Print a link to the release notes instead of the whole changelog on `gem update --system`

[kenchan]

Describe the problem as clearly as you can

gem update --system prints every CHANGELOG.md entry newer than the version you're upgrading from. On the official ruby:3.4 Docker image, that's 478 of the 499 lines it prints; on ruby:3.3, 716 of 737. It comes from show_release_notes in lib/rubygems/commands/setup_command.rb, which is called unconditionally.

CHANGELOG.md is now over 7,000 lines and generated from merged PR titles (tool/changelog.rb), so what gets printed is closer to a list of PR titles than to release notes:

* Check the resolved parent directory before extracting old format gems. Pull request [#9755](https://github.com/ruby/rubygems/pull/9755) by hsbt
* Installs bundler 4.0.18 as a default gem.

Neither existing flag covers this. --quiet isn't forwarded to setup.rb — duckinator mentioned in #4355 that they hadn't touched it ("I didn't know it existed"). --silent does silence the changelog, but it silences errors too (gem install --silent no-such-gem prints nothing and exits 2), which seems fair enough for --silent. In #3789, duckinator said they "would like something between the changelog-dump and silence, too".

Which raises the question: should gem update --system print the changelog at all, or would a link to the release notes be enough?

Did you try upgrading RubyGems?

Yes — and upgrading can't fix this one by itself. As duckinator pointed out in #4355, a flag-based fix "will only help when updating from versions with the fix", and the changelog is printed by the child process — system(*Shellwords.split(Gem.ruby), "--disable-gems", "setup.rb", *args). Only a change to the child's default reaches people upgrading from an older RubyGems.

Post steps to reproduce the problem

See below.

Which command did you run?

$ docker run --rm ruby:3.4 sh -c 'gem update --system | wc -l'
499

$ docker run --rm ruby:3.3 sh -c 'gem update --system | wc -l'
737

What were you expecting to happen?

A summary of what was installed: the versions, the executables, and where to read about the changes.

Concretely, I'd expect something like this to be enough:

  def show_release_notes
    say "See https://github.com/ruby/rubygems/releases for the release notes."
  end

The CHANGELOG.md parsing would go away too. setup.rb would keep accepting --previous-version, since older parents still pass it; only its last use (setup_command.rb:573) would be removed.

Measured on the ruby:3.4 Docker image, with rubygems-update already installed, so the same command runs in both cases (which is why it's 498 rather than the 499 above — the Successfully installed rubygems-update line isn't printed):

gem update --system	stdout
today	498 lines
with the above	20 lines

I picked /releases because it lists releases newest-first, so the version you just installed is at the top, but the gemspec's changelog_uri (blob/master/CHANGELOG.md) would work just as well.

What actually happened?

478 of the 499 lines were the changelog:

Installing RubyGems 4.0.19
  Successfully built RubyGem
  Name: bundler
  Version: 4.0.19
  File: bundler-4.0.19.gem
Bundler 4.0.19 installed
RubyGems 4.0.19 installed
Regenerating binstubs
Regenerating plugins

## 4.0.19 / 2026-08-20

[... 478 lines, 23 release headings ...]

* Fix heading ranks in documentation. Pull request
  [#8711](https://github.com/ruby/rubygems/pull/8711) by antoinem


------------------------------------------------------------------------------

RubyGems installed the following executables:
	/usr/local/bin/gem
	/usr/local/bin/bundle
	/usr/local/bin/bundler

RubyGems system software updated

Run gem env and paste the output below

RubyGems Environment:
  - RUBYGEMS VERSION: 3.6.9
  - RUBY VERSION: 3.4.10 (2026-06-30 patchlevel 104) [x86_64-linux]
  - INSTALLATION DIRECTORY: /usr/local/bundle
  - USER INSTALLATION DIRECTORY: /root/.local/share/gem/ruby/3.4.0
  - RUBY EXECUTABLE: /usr/local/bin/ruby
  - GIT EXECUTABLE: /usr/bin/git
  - EXECUTABLE DIRECTORY: /usr/local/bundle/bin
  - SPEC CACHE DIRECTORY: /root/.cache/gem/specs
  - SYSTEM CONFIGURATION DIRECTORY: /usr/local/etc
  - RUBYGEMS PLATFORMS:
     - ruby
     - x86_64-linux
  - GEM PATHS:
     - /usr/local/bundle
     - /root/.local/share/gem/ruby/3.4.0
     - /usr/local/lib/ruby/gems/3.4.0
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :backtrace => true
     - :bulk_threshold => 1000
     - "gem" => "--no-document"
  - REMOTE SOURCES:
     - https://rubygems.org/

Past changes here (#3041, #4145, #4198) tuned how much gets printed, so this is a different kind of change. How does that sound?

[hsbt]

I accidentally closed this 🙏