Function splitCpArg

cli/command/container/cp.go:502–516

We use `:` as a delimiter between CONTAINER and PATH, but `:` could also be in a valid LOCALPATH, like `file:name.txt`. We can resolve this ambiguity by requiring a LOCALPATH with a `:` to be made explicit with a relative or absolute path: `/path/to/file:name.txt` or `./file:name.txt` This is app

(arg string)

// client, a `:` could be part of an absolute Windows path, in which case it
// is immediately proceeded by a backslash.
func splitCpArg(arg string) (ctr, path string) {
	if isAbs(arg) {
		// Explicit local absolute path, e.g., `C:\foo` or `/foo`.
		return "", arg
	}

	ctr, path, ok := strings.Cut(arg, ":")
	if !ok || strings.HasPrefix(ctr, ".") {
		// Either there's no `:` in the arg
		// OR it's an explicit local relative path like `./file:name.txt`.
		return "", arg
	}

	return ctr, path
}

// IsAbs is a platform-agnostic wrapper for filepath.IsAbs.
//