https://github.com/ruby/rubygems/commit/d3baf4110e

This has the following benefits:

* Avoid duplicated work in some specs that first build a repo, and then
  overwrite it with a completely different set of gems.
* Reduce RSpec nesting and improve readability.
* The change also made surfaces several specs that were incorrect since
  they were unintentionally not testing the right thing.

https://github.com/rubygems/rubygems/commit/ed430883e0

As long as some spec in the materialization is complete.

https://github.com/rubygems/rubygems/commit/9a673b0bbb

For consistency with other specs.

https://github.com/rubygems/rubygems/commit/a5b2449896

https://github.com/rubygems/rubygems/commit/c519830d4d

Even if all gems are properly installed and no resolve is needed, we
recently started always reading all packages in `vendor/cache` and
extracting specifications from them.

This commit fixes the problem by longer making considering cached specs
the default and only enable them when a resolve is actually needed.

https://github.com/rubygems/rubygems/commit/edeb2c42bf

https://github.com/rubygems/rubygems/commit/146de56353

https://github.com/rubygems/rubygems/commit/bb66253f2c

Looks for the CHECKSUMS section in the lockfile, activating the feature
only if the section exists. Without a CHECKSUMS section, Bundler will
continue as normal, validating checksums when gems are installed while
checksums from the compact index are present.

https://github.com/rubygems/rubygems/commit/2353cc93a4