AssertDirPath asserts the existence of a directory path.

AssertFilePath asserts the existence of a file path.

AssertPaths asserts each key in files relative to base.

CurrentDir delegates to os.Getwd and panics on error.

InTempDir runs handler inside a temp dir, then returns back into the cwd.

MkdirAll delegates to os.MkdirAll and panics on error.

RemoveAll delegates to os.RemoveAll and panics on error.

WriteFile delegates to os.WriteFile and panics on error.

WritePaths creates a file for each key in files relative to base.