Document how to specify multiple excludeMetrics

The documentation mentions multiple patterns can be given by repeating
the `excludeMetrics` setting but it was unclear to me how to proceed.

The setting is fetched using a getStringList() which comes from jgit and
indeed one just need to repeat it. An example makes it clearer.

I also thought the matching was to be done against the metric names
exposed to Prometheus, but it is instead done against the Gerrit metric
name (`/` separated).

The doc mentions the matching is done on the whole key, document that it
is internally using `regex.Matcher.matches()` (and not `lookingAt()`
which matches at the start of the subject).  The multiple values
example does use a lead carret '^' which indicates matching at the start
of metric name has to be set explicitly.

Change-Id: I89fd2d4bb6523446ba54f741767336f907c800ac
1 file changed
tree: bd9f3ee5edb35a78ffb090ed5236054cfcc20d76
  1. BUILD
  2. external_plugin_deps.bzl
  3. pom.xml
  4. src/