+	else if (opts->keep_redundant_commits)
 		return 1;
 	else if (opts->drop_redundant_commits)
 		return 2;

From bd2f9fd025e3aa2926f249e9c24f1f648e89d997 Mon Sep 17 00:00:00 2001
From: Brian Lyles <brianmlyles@gmail.com>
Date: Mon, 25 Mar 2024 18:16:53 -0500
Subject: [PATCH 6/7] cherry-pick: enforce `--keep-redundant-commits`
 incompatibility

When `--keep-redundant-commits` was added in  b27cfb0d8d
(git-cherry-pick: Add keep-redundant-commits option, 2012-04-20), it was
not marked as incompatible with the various operations needed to
continue or exit a cherry-pick (`--continue`, `--skip`, `--abort`, and
`--quit`).

Enforce this incompatibility via `verify_opt_compatible` like we do for
the other various options.

Signed-off-by: Brian Lyles <brianmlyles@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/revert.c             |  1 +
 t/t3505-cherry-pick-empty.sh | 14 ++++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/builtin/revert.c b/builtin/revert.c
index 89821bab95..a1936ef70e 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -167,6 +167,7 @@ static int run_sequencer(int argc, const char **argv, const char *prefix,
 				"--ff", opts->allow_ff,
 				"--rerere-autoupdate", opts->allow_rerere_auto == RERERE_AUTOUPDATE,
 				"--no-rerere-autoupdate", opts->allow_rerere_auto == RERERE_NOAUTOUPDATE,
+				"--keep-redundant-commits", opts->keep_redundant_commits,
 				NULL);
 	}
 
diff --git a/t/t3505-cherry-pick-empty.sh b/t/t3505-cherry-pick-empty.sh
index eba3c38d5a..61f91aaa0a 100755
--- a/t/t3505-cherry-pick-empty.sh
+++ b/t/t3505-cherry-pick-empty.sh
@@ -99,4 +99,18 @@ test_expect_success 'cherry-pick a no-op with --keep-redundant' '
 	test_cmp expect actual
 '
 
+test_expect_success '--keep-redundant-commits is incompatible with operations' '
+	test_must_fail git cherry-pick HEAD 2>output &&
+	test_grep "The previous cherry-pick is now empty" output &&
+	test_must_fail git cherry-pick --keep-redundant-commits --continue 2>output &&
+	test_grep "fatal: cherry-pick: --keep-redundant-commits cannot be used with --continue" output &&
+	test_must_fail git cherry-pick --keep-redundant-commits --skip 2>output &&
+	test_grep "fatal: cherry-pick: --keep-redundant-commits cannot be used with --skip" output &&
+	test_must_fail git cherry-pick --keep-redundant-commits --abort 2>output &&
+	test_grep "fatal: cherry-pick: --keep-redundant-commits cannot be used with --abort" output &&
+	test_must_fail git cherry-pick --keep-redundant-commits --quit 2>output &&
+	test_grep "fatal: cherry-pick: --keep-redundant-commits cannot be used with --quit" output &&
+	git cherry-pick --abort
+'
+
 test_done

From ec79d763de617905bd9275de0b5941a160d6159b Mon Sep 17 00:00:00 2001
From: Brian Lyles <brianmlyles@gmail.com>
Date: Mon, 25 Mar 2024 18:16:54 -0500
Subject: [PATCH 7/7] cherry-pick: add `--empty` for more robust redundant
 commit handling

As with git-rebase(1) and git-am(1), git-cherry-pick(1) can result in a
commit being made redundant if the content from the picked commit is
already present in the target history. However, git-cherry-pick(1) does
not have the same options available that git-rebase(1) and git-am(1) have.

There are three things that can be done with these redundant commits:
drop them, keep them, or have the cherry-pick stop and wait for the user
to take an action. git-rebase(1) has the `--empty` option added in commit
e98c4269c8 (rebase (interactive-backend): fix handling of commits that
become empty, 2020-02-15), which handles all three of these scenarios.
Similarly, git-am(1) got its own `--empty` in 7c096b8d61 (am: support
--empty=<option> to handle empty patches, 2021-12-09).

git-cherry-pick(1), on the other hand, only supports two of the three
possiblities: Keep the redundant commits via `--keep-redundant-commits`,
or have the cherry-pick fail by not specifying that option. There is no
way to automatically drop redundant commits.

