Cut CI time in the plugin repositories #12

The CI of the repositories that use apache/maven-gh-actions-shared/.github/workflows/maven-verify.yml costs more than it needs to, in two ways.

The matrix

Across the last 148 CI runs of these repositories (6,107 job-minutes), Windows took 42% of the job-minutes and macOS 25%. A run has up to 16 jobs: JDK 8, 21 and 25 with Maven 3, plus JDK 21 and 25 with Maven 4, on each OS, plus the fail-fast job. In bursts of Dependabot PRs, one job in ten waited 8 to 13 minutes for a runner, macOS the longest.

Each repository now excludes, through matrix-exclude:

• on macOS, every JDK but the newest one in its matrix;
• on Windows, every JDK but the oldest and the newest.

Linux keeps the full matrix. With the default JDK matrix that is 11 jobs instead of 16, 2 of them on macOS instead of 5, and about a third fewer job-minutes, going by the measured share of each OS and JDK. An OS-specific bug that shows up only on a middle JDK is the coverage given up.

The integration tests

Each IT is a Maven run of a few seconds, and mojo-parent sets no invoker.parallelThreads, so the ITs ran one at a time and were bound by JVM startup. Repositories with enough ITs to matter now set invoker.parallelThreads to 0.75C and start the IT JVMs with -XX:TieredStopAtLevel=1 -XX:+UseSerialGC through JAVA_TOOL_OPTIONS. These flags stay out of mojo-parent: every JVM that reads JAVA_TOOL_OPTIONS prints a Picked up line, which can break ITs that compare output, so each repository's own CI has to show it is safe.

The first three:

Two repositories forced one IT thread on Windows. The exec-maven-plugin profile cites MRESOLVER-372, fixed in Resolver 1.9.17 (Maven 3.9.5); CI runs Maven 3.10.0 and 4.0.0-rc-7.

Pull requests

The ITs, merged: mojohaus/versions#1411, mojohaus/license-maven-plugin#753, mojohaus/flatten-maven-plugin#538.

This sweep:

• Run fewer JDKs on macOS and Windows and the ITs in parallel animal-sniffer#355: Run fewer JDKs on macOS and Windows and the ITs in parallel
• Run the ITs in parallel with C1 only and the serial GC aspectj-maven-plugin#274: Run the ITs in parallel with C1 only and the serial GC (stacked on Fix the flaky classpath IT and the site build aspectj-maven-plugin#275, which fixes a flaky IT and the site build)
• Run fewer JDKs on macOS and Windows and the ITs in parallel build-helper-maven-plugin#252: Run fewer JDKs on macOS and Windows and the ITs in parallel
• Run fewer JDKs on macOS and Windows buildnumber-maven-plugin#289: Run fewer JDKs on macOS and Windows
• Run fewer JDKs on macOS and Windows and the ITs in parallel exec-maven-plugin#545: Run fewer JDKs on macOS and Windows and the ITs in parallel (JVM options through MAVEN_OPTS: its ITs compare what forked JVMs print)
• Run fewer JDKs on macOS and Windows and the ITs in parallel extra-enforcer-rules#371: Run fewer JDKs on macOS and Windows and the ITs in parallel
• Run fewer JDKs on macOS and Windows flatten-maven-plugin#540: Run fewer JDKs on macOS and Windows
• Run fewer JDKs on macOS and Windows and the ITs in parallel javacc-maven-plugin#119: Run fewer JDKs on macOS and Windows and the ITs in parallel
• Run fewer JDKs on macOS and Windows and the ITs in parallel jaxb2-maven-plugin#437: Run fewer JDKs on macOS and Windows and the ITs in parallel
• Run fewer JDKs on macOS and Windows jdepend-maven-plugin#99: Run fewer JDKs on macOS and Windows
• Run fewer JDKs on macOS and Windows keytool#153: Run fewer JDKs on macOS and Windows
• Run fewer JDKs on macOS and Windows l10n-maven-plugin#62: Run fewer JDKs on macOS and Windows
• Run fewer JDKs on macOS and Windows license-maven-plugin#754: Run fewer JDKs on macOS and Windows
• Run fewer JDKs on macOS and Windows mrm#323: Run fewer JDKs on macOS and Windows
• Run fewer JDKs on macOS and Windows properties-maven-plugin#170: Run fewer JDKs on macOS and Windows
• Run fewer JDKs on macOS and Windows taglist-maven-plugin#203: Run fewer JDKs on macOS and Windows
• Run fewer JDKs on macOS and Windows tidy-maven-plugin#139: Run fewer JDKs on macOS and Windows
• Run fewer JDKs on macOS and Windows versions#1412: Run fewer JDKs on macOS and Windows
• Run fewer JDKs on macOS and Windows wagon-maven-plugin#181: Run fewer JDKs on macOS and Windows
• Run fewer JDKs on macOS and Windows xml-maven-plugin#187: Run fewer JDKs on macOS and Windows

Not changed: templating-maven-plugin tests one JDK, rpm-maven-plugin runs on Linux only, and maven-native, buildplan-maven-plugin, native2ascii-maven-plugin, servicedocgen-maven-plugin and mojo-parent do not use the shared workflow.

Dependabot

Dependabot PRs were 124 of the 366 CI runs between 2026-09-10 and 2026-10-10. Each repository now checks monthly instead of daily; Maven minor and patch updates come as one PR, GitHub Actions updates as another, and Maven major updates one PR each. Security updates are not affected.

• Check dependencies monthly and group the updates animal-sniffer#356
• Check dependencies monthly and group the updates aspectj-maven-plugin#276
• Check dependencies monthly and group the updates build-helper-maven-plugin#253
• Check dependencies monthly and group the updates buildnumber-maven-plugin#290
• Check dependencies monthly and group the updates buildplan-maven-plugin#307
• Check dependencies monthly and group the updates exec-maven-plugin#546
• Check dependencies monthly and group the updates extra-enforcer-rules#373
• Check dependencies monthly and group the updates flatten-maven-plugin#541
• Check dependencies monthly and group the updates javacc-maven-plugin#120
• Check dependencies monthly and group the updates jaxb2-maven-plugin#438
• Check dependencies monthly and group the updates jdepend-maven-plugin#100
• Check dependencies monthly and group the updates keytool#154
• Check dependencies monthly and group the updates l10n-maven-plugin#63
• Check dependencies monthly and group the updates license-maven-plugin#755
• Check dependencies monthly and group the updates maven-native#190
• Check dependencies monthly and group the updates mojo-parent#788
• Check dependencies monthly and group the updates mojohaus.github.io#108
• Check dependencies monthly and group the updates mrm#324
• Check dependencies monthly and group the updates native2ascii-maven-plugin#98
• Check dependencies monthly and group the updates properties-maven-plugin#171
• Check dependencies monthly and group the updates taglist-maven-plugin#204
• Check dependencies monthly and group the updates templating-maven-plugin#127
• Check dependencies monthly and group the updates tidy-maven-plugin#140
• Check dependencies monthly and group the updates versions#1413
• Check dependencies monthly and group the updates wagon-maven-plugin#182
• Check dependencies monthly and group the updates xml-maven-plugin#188