S3 args are passed to head-object call

[mogopz]

Hi, In your README you mention that the args argument gets passed to the s3 cp command but in the code it's also being passed to the aws s3api head-object command.

This breaks a lot of arguments that someone might want to potentially pass (in my case --acl) since the two commands don't share the same options. For example when I try to set --acl the cache plugin fails once it tries to check for an existing cache:

usage: aws [options] <command> <subcommand> [<subcommand> ...] [parameters]
--
  | To see help text, you can run:
  |  
  | aws help
  | aws <command> help
  | aws <command> <subcommand> help
  |  
  | Unknown options: --acl, bucket-owner-full-control

I'm happy to open a PR to fix this if you let me know how you'd prefer to handle this. The PR that added custom args to the head-object command mentions needing it so they can set the endpoint, but that's already configurable with the endpoint argument so I think it makes the most sense to just remove the custom args from the head-object call.

[gencer]

endpoint can be separately defined in yaml and it has a special key, however, it is still appended to $BK_AWS_ARGS which is piped to aws s3api head-object just like s3 cp command. See: https://github.com/gencer/cache-buildkite-plugin/blob/17ee0f78000acc59ef081aeda95bae38b75e10a3/lib/backends/s3.bash#L51

What we are going to do here is to use separate variable to hold pre-defined keys and only pass this variable to head-object and for other calls we will merge it with $BK_AWS_ARGS.

However, If you are intend to work on this PR, please take above into consideration.

[mogopz]

Thanks @gencer, I've opened a PR - let me know what you think

[gencer]

Thanks @mogggggg for this great PR. I've gone ahead and merged.

Will release a new version soon. 🚀🎉

[gencer]

Released as v2.4.9 🎉