In order to bring git-cherry-pick(1) more in-line with git-rebase(1) and
git-am(1), this commit adds an `--empty` option to git-cherry-pick(1). It
has the same three options (keep, drop, and stop), and largely behaves
the same. The notable difference is that for git-cherry-pick(1), the
default will be `stop`, which maintains the current behavior when the
option is not specified.

Like the existing `--keep-redundant-commits`, `--empty=keep` will imply
`--allow-empty`.

The `--keep-redundant-commits` option will be documented as a deprecated
synonym of `--empty=keep`, and will be supported for backwards
compatibility for the time being.

Signed-off-by: Brian Lyles <brianmlyles@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/git-cherry-pick.txt | 30 +++++++++++++++++++------
 builtin/revert.c                  | 37 ++++++++++++++++++++++++++++++-
 sequencer.c                       |  6 +++++
 t/t3505-cherry-pick-empty.sh      | 37 ++++++++++++++++++++++++++++++-
 t/t3510-cherry-pick-sequence.sh   | 32 ++++++++++++++++++++++++++
 5 files changed, 133 insertions(+), 9 deletions(-)

diff --git a/Documentation/git-cherry-pick.txt b/Documentation/git-cherry-pick.txt
index fdcad3d200..81ace900fc 100644
--- a/Documentation/git-cherry-pick.txt
+++ b/Documentation/git-cherry-pick.txt
@@ -131,20 +131,36 @@ effect to your index in a row.
 	even without this option.  Note also, that use of this option only
 	keeps commits that were initially empty (i.e. the commit recorded the
 	same tree as its parent).  Commits which are made empty due to a
-	previous commit are dropped.  To force the inclusion of those commits
-	use `--keep-redundant-commits`.
+	previous commit will cause the cherry-pick to fail.  To force the
+	inclusion of those commits, use `--empty=keep`.
 
 --allow-empty-message::
 	By default, cherry-picking a commit with an empty message will fail.
 	This option overrides that behavior, allowing commits with empty
 	messages to be cherry picked.
 
+--empty=(drop|keep|stop)::
+	How to handle commits being cherry-picked that are redundant with
+	changes already in the current history.
++
+--
+`drop`;;
+	The commit will be dropped.
+`keep`;;
+	The commit will be kept. Implies `--allow-empty`.
+`stop`;;
+	The cherry-pick will stop when the commit is applied, allowing
+	you to examine the commit. This is the default behavior.
+--
++
+Note that `--empty=drop` and `--empty=stop` only specify how to handle a
+commit that was not initially empty, but rather became empty due to a previous
+commit. Commits that were initially empty will still cause the cherry-pick to
+fail unless one of `--empty=keep` or `--allow-empty` are specified.
++
+
 --keep-redundant-commits::
-	If a commit being cherry picked duplicates a commit already in the
-	current history, it will become empty.  By default these
-	redundant commits cause `cherry-pick` to stop so the user can
-	examine the commit. This option overrides that behavior and
-	creates an empty commit object.  Implies `--allow-empty`.
+	Deprecated synonym for `--empty=keep`.
 
 --strategy=<strategy>::
 	Use the given merge strategy.  Should only be used once.
diff --git a/builtin/revert.c b/builtin/revert.c
index a1936ef70e..53935d2c68 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -43,6 +43,31 @@ static const char * const *revert_or_cherry_pick_usage(struct replay_opts *opts)
 	return opts->action == REPLAY_REVERT ? revert_usage : cherry_pick_usage;
 }
 
