Function ensure_valid_git_repo 

pub fn ensure_valid_git_repo(path: &Path) -> Result<()>

Ensures a directory contains a valid Git repository or returns a detailed error.

Arguments

• path - The directory path to validate as a Git repository

Return Value

• Ok(()) if the path contains a valid .git directory
• Err(AgpmError::GitRepoInvalid) if the path is not a Git repository