ssh signing: make fmt-merge-msg consider key lifetime

Set the payload_type for check_signature() when generating merge messages to
verify merged tags signatures key lifetimes.
Implements the same tests as for verify-commit.

Signed-off-by: Fabian Stelzer <fs@gigacodes.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

fmt-merge-msg.c

@@ -533,6 +533,7 @@ static void fmt_merge_msg_sigs(struct strbuf *out)
 		else {
 			buf = payload.buf;
 			len = payload.len;
+			sigc.payload_type = SIGNATURE_PAYLOAD_TAG;
 			sigc.payload = strbuf_detach(&payload, &sigc.payload_len);
 			if (check_signature(&sigc, sig.buf, sig.len) &&
 			    !sigc.output)

t/t6200-fmt-merge-msg.sh

@@ -91,6 +91,26 @@ test_expect_success GPGSSH 'created ssh signed commit and tag' '
 	git tag -s -u"${GPGSSH_KEY_UNTRUSTED}" -m signed-ssh-tag-msg-untrusted signed-untrusted-ssh-tag left
 '
 
+test_expect_success GPGSSH,GPGSSH_VERIFYTIME 'create signed tags with keys having defined lifetimes' '
+	test_when_finished "test_unconfig commit.gpgsign" &&
+	test_config gpg.format ssh &&
+	git checkout -b signed-expiry-ssh &&
+	touch file &&
+	git add file &&
+
+	echo expired >file && test_tick && git commit -a -m expired -S"${GPGSSH_KEY_EXPIRED}" &&
+	git tag -s -u "${GPGSSH_KEY_EXPIRED}" -m expired-signed expired-signed &&
+
+	echo notyetvalid >file && test_tick && git commit -a -m notyetvalid -S"${GPGSSH_KEY_NOTYETVALID}" &&
+	git tag -s -u "${GPGSSH_KEY_NOTYETVALID}" -m notyetvalid-signed notyetvalid-signed &&
+
+	echo timeboxedvalid >file && test_tick && git commit -a -m timeboxedvalid -S"${GPGSSH_KEY_TIMEBOXEDVALID}" &&
+	git tag -s -u "${GPGSSH_KEY_TIMEBOXEDVALID}" -m timeboxedvalid-signed timeboxedvalid-signed &&
+
+	echo timeboxedinvalid >file && test_tick && git commit -a -m timeboxedinvalid -S"${GPGSSH_KEY_TIMEBOXEDINVALID}" &&
+	git tag -s -u "${GPGSSH_KEY_TIMEBOXEDINVALID}" -m timeboxedinvalid-signed timeboxedinvalid-signed
+'
+
 test_expect_success 'message for merging local branch' '
 	echo "Merge branch ${apos}left${apos}" >expected &&
 
@@ -139,6 +159,44 @@ test_expect_success GPGSSH 'message for merging local tag signed by unknown ssh
 	! grep "${GPGSSH_BAD_SIGNATURE}" actual &&
 	grep "${GPGSSH_KEY_NOT_TRUSTED}" actual
 '
+
+test_expect_success GPGSSH,GPGSSH_VERIFYTIME 'message for merging local tag signed by expired ssh key' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	git checkout main &&
+	git fetch . expired-signed &&
+	git fmt-merge-msg <.git/FETCH_HEAD >actual &&
+	grep "^Merge tag ${apos}expired-signed${apos}" actual &&
+	! grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual
+'
+
+test_expect_success GPGSSH,GPGSSH_VERIFYTIME 'message for merging local tag signed by not yet valid ssh key' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	git checkout main &&
+	git fetch . notyetvalid-signed &&
+	git fmt-merge-msg <.git/FETCH_HEAD >actual &&
+	grep "^Merge tag ${apos}notyetvalid-signed${apos}" actual &&
+	! grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual
+'
+
+test_expect_success GPGSSH,GPGSSH_VERIFYTIME 'message for merging local tag signed by valid timeboxed ssh key' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	git checkout main &&
+	git fetch . timeboxedvalid-signed &&
+	git fmt-merge-msg <.git/FETCH_HEAD >actual &&
+	grep "^Merge tag ${apos}timeboxedvalid-signed${apos}" actual &&
+	grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual &&
+	! grep "${GPGSSH_BAD_SIGNATURE}" actual
+'
+
+test_expect_success GPGSSH,GPGSSH_VERIFYTIME 'message for merging local tag signed by invalid timeboxed ssh key' '
+	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
+	git checkout main &&
+	git fetch . timeboxedinvalid-signed &&
+	git fmt-merge-msg <.git/FETCH_HEAD >actual &&
+	grep "^Merge tag ${apos}timeboxedinvalid-signed${apos}" actual &&
+	! grep "${GPGSSH_GOOD_SIGNATURE_TRUSTED}" actual
+'
+
 test_expect_success 'message for merging external branch' '
 	echo "Merge branch ${apos}left${apos} of $(pwd)" >expected &&