fix(utils): Make execa usage consistent in git utils

[zpao]

This brings the usage in line with the rest of the calls to git.

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[Copilot]

Pull request overview

This PR updates getFileCommitDate() in Docusaurus’ git utilities to invoke git log via execa('git', [...args]) instead of building a single shell command string, aiming to align the calling style with other git invocations in the module.

Changes:

• Replaces a string-based git command with an argv-based execa('git', args, options) call for git log.
• Refactors conditional args for the “oldest” case into an array spread (--follow, --diff-filter=A).

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[Dharya-dev]

This is a great cleanup! Moving away from shell: true and raw string concatenation for the git command arguments is much safer and avoids potential shell injection or escaping issues with paths containing special characters.

Using the array format for execa is definitely the best practice here. The code looks cleaner and more robust now. Thanks for standardizing this!

[slorber]

LGTM, but I'll do a few more tests before merging later this week, because with our new VCS system I don't think our e2e tests cover this code path anymore.