fix(git): check destination emptiness without full readdir

[AdeshDeshmukh]

Avoid reading an entire directory just to determine if clone destination is empty. Use ReadDir(1) to detect emptiness efficiently while preserving error behavior for non-empty and inaccessible paths.

Description

This PR improves clone destination validation in pkg/lib/external/git/clone.go.

Previously, checkDestination used os.ReadDir(path) to determine whether a directory is empty, which reads the entire directory contents even though only an empty/non-empty check is needed.

This change replaces that with a one-entry probe:

• os.Open(path)
• ReadDir(1)

Behavior is preserved:

• err == nil => directory is non-empty
• err == io.EOF => directory is empty
• other errors => return wrapped inspection error

Validation:

• go test ./pkg/lib/external/git (pass)

Linked issues

N/A

[gorkem]

Can you add the sign-off messages to your commits. Click on the failing DCO check above for how to instructions.

[Copilot]

Pull request overview

Improves clone destination validation in the Git external helper by checking whether the destination directory is empty without reading the entire directory listing, reducing unnecessary I/O for large directories.

Changes:

• Replace os.ReadDir(path) full directory reads with os.Open(path) + ReadDir(1) to detect emptiness.
• Add io import to handle io.EOF from the one-entry probe and preserve existing error semantics.

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[gorkem]

@AdeshDeshmukh please fix failing DCO check before we can review this.