fix: handle stat errors in file helpers

[immanuwell]

Description
IsFile and IsDir assumed os.Stat always returns FileInfo unless the path is missing. But file/child, where file is a regular file, returns a stat error and nil info, so the old code panics.

This returns false on any stat error, same vibe as "not a file/dir". tiny fix, low-key useful.

Repro:

1. create a regular file
2. call IsFile("<tmp>/file/child") or IsDir("<tmp>/file/child")
3. before: nil pointer panic in IsFile/IsDir
4. after: returns false

User facing changes
No CLI output changes, just avoids a crash for bad local paths.

Testing

• go test ./pkg/skaffold/util -run 'TestIsFileIsDir|TestIsFileIsDirStatError'\n- go test ./pkg/skaffold/util\n- make quicktest

[gemini-code-assist]

Code Review

This pull request refactors the IsFile and IsDir utility functions to simplify error handling, ensuring they return false on any os.Stat error. A new test case is also included to verify this behavior. The reviewer recommends adding documentation comments to these exported functions to align with Go best practices.

[gemini-code-assist]

Exported functions should have a documentation comment according to Go best practices. This provides clarity on the function's behavior, such as whether it follows symlinks and how it handles errors.

Suggested change

	func IsFile(path string) bool {
	// IsFile returns true if the path exists and is a regular file. Symlinks are followed.
	func IsFile(path string) bool {

References

1. All exported names should have a doc comment. This is a standard practice in Go to improve code maintainability and discoverability. ^(link)

[gemini-code-assist]

Exported functions should have a documentation comment according to Go best practices. This clarifies that the function follows symlinks and returns false on any error.

Suggested change

	func IsDir(path string) bool {
	// IsDir returns true if the path exists and is a directory. Symlinks are followed.
	func IsDir(path string) bool {

References

1. All exported names should have a doc comment. This is a standard practice in Go to improve code maintainability and discoverability. ^(link)