Clarify behaviour of plugin with no version/tag/commit specified

[smilin-desperado]

The plugin section of the documentation doesn't appear to define the behaviour of a plugin defined without a pinned hash.

If I define a plugin like this in a pipeline:

plugins:
  - myplugin:
      ...

it appears that the HEAD of the default branch is checked out.

If a new commit is subsequently pushed to the plugin's repo, running the pipeline again does not appear to check out the latest commit but instead the previously checked out one.

If this is expected behaviour, it might be clearer to specify it in the docs.

[plaindocs]

@pzeballos is this a caching thing do you know? Basically the plugin won't be reloaded on an agent that already has the plugin checked out, but a new agent spinning up would get the updated plugin? Sound right?

[pzeballos]

Hey @smilin-desperado! @plaindocs is right and this is a cache issue from our side and there was a lot of internal discussion about it; there’s quite a lot of complexity though, so we wanna make sure that we’re doing it right for our customers.

[smilin-desperado]

No worries @pzeballos I assumed it might have been related to caching. In my case, the fix was to simply specify the commit hash to pull in the latest changes of the plugin.
The confusion on my end was because of my incorrect assumption that not specifying a version/hash would always cause the HEAD of the default branch of the plugin to always be pulled

[plaindocs]

Roger that. I'll update those docs.