Add support for transitive dependencies (needs).

[paichinger]

Problem

When using selectors in helmfile one can use the --include-needs parameter to also install the dependencies of the selected release(s). However, this doesn't work for transitive needs, only the direct needs of the specified releases will be included. The problem is described in more detail with an example here:
#1915

Solution

After conferring with @mumoshu we decided to introduce a new parameter called --include-transitive-needs, which will also include transitive needs. We deliberately decided to not change the behavior of --include-needs (even if including transitives might be the expected behavior for most users) to ensure backwards compatibility.

Notes

--include-transitive-needs will override any potential exclusions done by selectors or conditions. So even if you explicitly exclude a release via a selector it will still be part of the deployment in case it is a direct or transitive need of any of the specified releases.

Fixes #1915
Closes #1915

[mumoshu]

LGTM. Thanks a lot for your contribution! ☺️

I've left a few comments for potential problems- it would be awesome if you could confirm those and submit a follow-up PR! Thanks.

[dudicoco]

Hi @pjotre86 and @mumoshu,

As far as I know, needs has been broken for a few months now, see #1881.

Does this PR fix this bug?

[paichinger]

Hey @Hey @dudicoco !
Not sure, I never ran into the problem with needs described in #1881.

[dudicoco]

Hi @pjotre86,

Did you try to recreate the issue per the instructions in #1881?