Enhance HTTP support

Setting REPO_CURL_VERBOSE=1 in the environment will register a debug
level HTTPHandler on the urllib2 library, showing HTTP requests and
responses on the stderr channel of repo.

During any HTTP or HTTPS request created inside of the repo process,
a custom User-Agent header is now defined:

  User-Agent: git-repo/1.7.5 (Linux) git/1.7.7 Python/2.6.5

Change-Id: Ia5026fb1e1500659bd2af27416d85e205048bf26
Signed-off-by: Shawn O. Pearce <sop@google.com>
2 files changed