keychain: add page (#7583)

pages/common/keychain.md

@@ -0,0 +1,24 @@
+# keychain
+
+> Re-use ssh-agent and/or gpg-agent between logins.
+> More information: <http://funtoo.org/Keychain>.
+
+- Check for a running ssh-agent, and start one if needed:
+
+`keychain`
+
+- Also check for gpg-agent:
+
+`keychain --agents "{{gpg,ssh}}"`
+
+- List signatures of all active keys:
+
+`keychain --list`
+
+- List fingerprints of all active keys:
+
+`keychain --list-fp`
+
+- Add a timeout for identities added to the agent, in minutes:
+
+`keychain --timeout {{minutes}}`