Provide default working config for artifacts

[stuartnelson3]

Fixes #484

[brian-brazil]

👍

[mxinden]

@stuartnelson3 @brian-brazil What is the reasoning for changing WORKDIR from /alertmanager to /etc/alertmanager? Prometheus uses /prometheus. I would expect etc for configuration files, but not for alerting data. If not /alertmanager, maybe /var/alertmanager?

This came up here: #1433

[mxinden]

Suggested fix https://github.com/prometheus/alertmanager/pull/1435/files

[discordianfish]

Yeah that broke our setup too. It's also not mentioned in the changelog.

[mxinden]

@discordianfish yes, sorry about the missing changelog entry. I fixed that and updated CHANGELOG.md in both release and master branch.

Once @stuartnelson3 is back, he can probably give us more details here for the initial change.

[stuartnelson3]

A bit sheepishly, I admit that changing the WORKDIR was so that I didn't have to add the --config.file flag to the invocation. Feel free to change it back, just remember to specify the config location.

[stuartnelson3]

@mxinden ^

[mxinden]

@stuartnelson3 ok. Let's move this discussion to #1435 then.