Add documentation for including JRE with Eclipse products

[Copilot]

Users frequently encounter confusion when trying to bundle a JRE with Eclipse products, particularly around the includeJRE="true" flag and its interaction with JustJ and target platform configuration (issues #5579, #4791, #2064).

Changes

• New documentation page: IncludeJRE.md explaining JRE inclusion methods

  • Automatic inclusion via includeJRE="true" (recommended approach)
  • Manual inclusion via explicit JRE features
  • Complete working examples with pom.xml and .product configurations
  • Troubleshooting guide covering common pitfalls
  • FAQ addressing multi-platform builds, JRE variants, and provider alternatives

• Site navigation updates: Added links in site.xml, index.md, and Products.md

Example Configuration

Automatic JRE inclusion with JustJ:

<!-- .product file -->
<product name="My Application" 
         uid="my.application.product"
         includeJRE="true"
         ...>

That's it! No additional pom.xml configuration needed. Tycho automatically fetches the JRE from the JustJ repository via the productRepository parameter (defaults to https://download.eclipse.org/justj/jres).

Optional Customization

If you need to use a specific JRE version:

<plugin>
  <groupId>org.eclipse.tycho</groupId>
  <artifactId>tycho-p2-director-plugin</artifactId>
  <configuration>
    <productRepository>https://download.eclipse.org/justj/jres/21/updates/release/</productRepository>
  </configuration>
</plugin>

Key Points

• Automatic method (includeJRE="true"): Zero configuration needed - Tycho handles JRE fetching automatically
• Manual method (explicit features): Requires JustJ repository in <repositories> and executionEnvironment=none in target-platform-configuration
• The productRepository parameter in tycho-p2-director-plugin controls where Tycho fetches JRE from for automatic inclusion

Screenshot

Documentation page follows existing Tycho site structure and styling, positioned alongside SignProducts documentation under "Building Products" section.

Original prompt

Add a new section to the sitedocs that explains how to inlcude a JRE with the product

We already have SignProducts section that explains the signing, but we also want to have one that explains how to inlcude a JRE in prodcuts as Tycho offers multiple ways.

Esepcially the new option to let tycho include it automatically when the product has the flag includeJRE="true" needs further description as people are often confused how to use it see for further information

• Justj JRE included instead of JRE 21.0.9 when building with Tycho 5 #5579
• Does tycho build ignore justj JRE version request? #4791
• Support automatic installation of a suitable JustJ in a product packaging #2064

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[laeubi]

@copilot please look at my review comments something is out of track here

[Copilot]

@copilot please look at my review comments something is out of track here

Addressed both review comments in commit 5634698:

1. Line 32 - Fixed incorrect Prerequisites section for automatic JRE inclusion. No repository or target platform configuration needed - Tycho automatically fetches JRE via productRepository parameter.

2. Line 118 - Removed incorrect "Customizing the JRE Name" section. The jreName parameter is not meant for customization per the source code documentation.

The documentation now correctly distinguishes between:

• Automatic method: Only needs includeJRE="true", no additional config
• Manual method: Requires JustJ repository and executionEnvironment=none

Screenshot of updated Prerequisites section: https://github.com/user-attachments/assets/c3903f2a-6175-4d32-b4a2-5421fc415d06

[eclipse-tycho-bot]

💚 All backports created successfully

Status	Branch	Result
✅	tycho-5.0.x

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