https://github.com/rubygems/rubygems/commit/9dbfce76cf

And make sure `bundle install --local` can install from it without git.

https://github.com/rubygems/rubygems/commit/7d6b631620

https://github.com/rubygems/rubygems/commit/0c3a65871a

We don't need an actual checkout since the cache path is no longer used
as the install location. Now the per app cache acts just like the
standard cache.

https://github.com/rubygems/rubygems/commit/686988923c

If we want to change git gems to use a proper cache, instead of using
the cache folder as the install location, so we need to keep git
information in the cache, so that when running `bundle install` or
`bundler install --local`, we are able to figure out whether the
revision that needs to be checked out is present locally in the cache or
needs to be fetched from the remote repository.

https://github.com/rubygems/rubygems/commit/607eda63eb

If Gemfile is empty and there's no lockfile (situation after `bundle init`), and
`frozen` is configured, running `bundle add` will result in an strange
error, like this:

```
$ bundle add rake
, but the lockfile can't be updated because frozen mode is set

You have deleted from the Gemfile:
* rake (~> 13.2)

Run `bundle install` elsewhere and add the updated Gemfile to version control.
```

This commit fixes the problem to instead print

https://github.com/rubygems/rubygems/commit/152331a9dc

https://github.com/rubygems/rubygems/commit/f6f79f4c37

https://github.com/rubygems/rubygems/commit/b373b7ed0d