+enum empty_action {
+	EMPTY_COMMIT_UNSPECIFIED = -1,
+	STOP_ON_EMPTY_COMMIT,      /* output errors and stop in the middle of a cherry-pick */
+	DROP_EMPTY_COMMIT,         /* skip with a notice message */
+	KEEP_EMPTY_COMMIT,         /* keep recording as empty commits */
+};
+
+static int parse_opt_empty(const struct option *opt, const char *arg, int unset)
+{
+	int *opt_value = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
+	if (!strcmp(arg, "stop"))
+		*opt_value = STOP_ON_EMPTY_COMMIT;
+	else if (!strcmp(arg, "drop"))
+		*opt_value = DROP_EMPTY_COMMIT;
+	else if (!strcmp(arg, "keep"))
+		*opt_value = KEEP_EMPTY_COMMIT;
+	else
+		return error(_("invalid value for '%s': '%s'"), "--empty", arg);
+
+	return 0;
+}
+
 static int option_parse_m(const struct option *opt,
 			  const char *arg, int unset)
 {
@@ -85,6 +110,7 @@ static int run_sequencer(int argc, const char **argv, const char *prefix,
 	const char * const * usage_str = revert_or_cherry_pick_usage(opts);
 	const char *me = action_name(opts);
 	const char *cleanup_arg = NULL;
+	enum empty_action empty_opt = EMPTY_COMMIT_UNSPECIFIED;
 	int cmd = 0;
 	struct option base_options[] = {
 		OPT_CMDMODE(0, "quit", &cmd, N_("end revert or cherry-pick sequence"), 'q'),
@@ -114,7 +140,10 @@ static int run_sequencer(int argc, const char **argv, const char *prefix,
 			OPT_BOOL(0, "ff", &opts->allow_ff, N_("allow fast-forward")),
 			OPT_BOOL(0, "allow-empty", &opts->allow_empty, N_("preserve initially empty commits")),
 			OPT_BOOL(0, "allow-empty-message", &opts->allow_empty_message, N_("allow commits with empty messages")),
-			OPT_BOOL(0, "keep-redundant-commits", &opts->keep_redundant_commits, N_("keep redundant, empty commits")),
+			OPT_BOOL(0, "keep-redundant-commits", &opts->keep_redundant_commits, N_("deprecated: use --empty=keep instead")),
+			OPT_CALLBACK_F(0, "empty", &empty_opt, "(stop|drop|keep)",
+				       N_("how to handle commits that become empty"),
+				       PARSE_OPT_NONEG, parse_opt_empty),
 			OPT_END(),
 		};
 		options = parse_options_concat(options, cp_extra);
@@ -134,6 +163,11 @@ static int run_sequencer(int argc, const char **argv, const char *prefix,
 	prepare_repo_settings(the_repository);
 	the_repository->settings.command_requires_full_index = 0;
 
+	if (opts->action == REPLAY_PICK) {
+		opts->drop_redundant_commits = (empty_opt == DROP_EMPTY_COMMIT);
+		opts->keep_redundant_commits = opts->keep_redundant_commits || (empty_opt == KEEP_EMPTY_COMMIT);
+	}
+
 	/* implies allow_empty */
 	if (opts->keep_redundant_commits)
 		opts->allow_empty = 1;
@@ -168,6 +202,7 @@ static int run_sequencer(int argc, const char **argv, const char *prefix,
 				"--rerere-autoupdate", opts->allow_rerere_auto == RERERE_AUTOUPDATE,
 				"--no-rerere-autoupdate", opts->allow_rerere_auto == RERERE_NOAUTOUPDATE,
 				"--keep-redundant-commits", opts->keep_redundant_commits,
+				"--empty", empty_opt != EMPTY_COMMIT_UNSPECIFIED,
 				NULL);
 	}
 
diff --git a/sequencer.c b/sequencer.c
index 1964977545..879b8ba2c0 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -2932,6 +2932,9 @@ static int populate_opts_cb(const char *key, const char *value,
 	else if (!strcmp(key, "options.allow-empty-message"))
 		opts->allow_empty_message =
 			git_config_bool_or_int(key, value, ctx->kvi, &error_flag);
+	else if (!strcmp(key, "options.drop-redundant-commits"))
+		opts->drop_redundant_commits =
+			git_config_bool_or_int(key, value, ctx->kvi, &error_flag);
 	else if (!strcmp(key, "options.keep-redundant-commits"))
 		opts->keep_redundant_commits =
 			git_config_bool_or_int(key, value, ctx->kvi, &error_flag);
@@ -3476,6 +3479,9 @@ static int save_opts(struct replay_opts *opts)
 	if (opts->allow_empty_message)
 		res |= git_config_set_in_file_gently(opts_file,
 				"options.allow-empty-message", "true");
+	if (opts->drop_redundant_commits)
+		res |= git_config_set_in_file_gently(opts_file,
+				"options.drop-redundant-commits", "true");
 	if (opts->keep_redundant_commits)
 		res |= git_config_set_in_file_gently(opts_file,
 				"options.keep-redundant-commits", "true");
diff --git a/t/t3505-cherry-pick-empty.sh b/t/t3505-cherry-pick-empty.sh
index 61f91aaa0a..9748443530 100755
--- a/t/t3505-cherry-pick-empty.sh
+++ b/t/t3505-cherry-pick-empty.sh
@@ -84,7 +84,7 @@ test_expect_success 'cherry-pick a commit that becomes no-op (prep)' '
 	git commit -m "add file2 on the side"
 '
 
