recognized by the receive-pack (push to server) process.
The 'ofs-delta' and 'side-band-64k' capabilities are sent and recognized
-by both upload-pack and receive-pack protocols.
+by both upload-pack and receive-pack protocols. The 'agent' capability
+may optionally be sent in both protocols.
All other capabilities are only recognized by the upload-pack (fetch
from server) process.
its base by position in pack rather than by an obj-id. That is, they can
send/read OBJ_OFS_DELTA (aka type 6) in a packfile.
+agent
+-----
+
+The server may optionally send a capability of the form `agent=X` to
+notify the client that the server is running version `X`. The client may
+optionally return its own agent string by responding with an `agent=Y`
+capability (but it MUST NOT do so if the server did not mention the
+agent capability). The `X` and `Y` strings may contain any printable
+ASCII characters except space (i.e., the byte range 32 < x < 127), and
+are typically of the form "package/version" (e.g., "git/1.8.3.1"). The
+agent strings are purely informative for statistics and debugging
+purposes, and MUST NOT be used to programatically assume the presence
+or absence of particular features.
+
shallow
-------