will update the refs in one atomic transaction. Either all refs are
updated or none.
+push-options
+------------
+
+If the server sends the 'push-options' capability it is able to accept
+push options after the update commands have been sent, but before the
+packfile is streamed. If the pushing client requests this capability,
+the server will pass the options to the pre- and post- receive hooks
+that process this push request.
+
allow-tip-sha1-in-want
----------------------
send "want" lines with SHA-1s that exist at the server but are not
advertised by upload-pack.
+allow-reachable-sha1-in-want
+----------------------------
+
+If the upload-pack server advertises this capability, fetch-pack may
+send "want" lines with SHA-1s that exist at the server but are not
+advertised by upload-pack.
+
push-cert=<nonce>
-----------------