Simplify complex expressions

Break down complex code structures into simpler, more readable forms. This includes avoiding deep nesting, extracting complex logic into helper functions, simplifying boolean expressions, and reducing code duplication.

Key practices:

• Use match statements instead of multiple if conditions for the same variable
• Extract repeated logic into helper functions rather than duplicating code
• Hoist complex expressions out of tuple/struct construction into separate variables
• Simplify boolean expressions (e.g., use !(a || b) instead of separate conditions)
• Avoid deep nesting by using early returns or extracting functions
• Use functional patterns like unwrap_or() instead of imperative if/else blocks
• Wrap repetitive code patterns in helper functions

Example of improvement:

// Before: Complex nested conditions
if filename == "package.json" {
    // logic
}
if filename == "package.json" || filename == "pom.xml" {
    // more logic
}

// After: Clear match statement
match (generate_opts.author_url, filename) {
    (Some(url), "package.json" | "pom.xml") => replacement.replace(AUTHOR_URL_PLACEHOLDER, url),
    (None, "package.json") => replacement.replace(AUTHOR_URL_PLACEHOLDER_JS, ""),
    (None, "pom.xml") => replacement.replace(AUTHOR_URL_PLACEHOLDER_JAVA, ""),
    _ => {},
}

This approach improves code maintainability, reduces cognitive load, and makes the codebase more approachable for new contributors.