Expose svu functionality as a library and internal refactoring

[ahaasler]

This PR addresses the need to use svu as a go library directly in code (partially addresses #123) and introduces internal refactoring for maintainability.

I've exposed the public API in pkg/svu, allowing developers to use svu as an import name directly in their code as github.com/caarlos0/svu/pkg/svu.

The exposed API uses a variadic options pattern, which mitigates the risk of future interface breaking changes. This approach ensures easy maintenance through adapter functions and flexibility for internal/svu to implement changes and new features without being restricted with the API contract.

I had to move some functionality from the main package to internal/svu. This does introduce a dependency on internal/git in internal/svu that can be resolved if needed, maybe moving that code to pkg/svu instead?

I've defined constants with command names and tag-mode options to prevent mismatches. However, this change has not been extended to the CLI yet, just in case it's not desired.

Open PR Conflict:

I've noticed an open PR (#125) that conflicts with these changes. I'm open to adapting my code to resolve any conflicts that may arise once that PR is merged. Alternatively, I'm willing to assist in adapting the code in #125 to ensure a smoother merge process if this PR is merged before.

I welcome any input, adjustments, or recommendations from both the community and maintainers to improve this solution and maximize its usefulness for svu users.

[caarlos0]

hey, thanks for the PR @ahaasler

I merged #125 as it seemed easier to integrate that pr here than the other way around.

Other than that, on first look, your PR looks good!
Once we fixed the conflicts I think we can merge it 🙏🏻

[ahaasler]

Hi, I have resolved the conflicts and checked that PR #125 works as expected. During testing I found out that there's a bug in #125 or that the README.md is incorrect:

The docs say:

$ svu current
v1.2.3-alpha.2+123

$ svu prerelease
v1.2.3-alpha.3

$ svu prerelease --pre-release alpha.33 --build 243
v1.2.3-alpha.33+243

But I got different result from both the code in the main branch and with my changes applied:

$ go install github.com/caarlos0/svu@main
go: downloading github.com/caarlos0/svu v1.11.1-0.20230912125155-881d9c3a6e5d
$ svu --version
svu version dev
module version: v1.11.1-0.20230912125155-881d9c3a6e5d, checksum: h1:g7aZc5Zh0HxpTKRVbJvl2o7aFI0ZSt7Gcybw3T4rhRY=

$ git tag
v1.2.3-alpha.2+123
$ git log
commit 579ce447d1589ba0bd37cfaa30ca14f4067a3690 (HEAD -> main, tag: v1.2.3-alpha.2+123)
Author: Adrian Haasler García <dev@ahaasler.com>
Date:   Tue Sep 12 20:54:44 2023 +0200

    feat: add a

$ svu current
v1.2.3-alpha.2+123
$ svu prerelease
v1.2.3-alpha.3
$ svu prerelease --pre-release alpha.33 --build 243
v1.2.3-alpha.34+243

$ ~/workspace/svu/svu current
v1.2.3-alpha.2+123
$ ~/workspace/svu/svu prerelease
v1.2.3-alpha.3
$ ~/workspace/svu/svu prerelease --pre-release alpha.33 --build 243
v1.2.3-alpha.34+243

Notice the v1.2.3-alpha.34+243 instead of v1.2.3-alpha.33+243

[caarlos0]

hmm, looks like a bug indeed

@bradleyjones do you want to take a look?

[bradleyjones]

Fix for that issue here #134

[ahaasler]

Hi, I have resolved the conflicts to include #134.

[caarlos0]

awesome, thank you!