Use DEFAULT_VERSION in get_git_version()

[olantwin]

When creating a conda package for FairLogger (as part of investigating moving SHiP software to conda), I noticed that correct versioning relied on being in a git repository of FairLogger. For conda, it is conventional to build from a source tarball.

This PR upstreams a patch I made for conda that allows setting the version via -DPROJECT_VERSION as default. When in a git repo, PROJECT_VERSION will then be overridden by the information gotten from git. This makes use of the existing DEFAULT_VERSION functionality of get_git_version.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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Configuration used: Organization UI

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Run ID: ad7fc2c0-1fb5-440e-8eb2-e3cea05351ae

📥 Commits

Reviewing files that changed from the base of the PR and between 5aee797 and ba1c329.

📒 Files selected for processing (1)

• CMakeLists.txt

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📝 Walkthrough

Walkthrough

The CMakeLists.txt build configuration now passes DEFAULT_VERSION ${PROJECT_VERSION} to the get_git_version function, ensuring that when Git version information is unavailable, the project falls back to the explicitly defined PROJECT_VERSION instead of an empty value.

Changes

Version initialization

Layer / File(s)	Summary
Git version fallback parameter CMakeLists.txt	get_git_version CMake invocation now supplies DEFAULT_VERSION ${PROJECT_VERSION} to set a fallback value for PROJECT_GIT_VERSION when Git metadata is unavailable.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: passing DEFAULT_VERSION to get_git_version() to enable version configuration via CMake parameters.
Description check	✅ Passed	The description clearly explains the motivation (conda packaging requires non-git builds), the solution (use DEFAULT_VERSION parameter), and how it works with existing git repository detection.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[rbx]

Sounds good, thank you.

Do you need a tag with this?

The base branch was changed.

[olantwin]

No tag needed, I'll drop my patch when the next release is tagged.