[PATCH v4 1/3] sequencer: fix gpg option passed to merge subcommand

[Samuel Čavoj <samuel@xxxxxxxxx>]

When performing a rebase with --rebase-merges using either a custom
strategy specified with -s or an octopus merge, and at the same time
having gpgsign enabled (either rebase -S or config commit.gpgsign), the
operation would fail on making the merge commit. Instead of "-S%s" with
the key id substituted, only the bare key id would get passed to the
underlying merge command, which tried to interpret it as a ref.

Fix the issue and add test cases as suggested by Johannes Schindelin and
Junio C Hamano.

Signed-off-by: Samuel Čavoj <samuel@xxxxxxxxx>
---
changed v3 -> v4:
    - added explicit test_unconfig to test case
    - use git config instead of test_config
    - added one more test case
---
 sequencer.c                |  2 +-
 t/t3435-rebase-gpg-sign.sh | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/sequencer.c b/sequencer.c
index 00acb12496..88ccff4838 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -3677,7 +3677,7 @@ static int do_merge(struct repository *r,
 		strvec_push(&cmd.args, "-F");
 		strvec_push(&cmd.args, git_path_merge_msg(r));
 		if (opts->gpg_sign)
-			strvec_push(&cmd.args, opts->gpg_sign);
+			strvec_pushf(&cmd.args, "-S%s", opts->gpg_sign);
 
 		/* Add the tips to be merged */
 		for (j = to_merge; j; j = j->next)
diff --git a/t/t3435-rebase-gpg-sign.sh b/t/t3435-rebase-gpg-sign.sh
index b47c59c190..a2b7625707 100755
--- a/t/t3435-rebase-gpg-sign.sh
+++ b/t/t3435-rebase-gpg-sign.sh
@@ -68,4 +68,25 @@ test_expect_failure 'rebase -p --no-gpg-sign override commit.gpgsign' '
 	test_must_fail git verify-commit HEAD
 '
 
+test_expect_success 'rebase -r, merge strategy, --gpg-sign will sign commit' '
+	git reset --hard merged &&
+	test_unconfig commit.gpgsign &&
+	git rebase -fr --gpg-sign -s resolve --root &&
+	git verify-commit HEAD
+'
+
+test_expect_success 'rebase -r, merge strategy, commit.gpgsign=true will sign commit' '
+	git reset --hard merged &&
+	git config commit.gpgsign true &&
+	git rebase -fr -s resolve --root &&
+	git verify-commit HEAD
+'
+
+test_expect_success 'rebase -r, merge strategy, commit.gpgsign=false --gpg-sign will sign commit' '
+	git reset --hard merged &&
+	git config commit.gpgsign false &&
+	git rebase -fr --gpg-sign -s resolve --root &&
+	git verify-commit HEAD
+'
+
 test_done
-- 
2.28.0