Subject: [PATCH] cherry-pick: refuse cherry-pick sequence if index is dirty

From: "Tao Klerks via GitGitGadget" <[email-masked]>
Date: Tue, 23 May 2023 08:32:47 +0000

From: Tao Klerks <[email-masked]>

Cherry-pick, like merge or rebase, refuses to run when there are changes
in the index. However, if a cherry-pick sequence is requested, this
refusal happens "too late": when the cherry-pick sequence has already
started, and an "--abort" or "--quit" is needed to resume normal
operation.

Normally, when an operation is "in-progress" and you want to go back to
where you were before, "--abort" is the right thing to run. If you run
"git cherry-pick --abort" in this specific situation, however, your
staged changes are destroyed as part of the abort! Generally speaking,
the abort process assumes any changes in the index are part of the
operation to be aborted.

Add an earlier check in the cherry-pick sequence process to ensure that
the index is clean, reusing the already-generalized method used for
rebase. Also add a test.

Signed-off-by: Tao Klerks <[email-masked]>
---
    cherry-pick: refuse cherry-pick sequence if index is dirty
    
    I encountered this data-loss bug (performing normally-safe operations
    results in loss of local staged changes) while exploring
    largely-unrelated changes as per thread
    CAPMMpogFHnX2YPA4VmffmA0pku=[email-masked] on
    "git checkout --force", and on the possibility of supporting same-commit
    switch while preserving merge metadata.
    
    I believe it is best handled as a standalone issue, it looks like a
    simple bugfix to me, hence this separate patch.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1535%2FTaoK%2Ftao-cherry-pick-sequence-safety-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1535/TaoK/tao-cherry-pick-sequence-safety-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1535

 builtin/revert.c                |  2 +-
 sequencer.c                     | 14 +++++++++-----
 sequencer.h                     |  3 ++-
 t/t3510-cherry-pick-sequence.sh | 10 ++++++++++
 4 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/builtin/revert.c b/builtin/revert.c
index 0240ec8593b..91ebba38eaa 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -224,7 +224,7 @@ static int run_sequencer(int argc, const char **argv, const char *prefix,
 		return sequencer_rollback(the_repository, opts);
 	if (cmd == 's')
 		return sequencer_skip(the_repository, opts);
-	return sequencer_pick_revisions(the_repository, opts);
+	return sequencer_pick_revisions(the_repository, opts, me);
 }
 
 int cmd_revert(int argc, const char **argv, const char *prefix)
diff --git a/sequencer.c b/sequencer.c
index b553b49fbb6..9abea3b97fc 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -3162,7 +3162,7 @@ static int walk_revs_populate_todo(struct todo_list *todo_list,
 	return 0;
 }
 
-static int create_seq_dir(struct repository *r)
+static int create_seq_dir(struct repository *r, const char *requested_action)
 {
 	enum replay_action action;
 	const char *in_progress_error = NULL;
@@ -3194,6 +3194,9 @@ static int create_seq_dir(struct repository *r)
 				advise_skip ? "--skip | " : "");
 		return -1;
 	}
+	if (require_clean_work_tree(r, requested_action,
+				    _("Please commit or stash them."), 1, 1))
+		return -1;
 	if (mkdir(git_path_seq_dir(), 0777) < 0)
 		return error_errno(_("could not create sequencer directory '%s'"),
 				   git_path_seq_dir());
@@ -5169,7 +5172,8 @@ static int single_pick(struct repository *r,
 }
 
 int sequencer_pick_revisions(struct repository *r,
-			     struct replay_opts *opts)
+			     struct replay_opts *opts,
+			     const char *action)
 {
 	struct todo_list todo_list = TODO_LIST_INIT;
 	struct object_id oid;
@@ -5223,12 +5227,12 @@ int sequencer_pick_revisions(struct repository *r,
 
 	/*
 	 * Start a new cherry-pick/ revert sequence; but
-	 * first, make sure that an existing one isn't in
-	 * progress
+	 * first, make sure that the index is clean and that
+	 * an existing one isn't in progress.
 	 */
 
 	if (walk_revs_populate_todo(&todo_list, opts) ||
-			create_seq_dir(r) < 0)
+			create_seq_dir(r, action) < 0)
 		return -1;
 	if (repo_get_oid(r, "HEAD", &oid) && (opts->action == REPLAY_REVERT))
 		return error(_("can't revert as initial commit"));
diff --git a/sequencer.h b/sequencer.h
index 913a0f652d9..1b39325c52c 100644
--- a/sequencer.h
+++ b/sequencer.h
@@ -159,7 +159,8 @@ void todo_list_filter_update_refs(struct repository *r,
 /* Call this to setup defaults before parsing command line options */
 void sequencer_init_config(struct replay_opts *opts);
 int sequencer_pick_revisions(struct repository *repo,
-			     struct replay_opts *opts);
+			     struct replay_opts *opts,
+			     const char *action);
 int sequencer_continue(struct repository *repo, struct replay_opts *opts);
 int sequencer_rollback(struct repository *repo, struct replay_opts *opts);
 int sequencer_skip(struct repository *repo, struct replay_opts *opts);
diff --git a/t/t3510-cherry-pick-sequence.sh b/t/t3510-cherry-pick-sequence.sh
index 3b0fa66c33d..e8f4138bf89 100755
--- a/t/t3510-cherry-pick-sequence.sh
+++ b/t/t3510-cherry-pick-sequence.sh
@@ -47,6 +47,16 @@ test_expect_success 'cherry-pick persists data on failure' '
 	test_path_is_file .git/sequencer/opts
 '
 
+test_expect_success 'cherry-pick sequence refuses to run on dirty index' '
+	pristine_detach initial &&
+	touch localindexchange &&
+	git add localindexchange &&
+	echo picking &&
+	test_must_fail git cherry-pick initial..picked &&
+	test_path_is_missing .git/sequencer &&
+	test_must_fail git cherry-pick --abort
+'
+
 test_expect_success 'cherry-pick mid-cherry-pick-sequence' '
 	pristine_detach initial &&
 	test_must_fail git cherry-pick base..anotherpick &&

base-commit: 4a714b37029a4b63dbd22f7d7ed81f7a0d693680
-- 
gitgitgadget