-test_expect_success 'cherry-pick a no-op without --keep-redundant' '
+test_expect_success 'cherry-pick a no-op with neither --keep-redundant nor --empty' '
 	git reset --hard &&
 	git checkout fork^0 &&
 	test_must_fail git cherry-pick main
@@ -113,4 +113,39 @@ test_expect_success '--keep-redundant-commits is incompatible with operations' '
 	git cherry-pick --abort
 '
 
+test_expect_success '--empty is incompatible with operations' '
+	test_must_fail git cherry-pick HEAD 2>output &&
+	test_grep "The previous cherry-pick is now empty" output &&
+	test_must_fail git cherry-pick --empty=stop --continue 2>output &&
+	test_grep "fatal: cherry-pick: --empty cannot be used with --continue" output &&
+	test_must_fail git cherry-pick --empty=stop --skip 2>output &&
+	test_grep "fatal: cherry-pick: --empty cannot be used with --skip" output &&
+	test_must_fail git cherry-pick --empty=stop --abort 2>output &&
+	test_grep "fatal: cherry-pick: --empty cannot be used with --abort" output &&
+	test_must_fail git cherry-pick --empty=stop --quit 2>output &&
+	test_grep "fatal: cherry-pick: --empty cannot be used with --quit" output &&
+	git cherry-pick --abort
+'
+
+test_expect_success 'cherry-pick a no-op with --empty=stop' '
+	git reset --hard &&
+	git checkout fork^0 &&
+	test_must_fail git cherry-pick --empty=stop main 2>output &&
+	test_grep "The previous cherry-pick is now empty" output
+'
+
+test_expect_success 'cherry-pick a no-op with --empty=drop' '
+	git reset --hard &&
+	git checkout fork^0 &&
+	git cherry-pick --empty=drop main &&
+	test_commit_message HEAD -m "add file2 on the side"
+'
+
+test_expect_success 'cherry-pick a no-op with --empty=keep' '
+	git reset --hard &&
+	git checkout fork^0 &&
+	git cherry-pick --empty=keep main &&
+	test_commit_message HEAD -m "add file2 on main"
+'
+
 test_done
diff --git a/t/t3510-cherry-pick-sequence.sh b/t/t3510-cherry-pick-sequence.sh
index 72020a51c4..7eb52b12ed 100755
--- a/t/t3510-cherry-pick-sequence.sh
+++ b/t/t3510-cherry-pick-sequence.sh
@@ -90,6 +90,38 @@ test_expect_success 'cherry-pick persists opts correctly' '
 	test_cmp expect actual
 '
 
+test_expect_success 'cherry-pick persists --empty=stop correctly' '
+	pristine_detach yetanotherpick &&
+	# Picking `anotherpick` forces a conflict so that we stop. That
+	# commit is then skipped, after which we pick `yetanotherpick`
+	# while already on `yetanotherpick` to cause an empty commit
+	test_must_fail git cherry-pick --empty=stop anotherpick yetanotherpick &&
+	test_must_fail git cherry-pick --skip 2>msg &&
+	test_grep "The previous cherry-pick is now empty" msg &&
+	rm msg &&
+	git cherry-pick --abort
+'
+
+test_expect_success 'cherry-pick persists --empty=drop correctly' '
+	pristine_detach yetanotherpick &&
+	# Picking `anotherpick` forces a conflict so that we stop. That
+	# commit is then skipped, after which we pick `yetanotherpick`
+	# while already on `yetanotherpick` to cause an empty commit
+	test_must_fail git cherry-pick --empty=drop anotherpick yetanotherpick &&
+	git cherry-pick --skip &&
+	test_cmp_rev yetanotherpick HEAD
+'
+
+test_expect_success 'cherry-pick persists --empty=keep correctly' '
+	pristine_detach yetanotherpick &&
+	# Picking `anotherpick` forces a conflict so that we stop. That
+	# commit is then skipped, after which we pick `yetanotherpick`
+	# while already on `yetanotherpick` to cause an empty commit
+	test_must_fail git cherry-pick --empty=keep anotherpick yetanotherpick &&
+	git cherry-pick --skip &&
+	test_cmp_rev yetanotherpick HEAD^
+'
+
 test_expect_success 'revert persists opts correctly' '
 	pristine_detach initial &&
 	# to make sure that the session to revert a sequence