https://github.com/rubygems/rubygems/commit/b58829a868

https://github.com/rubygems/rubygems/commit/5956e7f8e5

That restores support for compact index dummy implementations that only lists
versions, without checksums or dependencies.

This format is undocumented, so we may want to get rid of it in the
future. However, some of our tests rely on it, and some implementations
did use it (gems.mutant.dev at least). And the way the code was written
suggest that support was intentional.

So for now, we should restore it.

https://github.com/rubygems/rubygems/commit/0427d8c983

Removes usage of these classes as ACE gadgets

See https://nastystereo.com/security/ruby-3.4-deserialization.html

Signed-off-by: Samuel Giddins <segiddins@segiddins.me>

https://github.com/rubygems/rubygems/commit/89ad04db86

https://github.com/rubygems/rubygems/commit/d8d68cc00e

https://github.com/rubygems/rubygems/commit/0549ddbcc5

In a `bundle exec` context, the local specification will actually be
part of the known specifications, so RubyGems will assume it has already
been installed, which is not actually true.

This will cause `RequestSet` to rebuild extensions for a gem that's not
actually installed, causing errors.

The fix is to make sure detection of installed activation requests
considers not only that there's a known spec with the same full name as
the one being installed, but also that this spec is installed in the
same gem_home were pretend to install the new gem.

https://github.com/rubygems/rubygems/commit/a8ef1286a6

Every time a gem is not found in the Compact Index API, RubyGems will
fallback to the full index, which is very slow. This is unnecessary
because both indexes should be providing the same gems, so if a gem
can't be found in the Compact Index API, it won't be found in the full
index.

We _do_ want a fallback to the full index, whenever the Compact Index
API is not implemented. To detect that, we check that the API responds
to the "/versions" endpoint, just like Bundler does.

Before:

```
$ time gem install fooasdsfafs
ERROR:  Could not find a valid gem 'fooasdsfafs' (>= 0) in any repository
gem  20,77s user 0,59s system 96% cpu 22,017 total
```

After:

```
$ time gem install fooasdsfafs
ERROR:  Could not find a valid gem 'fooasdsfafs' (>= 0) in any repository
gem  5,02s user 0,09s system 91% cpu 5,568 total
```

https://github.com/rubygems/rubygems/commit/c0d6b9eea7

They were delegating their `#hash` value to a class not overriding that
method, and so were returning inconsistent results.

https://github.com/rubygems/rubygems/commit/723e4ee0fc