Fix #13191: add -Dmaven.maven3Personality hint to FATAL message for wrong parent relativePath

[gnodet]

Backport of #13196 to maven-4.0.x.

Summary

Fixes #13191 — improves the FATAL error message when an explicit <relativePath> resolves to a different G:A than the declared parent.

When a POM declares an explicit <relativePath> that resolves to a different G:A than the declared parent, Maven 4 raises a FATAL error. This is correct behaviour — it is a configuration error. However, the error message was unhelpful.

A common cause is maven-shade-plugin generating dependency-reduced-pom.xml with a <relativePath> that is invalid in the generated context (see apache/maven-shade-plugin#813). Users hit a FATAL with no guidance.

Change

Message-only change in mismatchRelativePathAndGA. The FATAL message now mentions:

• that build tools generating POMs with incorrect <relativePath> (e.g. maven-shade-plugin) should be upgraded
• -Dmaven.maven3Personality as an explicit temporary workaround

The right fix

apache/maven-shade-plugin#843: emit <relativePath/> in generated POMs.

[gnodet-bot]

Clean backport of #13196 to maven-4.0.x. Message change is accurate and scoped correctly to the !maven3Mode && !defaultPath branch (explicit <relativePath> pointing at wrong GA). FATAL severity preserved — no behaviour change, only improved diagnostics.

Test testWrongRelativePathInGeneratedPomIsFatalWithMaven3Hint correctly reproduces the shade-plugin scenario: reducedPom has <relativePath>pom.xml</relativePath> resolving to the project's own GA, triggering the FATAL. The three message assertions ("relativePath", "pom.xml", "maven.maven3Personality") all match the actual generated message string. Diff is identical to the master PR.

This review was generated by an AI agent, Hermès on behalf of @gnodet.