[PATCH] signature-format.txt: Note SSH and X.509 signature delimiters

[Gwyneth Morgan <gwymor@tilde.club>]

This document only explained PGP signatures, but Git now supports X.509
and SSH signatures.

Signed-off-by: Gwyneth Morgan <gwymor@tilde.club>
---
 Documentation/technical/signature-format.txt | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/Documentation/technical/signature-format.txt b/Documentation/technical/signature-format.txt
index 166721be6f..c148d4c750 100644
--- a/Documentation/technical/signature-format.txt
+++ b/Documentation/technical/signature-format.txt
@@ -9,9 +9,22 @@ is about to create an object or transaction determines a payload from that,
 calls gpg to obtain a detached signature for the payload (`gpg -bsa`) and
 embeds the signature into the object or transaction.
 
-Signatures always begin with `-----BEGIN PGP SIGNATURE-----`
-and end with `-----END PGP SIGNATURE-----`, unless gpg is told to
-produce RFC1991 signatures which use `MESSAGE` instead of `SIGNATURE`.
+Signatures always begin and end with a delimiter, which differs
+depending on signature type.
+
+PGP::
+	Signatures begin with `-----BEGIN PGP SIGNATURE-----` and end
+	with `-----END PGP SIGNATURE-----`, unless gpg is told to
+	produce RFC1991 signatures which use `MESSAGE` instead of
+	`SIGNATURE`.
+
+SSH::
+	Signatures begin with `-----BEGIN SSH SIGNATURE-----` and end
+	with `-----END SSH SIGNATURE-----`.
+
+X.509::
+	Signatures begin with `-----BEGIN SIGNED MESSAGE-----` and end
+	with `-----END SIGNED MESSAGE-----`.
 
 Signatures sometimes appear as a part of the normal payload
 (e.g. a signed tag has the signature block appended after the payload