Adds name with permissions mode to the tar, yielding io for writing the file. The digest_algorithm is written to a read-only name.sum file following the given file contents containing the digest name and hexdigest separated by a tab.
The created digest object is returned.
Pins the gem name to the given source. Adding a gem with the same name from a different source will raise an exception.
Checks if there are duplicate links with the same type and hreflang attributes that have an alternate (or empty) rel attribute
Raises a TooMuchTagError if there are duplicates found