https://github.com/rubygems/rubygems/commit/d478ec403f

Gem::Package::TarReader::Entry now raises EOFError or returns nil
appropriately based on Ruby core IO.read and IO.readpartial behavior.

Zlib will respond accordingly by raising Zlib::GzipFile::Error on EOF.

When verifying a gem or extracting contents, raise FormatError similar
to other cases of corrupt gems.

Addresses a bug where Gem::Package would attempt to call size on nil
instead of raising a more descriptive and useful error, leading users
to assume the problem is internal to rubygems.

Remove unused error class TarReader::UnexpectedEOF that was never raised
since the NoMethodError on nil would happen first. Use EOFError instead.

https://github.com/rubygems/rubygems/commit/dc6129644b

https://github.com/rubygems/rubygems/commit/9d25906e44

https://github.com/rubygems/rubygems/commit/fba6e94de9

TarReader#each previously implemented a partial version of seek.
This code moved to Entry#seek for use from TarReader#each.

Entry#close now returns nil instead of true, like IO#close.

Closing an Entry now seeks to the end of the Entry, seeking past
any remaining zero byte tar file padding and moving the io to the
correcty position to read the next file in the archive.

Uses seek for Entry#rewind and #pos=, fixing the tar->gzip->tar nested
rewind that would break previous to this change.

Add Entry.open that behaves more like File.open.

https://github.com/rubygems/rubygems/commit/f5149565d5

TarReader is used as an IO object, but doesn't behave the same as other
implementations. These fixes make `read` and `readpartial` conform to the
interface of StringIO and File.

https://github.com/rubygems/rubygems/commit/bba32d7217

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

  31a6eaabc165d8a222e176f2c809d90622d88ec2 is obsoleted with
  https://github.com/rubygems/rubygems/pull/3820