rebase.c: honour --no-gpg-sign

Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-rebase.txt

@@ -354,9 +354,12 @@ See also INCOMPATIBLE OPTIONS below.
 
 -S[<keyid>]::
 --gpg-sign[=<keyid>]::
+--no-gpg-sign::
 	GPG-sign commits. The `keyid` argument is optional and
 	defaults to the committer identity; if specified, it must be
-	stuck to the option without a space.
+	stuck to the option without a space. `--no-gpg-sign` is useful to
+	countermand both `commit.gpgSign` configuration variable, and
+	earlier `--gpg-sign`.
 
 -q::
 --quiet::

builtin/rebase.c

@@ -1592,6 +1592,9 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 
 	options.allow_empty_message = 1;
 	git_config(rebase_config, &options);
+	/* options.gpg_sign_opt will be either "-S" or NULL */
+	gpg_sign = options.gpg_sign_opt ? "" : NULL;
+	FREE_AND_NULL(options.gpg_sign_opt);
 
 	if (options.use_legacy_rebase ||
 	    !git_env_bool("GIT_TEST_REBASE_USE_BUILTIN", -1))
@@ -1822,10 +1825,8 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 	if (options.empty != EMPTY_UNSPECIFIED)
 		imply_merge(&options, "--empty");
 
-	if (gpg_sign) {
-		free(options.gpg_sign_opt);
+	if (gpg_sign)
 		options.gpg_sign_opt = xstrfmt("-S%s", gpg_sign);
-	}
 
 	if (exec.nr) {
 		int i;

t/t3435-rebase-gpg-sign.sh

@@ -0,0 +1,71 @@
+#!/bin/sh
+#
+# Copyright (c) 2020 Doan Tran Cong Danh
+#
+
+test_description='test rebase --[no-]gpg-sign'
+
+. ./test-lib.sh
+. "$TEST_DIRECTORY/lib-rebase.sh"
+. "$TEST_DIRECTORY/lib-gpg.sh"
+
+if ! test_have_prereq GPG
+then
+	skip_all='skip all test rebase --[no-]gpg-sign, gpg not available'
+	test_done
+fi
+
+test_rebase_gpg_sign () {
+	local must_fail= will=will fake_editor=
+	if test "x$1" = "x!"
+	then
+		must_fail=test_must_fail
+		will="won't"
+		shift
+	fi
+	conf=$1
+	shift
+	test_expect_success "rebase $* with commit.gpgsign=$conf $will sign commit" "
+		git reset two &&
+		git config commit.gpgsign $conf &&
+		set_fake_editor &&
+		FAKE_LINES='r 1 p 2' git rebase --force-rebase --root $* &&
+		$must_fail git verify-commit HEAD^ &&
+		$must_fail git verify-commit HEAD
+	"
+}
+
+test_expect_success 'setup' '
+	test_commit one &&
+	test_commit two &&
+	test_must_fail git verify-commit HEAD &&
+	test_must_fail git verify-commit HEAD^
+'
+
+test_expect_success 'setup: merge commit' '
+	test_commit fork-point &&
+	git switch -c side &&
+	test_commit three &&
+	git switch master &&
+	git merge --no-ff side &&
+	git tag merged
+'
+
+test_rebase_gpg_sign ! false
+test_rebase_gpg_sign   true
+test_rebase_gpg_sign ! true  --no-gpg-sign
+test_rebase_gpg_sign ! true  --gpg-sign --no-gpg-sign
+test_rebase_gpg_sign   false --no-gpg-sign --gpg-sign
+test_rebase_gpg_sign   true  -i
+test_rebase_gpg_sign ! true  -i --no-gpg-sign
+test_rebase_gpg_sign ! true  -i --gpg-sign --no-gpg-sign
+test_rebase_gpg_sign   false -i --no-gpg-sign --gpg-sign
+
+test_expect_failure 'rebase -p --no-gpg-sign override commit.gpgsign' '
+	git reset --hard merged &&
+	git config commit.gpgsign true &&
+	git rebase -p --no-gpg-sign --onto=one fork-point master &&
+	test_must_fail git verify-commit HEAD
+'
+
+test_done