vendor: remove vendor ;)

[stevvooe]

The current vendoring setup makes it difficult for new developers to get started on the repository. It seems to be this way to address the problems with adoption across the Docker and Moby repositories. At this point, many of those issues seem to be behind us so it's worth a try again to make this project simpler to work on.

- What I did

Removed vendoring. I did it with a hammer, so we might need to make some repairs.

- How I did it

With a hammer. 🔨

- How to verify it

We should see CI build as normal. Downstream tests, such as moby, should pass as normal.

There were some areas that were using the term "vendor" in a plugin context. We should see NO regressions in that behavior.

- A picture of a cute animal (not mandatory but encouraged)

[stevvooe]

We might want to include #4228 as part of this.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 59.27%. Comparing base (77a8a8c) to head (4fd1866).

Additional details and impacted files

@@ Coverage Diff @@## master #5856 +/- ##
==========================================
- Coverage 59.30% 59.27% -0.03% 
==========================================
Files 353 353 Lines 29694 29694 ==========================================
- Hits 17609 17601 -8 - Misses 11104 11113 +9 + Partials 981 980 -1 

[thaJeztah]

not LGTM - this breaks the release pipeline, among others.

[stevvooe]

this breaks the release pipeline, among others.

Ok, how do we do this so it doesn't break the release pipeline?

[laurazard]

I assume that by "remove vendoring" what this does is "migrate to using go modules" – having a go.mod at the root of the repo means that we're opting into a whole new contract, and potentially impacts how future development can be done, as well as all downstream consumers of the CLI, so it should definitely not be done lightly.

[stevvooe]

@laurazard I think the primary issue here is the current setup makes it harder to contribute to cli and I thought I could solve that. Unfortunately, I underestimated how broken v2+ Go modules actually are and it seems like this will be a huge amount of work to get there. I was unable to mock out a solution to get the tags right in my fork and make this actually work.

Docker cli is an easy build, so this is a bit disappointing. I'll close this out and let the maintainers figure it out.