alertmanager: upgrade to 0.20.0
We can drop this patch as a similar fix landed in this release.
alertmanager: add Message-ID patch
alertmanager: add alertmanager_args to initd/confd
Many alertmanager options are only configurable at the command line.
alertmanager: correct daemon path
alertmanager: checkpath to ensure storage dir
The last commit was a red herring, the actual problem is that the
storage dir was not there.
alertmanager: remove storage path option
This was a copy+paste error from prometheus.
alertmanager: update checksums
alertmanager: normalize initd/confd
Move prometheus packages into main repo