chore(deps): update pre-commit hook renovatebot/pre-commit-hooks to v39.185.4

See merge request !59

Addresses the linked issue

fix(deps): update gomod-all

See merge request !60

chore(deps): update pre-commit hook renovatebot/pre-commit-hooks to v39.192.0

See merge request !61

Migrate to golangci-lint v2

See merge request !66

Update `pre-commit`

See merge request !67

With my own library because:

* I wanted something simpler: just something to parse args, not be the
  entire application
* I don't really agree with some of the choices made by `cli`,
  particularly, why should such a library suffer from any race
  conditions[1]

Other libraries considered:

* [1] but I didn't really like how values were handled
* [2] I appreciated a lot of this, but preferred actual objects over
  just using struct tags

Link: https://github.com/urfave/cli/issues/1699 [1]
Link: https://github.com/akamensky/argparse [2]
Link: https://github.com/jessevdk/go-flags [3]

Replace CLI parser

See merge request !70

chore(deps): update pre-commit hook renovatebot/pre-commit-hooks to v41

See merge request !68

chore(deps): update dependency matthewhughes/gitlab-ci-configurations to v0.11.0

See merge request !69

Required some config changes for `golangci-lint`[1]

Link: golangci-lint-defaults@0c06fa79 [1]

chore(deps): update pre-commit-all

See merge request !62

chore(deps): update pre-commit-all

See merge request !71

To bring in the change that should make self-testing this repo
simpler[1]

Link: https://gitlab.com/matthewhughes/gitlab-ci-configurations/-/blob/v0.12.0/CHANGELOG.md [1]

This takes entirely too long to install (I think it downloads _all_ the
dependencies for `renovate`?) just for a hook to validate some config
(this was not a fun experience trying to develop on shitty train
Wifi...)

Print more context so the diff is more helpful than:

    -Count: 1
    +Count: 0

I.e. so I know around which line the change was

Add some more `main` examples so all these behaviours are covered there.

The motivation here is per the added docs: final 'return' statements in
functions that might be difficult to test.

Like the comments commit: move the testing up to `main`. This revealed a
line I don't think we ever expect to reach in practice.

Move testing around

See merge request !72

Mostly to address:

* Drop unhelpfully name `main.go` in the internal lib
* Stop exporting functions that aren't used outside of `internal` (why
  didn't a linter detect these?)

Reorganise code

See merge request !73

fix(deps): update gomod-all

See merge request !64