Fix tar.gz support

[reegnz]

Fixes #285

[reegnz]

I haven't tried with other tar.gz files, but it definitely fixed the issue for this particular one of downloading a tar.gz of a github repo. Also the fix was inspired by this code in the go codebase: https://cs.opensource.google/go/x/build/+/2c66d68b:internal/untar/untar.go;l=34-139, particularly line 132 and 133.

[neil-hickey]

hey @reegnz , so this does appear to work on the surface. I think to really validate we are going to want some more e2e tests that cover each use-case. Is this something you would be able to contribute?

[reegnz]

@neil-hickey If you can point me to what exactly you'd like to see I can give it a go.

[joaopapereira]

I think we need something similar to https://github.com/carvel-dev/vendir/blob/develop/test/e2e/github_release_test.go but for HTTP workflow. We might need to standup a simple HTTP server and serve a tar.gz file from it to test it out.

[reegnz]

I think I'll just fetch a tar.gz from github (from this repo), that's one of those tar.gz-s what's causing the issue anyway, and that's the most life-like test.

[reegnz]

Pushed the e2e test (already had this in the making today, before the local http server idea).

[joaopapereira]

I left a comment. The linter is also failing do you mind giving it a check?

[reegnz]

@joaopapereira fixed.

[joaopapereira]

@reegnz you need to sign your commits 😄

[reegnz]

@joaopapereira rebased, added signoff to commits.

[joaopapereira]

LGTM

[kumaritanushree]

LGTM