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>
-----------------