Document JGit receive command size options

Document receive.maxCommandBytes and receive.maxCommandDiscardBytes,
which limit the receive-pack command block and the amount of command
data discarded after the limit is exceeded.

These options are JGit-specific and do not correspond to native Git
configuration options.

Change-Id: I4e5c0586960b13acb814ff3e6a9e17153fd25ede
diff --git a/Documentation/config-options.md b/Documentation/config-options.md
index 8a7012b..0b5a7f3 100644
--- a/Documentation/config-options.md
+++ b/Documentation/config-options.md
@@ -136,6 +136,9 @@
 | option           | default | git option | description                                                                                |
 |------------------|---------|------------|--------------------------------------------------------------------------------------------|
 | `receive.autogc` | `true`  | ✅ | Perform an automatic garbage collection after a receive-pack operation has been completed. |
+| `receive.maxCommandBytes` | `3 MiB` | ⃞ | Maximum number of bytes to read from the receive-pack command block before the pack data. If set to `0`, there is no limit. |
+| `receive.maxCommandDiscardBytes` | `-1` | ⃞ | Maximum number of command-block bytes to discard after `receive.maxCommandBytes` is exceeded, so JGit can report a side-band error before disconnecting. If set to `0`, there is no limit. If set to `-1`, JGit uses the larger of `3 * receive.maxCommandBytes` and `3 MiB`. |
+
 
 ## __repack__ options