feat(managers/git-submodules): support updating git-tag versions

[Shegox]

This PR introduces support for updating git submodules using versioned git tags. This enhancement is useful for updating submodules to follow specific releases (i.e., tags) rather than tracking a particular branch, such as the main branch of a downstream repository.

Additionally, it changes the versioning scheme from git-refs to semver if the current branch value matches a valid semver format.

Context

Previously, Renovate already supported updating submodules via manual adjustments:

• required to change the versioning to semver
• and the value in the .gitmodules file wasn't updated automatically. (could be overcome with a RegexManager)

fixes #14258
fixes #24827

Inspired by the fork from @pl4nty (#24827 (comment))

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

Demo Repository: https://github.com/Shegox/renovate-submodule-parent
Demo Pull Request: Shegox/renovate-submodule-parent#1

[DanySK]

@Shegox, once merged, how will this work? I am very interested in using it ASAP

Edit: I mean, will this require any additional configuration, or setting a tag name into the branch entry of .gitmodule will suffice?

[Shegox]

Edit: I mean, will this require any additional configuration, or setting a tag name into the branch entry of .gitmodule will suffice?

This should suffice, if your submodule has a standard semver tag versioning and you don't need any other special Renovate magic.
For my use case the full configuration in the renovate.json just enables the git-submodules manager and thats it

{
  "git-submodules": {
    "enabled": true
  }
}

And then my .gitmodules references the tag as branch:

[submodule "deps/renovatebot"]
	path = deps/renovatebot
	url = https://github.com/renovatebot/renovate.git
	branch = 37.425.0

This will then create an update PR like this:

@DanySK You can as well see the demo repository here: https://github.com/Shegox/renovate-submodule-parent (Update PR: Shegox/renovate-submodule-parent#1)

[pl4nty]

@Shegox thanks for this, I'm looking forward to testing it! Would you mind adding Co-authored-by: Tom Plant <tom@tplant.com.au> to 34ca381?

[renovate-release]

🎉 This issue has been resolved in version 38.6.0 🎉

The release is available on:

• GitHub release
• npm package (@latest dist-tag)
• 38.6.0

Your semantic-release bot 📦🚀