Add an `alpine-latest` flavor to the helper image
Description
When we update the base image for the runner helper images users need to manually update their configuration to get the benefits. We don't do it automatically as those update can possibly be breaking changes.
The documentation states
The helper image has a few flavors:
alpine
,alpine3.12
,alpine3.13
,alpine3.14
,alpine3.15
, andubuntu
. Thealpine
flavor uses the same version asalpine3.12
.
Usually in docker image tags the absence of specific version details implies the latest version. For example the tag 3
for the alpine
image on dockerhub implies 3.15
(the latest), the tag 3.14
implies 3.14.3
(latest patch update), etc. However in this case the alpine
flavor follows the opposite pattern which could be counter-intuitive to some people.
Proposal
I suggest we introduce and document an alpine-latest
flavor that is the same as whatever the latest version is at that moment and would offer a way for customers who accept the stability trade-off to do so without having to manually keep an eye out of updates and manually change their config files.
Links to related issues and merge requests / references
Follow-up to https://gitlab.com/gitlab-org/gitlab-runner/-/issues/28847#note_846983577
/cc @DarrenEastman