defines, below, describing which other help text TEXT is. The function
should return either TEXT, if it should be used as-is, a replacement
string, which should be malloced, and will be freed by argp, or NULL,
defines, below, describing which other help text TEXT is. The function
should return either TEXT, if it should be used as-is, a replacement
string, which should be malloced, and will be freed by argp, or NULL,