ssh signing: support non ssh-* keytypes

The user.signingKey config for ssh signing supports either a path to a
file containing the key or for the sake of convenience a literal string
with the ssh public key. To differentiate between those two cases we
check if the first few characters contain "ssh-" which is unlikely to be
the start of a path. ssh supports other key types which are not prefixed
with "ssh-" and will currently be treated as a file path and therefore
fail to load. To remedy this we move the prefix check into its own
function and introduce the prefix `key::` for literal ssh keys. This way
we don't need to add new key types when they become available. The
existing `ssh-` prefix is retained for compatibility with current user
configs but removed from the official documentation to discourage its
use.

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

1 files changed, 23 insertions, 1 deletions

diff --git a/t/t7528-signed-commit-ssh.sh b/t/t7528-signed-commit-ssh.sh
index badf3ed320..455eafa15c 100755
--- a/t/t7528-signed-commit-ssh.sh
+++ b/t/t7528-signed-commit-ssh.sh
@@ -73,7 +73,29 @@ test_expect_success GPGSSH 'create signed commits' '
 	git tag eleventh-signed $(cat oid) &&
 	echo 12 | git commit-tree --gpg-sign="${GPGSSH_KEY_UNTRUSTED}" HEAD^{tree} >oid &&
 	test_line_count = 1 oid &&
-	git tag twelfth-signed-alt $(cat oid)
+	git tag twelfth-signed-alt $(cat oid) &&
+
+	echo 13>file && test_tick && git commit -a -m thirteenth -S"${GPGSSH_KEY_ECDSA}" &&
+	git tag thirteenth-signed-ecdsa
+'
+
+test_expect_success GPGSSH 'sign commits using literal public keys with ssh-agent' '
+	test_when_finished "test_unconfig commit.gpgsign" &&
+	test_config gpg.format ssh &&
+	eval $(ssh-agent) &&
+	test_when_finished "kill ${SSH_AGENT_PID}" &&
+	ssh-add "${GPGSSH_KEY_PRIMARY}" &&
+	echo 1 >file && git add file &&
+	git commit -a -m rsa-inline -S"$(cat "${GPGSSH_KEY_PRIMARY}.pub")" &&
+	echo 2 >file &&
+	test_config user.signingkey "$(cat "${GPGSSH_KEY_PRIMARY}.pub")" &&
+	git commit -a -m rsa-config -S &&
+	ssh-add "${GPGSSH_KEY_ECDSA}" &&
+	echo 3 >file &&
+	git commit -a -m ecdsa-inline -S"key::$(cat "${GPGSSH_KEY_ECDSA}.pub")" &&
+	echo 4 >file &&
+	test_config user.signingkey "key::$(cat "${GPGSSH_KEY_ECDSA}.pub")" &&
+	git commit -a -m ecdsa-config -S
 '
 
 test_expect_success GPGSSH 'verify and show signatures' '