For ?zip compress the patch file text inside of a ZIP archive.
The inner file name is "commitsha1.diff". Modern UI shells on
Windows, Mac OS X and Linux make it easy to unpack the compressed
ZIP file to get access to the raw text.
For ?download a filename is suggested in the Content-Dispostion
response header, suggesting the browser to download the base64
encoded stream to the local drive as "commitsha1.diff.base64".
Encoding the patch is necessary to prevent XSS attacks made against
the Gerrit site. The ZIP wrapping does not allow an attacker to
make a valid Java applet; the filename ending in ".diff" is not
a valid Java class file name. The base64 wrapping can only be
treated as plain text by a browser as it does not contain HTML
special characters.
Change-Id: Ia4c41e51c5f57607c45e2588629a88b47e1d9d09
973f38bc4a