Add support for fetching helmfiles as .tar.gz

[mseiwald]

Fixes #1842

Example:

helmfiles:
  - path: https://host/path@helmfile.yaml.tar.gz

[mseiwald]

@mumoshu First super simplistic implementation but it actually works. Feedback appreciated.

[mumoshu]

@mseiwald Hey! Thanks for your effort.

I gave it a shot and to me this doesn't work:

helmfiles:
  - path: https://github.com/helmfile/testdata/releases/download/test@helmfile-test.tar.gz

But this one works:

helmfiles:
  - path: https://github.com/helmfile/testdata/releases/download/test/helmfile-test.tar.gz@

Probably you expect the tarball to contain a single directory named $BASE where your tarball is named $BASE.tar.gz, right? Mine contains helmfile.yaml at the root level of the archive.

I'd say the latter form is better in respect to the meaning of @ in helmfile, whose right part refers to a path in the downloaded directory.

That said, can you verify that it works with `helmfiles:

• path: https://host/path/helmfile.yaml.tar.gz@the-dir-contained-in-your-tarball` for your tarball?

[mseiwald]

@mumoshu Actually it works like this:

helmfile.yaml.tar.gz needs to contain a helmfile.yaml at the root level of the archive. (everything before .tar.gz is supposed to be the path of the "entry level" helmfile.

So in your first example you probably just need to rename the tar file.

Would that work for you?

[mseiwald]

I just realized that your suggestion already works with the latest unmodified helmfile. 🤦

helmfiles:
  - path: https://host/path/to/helmfile.yaml.tar.gz@helmfile.yaml

I'll just close this PR then since I agree that this is also the clearest syntax. Thanks anyway. :)