Rather than serving a static file, serve the PolyGerrit index HTML
document from a Soy template. In this way, the path to load PG
dependencies can be safely parameterized in two ways:
* If Gerrit is not running on the root of the domain (e.g. listening on
https://example.com/my-gerrit/) the path component of the Canonical
Web URL is used to load PG dependencies.
Instead of /elements/gr-app.js off the root of the domain it uses
/my-gerrit/elements/gr-app.js
* If the PolyGerrit static resources are to be served from a CDN rather
than the Gerrit WAR, the `cdnPath` config in the [gerrit] section can
be used.
For example, if the server config says ...
[gerrit]
cdnPath = http://my-cdn.com/pg/version/123
... then it uses the following style of path for PG dependencies.
http://my-cdn.com/pg/version/123/my-gerrit/elements/gr-app.js
If a CDN-path is configured, it supersedes subdirectories appearing
in the Canonical-Web-URL for this purpose.
Feature: Issue 5845
Change-Id: I2b2d704fe33c90ea2f2a2183fc79897642a48175
(cherry picked from commit 414659c792)
558a2afbd2