Allow specific message bundle config ignore for post-install messages

Describe the problem as clearly as you can

bundle config set ignore_messages.<gem> true suppresses all post-install messages from that gem, forever. There's no way to silence one specific message while still seeing a different message the same gem prints later (e.g. a new deprecation notice, or a security warning).

In practice this means teams either live with a message they've already read on every bundle install, or they opt out of that gem's post-install channel entirely and risk missing something that actually matters in the future.

Common real-world examples: readline and httparty both print a post-install message that has stayed identical across many releases. Once you've read it, there's no benefit to seeing it again on every install — but fully ignoring the gem means a genuinely new message (a security notice, a breaking change) would go unseen too.

Did you try upgrading rubygems & bundler?

Yes — reproduced on the latest release.

Post steps to reproduce the problem

1. Add a gem with a post_install_message to your Gemfile (e.g. httparty).
2. Run bundle install. Note the message prints every time.
3. Run bundle config set ignore_messages.httparty true.
4. Run bundle install again — the message is gone, but so would any future, different message from that gem.

Which command did you run?

bundle install / bundle config set ignore_messages.<gem> true

What were you expecting to happen?

A way to suppress a specific message (e.g. by exact text or a digest of it) so that only that message is silenced — if the gem later changes or adds a different post-install message, it should still show up.

What happened instead?

ignore_messages only accepts a gem name and suppresses every message from that gem indiscriminately, with no content-level granularity.

Proposed API, for discussion:

bundle config set ignore_messages.httparty.<message-digest> true

A digest (e.g. SHA of the message text) matches on the message itself, so it keeps working even if a gem changes its message without bumping the version, and doesn't require Bundler to reason about version ordering.

We considered scoping suppression to the gem version instead (ignore_messages.httparty.<version> true), but ruled it out: gems like readline and httparty keep the same message across many releases, so per-version scoping would force you to re-suppress on every upgrade even though nothing changed — the opposite of "set it once and only hear about it when it's actually new."

Environment

Bundler       4.0.19
  Platforms   ruby, arm64-darwin-23
Ruby          <any>
RubyGems      4.0.19

Start by tracing bundle config set ignore_messages.<gem> true and bundle install, focusing on how post-install messages are selected and suppressed. Define how a message digest is stored and matched, then verify that an unchanged message is hidden while a changed or additional message still appears.