Use custom error messages for Git-over-HTTP

Ensure clients see messages related to contributor agreement not
being activated even if they push over HTTP. These used to be put
into the server error log, but the new GitSmartHttpTools class in
JGit allows formatting it directly to the client.

Refactor other things like the server-level receive and upload
controls to also report a custom error message that matches with
the SSH version of the same code.

Change-Id: Idd35853198fcb3103ebb099bab185c0620573e0f
1 file changed