(https://github.com/ruby/rubygems/pull/8183)

* Add new gem templates

* Add `--ext=go` in `bundle gem`

* Add setup-go to .github/workflows/main.yml

* Embed go version in go.mod

* Use go in bundler CI

* Add example method to template

* Install Go in .circleci/config.yml

* Install Go in .gitlab-ci.yml

* Allow hard tabs in go template

* Run `rake update_manifest`

* Fix test

* Move go_gem to gemspec

Respect to 9b0ec80

* nits: :golf:

* includes valid module name in go.mod

* generate header file

* Run `go mod tidy` to create `go.sum`

* Check if `go.sum` is generated only when Go is installed

To avoid test failure in environments where Go is not installed

* Run CI

* Workaround for hung up

c.f. https://github.com/rubygems/rubygems/actions/runs/11639408044/job/32415545422

* Write man for --ext=go

* Re-generate man with `./bin/rake man:build`

* pinning :pushpin:

* Update with `./bin/rake man:build`

* nits: Extract to method

* nits: Use `sys_exec` instead of `system`

* Clean go module cache after test

Workaround following error

```
1) bundle gem gem naming with underscore --ext parameter set with go includes go_gem extension in extconf.rb
   Failure/Error: FileUtils.rm_r(dir)

   Errno::EACCES:
     Permission denied @ apply2files - /home/runner/work/rubygems/rubygems/bundler/tmp/2.2/home/go/pkg/mod/gopkg.in/yaml.v3@v3.0.1/decode_test.go
   # ./spec/support/helpers.rb:37:in `block in reset!'
   # ./spec/support/helpers.rb:21:in `each'
   # ./spec/support/helpers.rb:21:in `reset!'
   # ./spec/spec_helper.rb:130:in `block (2 levels) in <top (required)>'
   # /home/runner/work/rubygems/rubygems/lib/rubygems.rb:303:in `load'
   # /home/runner/work/rubygems/rubygems/lib/rubygems.rb:303:in `activate_and_load_bin_path'
```

Files installed with `go get` have permissions set to 444
ref. https://github.com/golang/go/issues/35615

```
$ ls -l /home/runner/work/rubygems/rubygems/bundler/tmp/2.2/home/go/pkg/mod/gopkg.in/yaml.v3@v3.0.1/decode_test.go
-r--r--r-- 1 runner runner 42320 Nov 15 06:38 /home/runner/work/rubygems/rubygems/bundler/tmp/2.2/home/go/pkg/mod/gopkg.in/yaml.v3@v3.0.1/decode_test.go
```

So they cannot be deleted by `FileUtils.rm_r`.
Therefore, this is necessary to execute `go clean -modcache` separately from `FileUtils.rm_r` to circumvent it.

* Remove needless changes

ref. https://github.com/ruby/rubygems/pull/8183#discussion_r2532902051

* ci: setup-go is needless

* Don't run go command in `bundle gem`

ref. https://github.com/ruby/rubygems/pull/8183#discussion_r2532765470

* Revert unrelated date changes

---------

https://github.com/ruby/rubygems/commit/260d7d60b3

Co-authored-by: Hiroshi SHIBATA <hsbt@ruby-lang.org>

If the CLI flags are used, we abort early as usual.

As per the settings, I decided to ignore them. We've been migrating them
automatically to the new name for a long time and we don't yet have a
standard way to deprecate and remove settings (we should probably use
the existing setting validators). So I think it's fine for now to do
what we normally do (ignore the setting).

https://github.com/rubygems/rubygems/commit/8311de6e69

https://github.com/rubygems/rubygems/commit/573ffad3ea

For synopsis, subcommand and flag documentation like other commands do.

https://github.com/rubygems/rubygems/commit/f528029756

There already different ways of toggling off this behavior, like setting
`bundle config clean false`, or configuring Bundler to install to system
gems with `bundle config path.system true`.

https://github.com/rubygems/rubygems/commit/6daa09f60a

https://github.com/rubygems/rubygems/commit/f2826dafce

https://github.com/rubygems/rubygems/commit/9f1d07685f

https://github.com/rubygems/rubygems/commit/19739ba71c