Make check_existing function return whether a path exists

[James Frost (jfrost-mo)]

PR Summary

Make check_existing function return whether a path exists. This avoids the need to separately check this in other code.

This is a refactoring PR ahead of some modifications to the cloning function; I have split it into a separate PR for ease of review as it touches a couple places that are otherwise unaffected.

Sci/Tech Reviewer:
Code Reviewer:

Code Quality Checklist

• I have performed a self-review of my own code
• My code follows the project's style guidelines
• Comments have been included that aid understanding and enhance the readability of the code (Docstring updated.)
• My changes generate no new warnings
• All automated checks in the CI pipeline have completed successfully

Testing

• This change has been tested appropriately (please describe)

I have run an existing workflow (u-dn674) with this change and observed no change in behaviour.

Security Considerations

• I have reviewed my changes for potential security issues

No change in security properties. The same check happens, just within the function rather than outside it. This makes it harder to forget.

• Sensitive data is properly handled (if applicable)
• Authentication and authorisation are properly implemented (if applicable)

AI Assistance and Attribution

• Some of the content of this change has been produced with the assistance of Generative AI tool name (e.g., Met Office Github Copilot Enterprise, Github Copilot Personal, ChatGPT GPT-4, etc) and I have followed the Simulation Systems AI policy (including attribution labels)

Sci/Tech Review

• I understand this area of code and the changes being added
• The proposed changes correspond to the pull request description
• Documentation is sufficient (do documentation papers need updating)
• Sufficient testing has been completed

(Please alert the code reviewer via a tag when you have approved the SR)

Code Review

• All dependencies have been resolved
• Related Issues have been properly linked and addressed
• Code quality standards have been met
• Tests are adequate and have passed
• Security considerations have been addressed
• Performance impact is acceptable

[github-actions]

Hello James Frost (@jfrost-mo)! 👋

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[James Frost (jfrost-mo)]

Ack, stacked PRs don't work across forks! I'll open this as one PR then.