What is the "key" (prefix) for versions extracted from filename by s3 resource?

[anentropic]

https://concourse-ci.org/managing-resources.html#fly-pin-resource

To pin a resource to a specific version of that resource, run:
$ fly -t example pin-resource --resource my-pipeline/my-resource \ --version ref:bceaf
Note that the version needs to be provided as a key-value pair. For the git resource the ref: prefix is used while the registry resource might use digest as a prefix like digest:sha256:94be7d7b.

So if we're using s3 resource to watch a file, and the version is extracted from the filename, what is the key prefix for this version?

[anentropic]

well I found fly resource-versions and was able to determine the answer

our resource def looks like:

- name: name-of-bucket-resource
  type: s3-iam
  source:
    bucket: us-east-1-some-app-bucket
    regexp: blah/blah/blah/(v.*)
    region_name: us-east-1

and the filenames in the bucket look like v1.0.23477-dfc0bed61

from what it says in the readme I was expecting the version to be the captured group i.e. v1.0.23477-dfc0bed61

instead the version is the full path blah/blah/blah/v1.0.23477-dfc0bed61

and the prefix is path

so we can pin the resource versions like:

fly -t example pin-resource \
  --resource my-pipeline/name-of-bucket-resource \
  --version path:blah/blah/blah/v1.0.23477-dfc0bed61