Display logs in a streaming fashion

JGit even on a fast workstation can only walk a few thousand commits
per second with rename detection on (and in a loaded server
environment it might be much slower). Loading a full page of 100 log
results for a file therefore might take many seconds.

Stream the output one log entry at a time so the page becomes
interactive slightly faster. Each HTTP chunk is a full <li></li> tag,
so browsers should be able to render incrementally.

This is much simpler than an alternative solution involving AJAX to
make multiple requests to the server, particularly in a multi-server
cluster environment where the client is not guaranteed to talk to the
same server (with the necessary RevWalk state in memory) on
consecutive requests.

Change-Id: I63c4bc655efd00453b6db60f333ba3dd5041e70a
6 files changed