When a client does a git fetch over HTTP, workhorse performs an access
check based on the HTTP request header, then reads the entire request
body into a temporary file before handing off to Gitaly to service it.
However, the client has control over how long it takes to read the
request body. Since the Gitaly RPC only happens once the request body
is read, people can set up a connection before their access is revoked
and use it to gain access to code committed days or weeks later.

To resolve this, we place an overall limit of 10 minutes on receiving
the `upload-pack` request body. Since this is over HTTP, the client is
using the `--stateless-rpc` mode, and there is no negotiation between
client and server. The time limit is chosen fairly arbitrarily, but it
fits well with the existing 10MiB limit on request body size, implying
a transfer speed of just 17KiB/sec to be able to fill that buffer and
get a "request too large" error instead of "request too slow".

Workhorse does not expose the `upload-archive` endpoint directly to the
user; the client in that case is always gitlab-rails, so there is no
vulnerability there.

The `receive-pack` endpoint is theoretically vulnerable, but Gitaly
performs a second access check in the pre-receive hook which defeats
the attack, so no changes are needed.

The SSH endpoints are similarly vulnerable, but since those RPCs are
bidirectional, a different approach is needed.