Keep only the latest Rails release version information in README

[yahonda]

Summary

Follow-up to #2532. README had accumulated install, upgrade, and troubleshooting blocks for Rails versions that are long out of support, plus stale blog/forum links. This PR keeps only what's relevant to currently supported Rails versions.

Net: README goes from 947 to 603 lines (−344).

What's kept / changed

• INSTALLATION: Rails 8.1 only (readers on older supported Rails are pointed at the matching Git tag for that version's README)
• DESCRIPTION: updated Rails version range to 8.1; Oracle Database version now states "tested with 11g Release 2 (11.2) and higher" rather than claiming 10g support
• Legacy schema support: removed (set_table_name, set_primary_key, set_date_columns etc. were dropped by modern ActiveRecord)
• UPGRADE section: removed (all entries covered upgrading to Rails 5.x)
• Phusion Passenger troubleshooting: removed dead 2008 blog links; kept the required environment variables (LD_LIBRARY_PATH / TNS_ADMIN / NLS_LANG / ORACLE_HOME) under a more general heading
• LINKS: removed abandoned rayapps blog and Google groups links; upgraded remaining http://github.com URLs to https://
• Remote tables over database links: rewrote the one-liner example. self.table_name = "hr_employees@db_link" does not work — quote_table_name strips the @db_link suffix and some code paths raise ArgumentError: db link is not supported. Recommend Rails multiple-database support when the app can connect to the remote database directly, and document a validated synonym-based workaround for when only a database link is available.

Database-link validation

Tested end-to-end against FREEPDB1 with ruby-oci8 on adapter afb820a5 (master):

• self.table_name = "employees_remote_only@loop_lnk" — count generated SELECT COUNT(*) FROM "EMPLOYEES_REMOTE_ONLY" (dblink silently stripped), and .first raised ArgumentError: db link is not supported from extract_schema_qualified_name.
• CREATE SYNONYM employees_via_link FOR employees_remote_only@loop_lnk; + self.table_name = "employees_via_link" — returned the correct remote rows (columns_hash, count, order.pluck all worked). The generated SQL never contains @, so the adapter's dblink-rejection logic is never triggered and Oracle transparently follows the synonym through the link.

Test plan

• Markdown renders on GitHub without broken anchors
• No remaining git:// URLs
• No remaining http://github.com/rsim/... URLs (all upgraded to https://)
• Database-link guidance validated end-to-end (see above)

🤖 Generated with Claude Code

[yahonda]

A couple of notes on this PR:

• Review order: this PR depends on the same README area as Replace RUNNING_TESTS.md with CONTRIBUTING.md #2532 (both touch the "RUNNING TESTS / CONTRIBUTING" link at the bottom). Please review and merge Replace RUNNING_TESTS.md with CONTRIBUTING.md #2532 first; I'll rebase this branch on top afterwards so the diff stays clean.

• Backwards compatibility: removing the older Rails install/upgrade/schema sections does not leave users stranded. Anyone on an older Rails can read the historical documentation from the corresponding release branch or Git tag on GitHub — e.g. git show v7.0.0:README.md or the tags page. The README on master should reflect what master supports; historical snapshots already live in the tag/branch history.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Updates README to focus on currently supported Rails versions by removing outdated installation/upgrade/troubleshooting content and refreshing links.

Changes:

• Narrows installation guidance to Rails 8.1 and removes legacy Rails/version blocks
• Removes legacy schema and Rails 5.x upgrade notes
• Cleans up troubleshooting section and modernizes GitHub links to HTTPS

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[Copilot]

This Ruby example uses self.table_name \"...\", which calls a table_name method rather than the ActiveRecord table_name= setter. Update the example to use the setter so it matches how ActiveRecord expects table names to be configured.

Suggested change

	self.table_name "hr_employees@db_link"
	self.table_name = "hr_employees@db_link"

[yahonda]

Fixed — changed to self.table_name = "hr_employees@db_link".

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 3 comments.

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[Copilot]

This Rails 2-specific note conflicts with the PR’s stated goal of keeping the README relevant to currently supported Rails versions (8.1). Consider removing it or rephrasing it in a version-neutral way (e.g., focusing on modern Rails only), since Rails 2 is long out of support.

Suggested change

	In case of Rails 2 application you do not need to use `ActiveSupport.on_load(:active_record) do ... end` around settings code block.
	For Rails 8.1 applications, wrap adapter settings in `ActiveSupport.on_load(:active_record) do ... end` as shown above.

[Copilot]

The PR description says 'Legacy schema support' was removed, but the '### Legacy schema support' heading remains. If the section content was removed, also remove this heading; if some content is still intended to remain, rename the heading to match what follows so the TOC/anchors aren’t misleading.

[Copilot]

“This branch supports …” can be ambiguous when the README is consumed outside Git context (e.g., as rendered on RubyGems). Consider wording that’s unambiguous in all contexts (e.g., “The 8.1.x adapter series supports Rails 8.1 …”).

Suggested change

	Oracle enhanced ActiveRecord adapter provides Oracle database access from Ruby on Rails applications. This branch supports Ruby on Rails 8.1 and is tested with Oracle Database 11g Release 2 (11.2) and higher. For earlier Rails versions, see the corresponding release branch or Git tag.
	Oracle enhanced ActiveRecord adapter provides Oracle database access from Ruby on Rails applications. The 8.1.x adapter series supports Ruby on Rails 8.1 and is tested with Oracle Database 11g Release 2 (11.2) and higher. For earlier Rails versions, see the corresponding release branch or Git tag.