[MASSEMBLY-947] Normalize CR line endings to CRLF

[wilx]

Fixes #1154.

Summary

Normalize old Mac CR-only line endings to CRLF when an assembly file set uses
<lineEnding>crlf</lineEnding> (or its windows/dos aliases).

WindowsLineFeedInputStream now treats CR, LF, and CRLF as logical line
separators and emits exactly one CRLF for each. A one-byte lookahead preserves
the byte following a lone CR, while the existing option to add a final line
ending at EOF continues to work without adding a duplicate CRLF.

Root cause

The previous stream converted a bare LF to CRLF and recognized an existing
CRLF, but passed a CR not followed by LF through unchanged. As a result,
filtering the CR-only source from the issue reproducer still left CR-only line
endings in the assembled file despite the requested crlf setting.

Unit tests cover lone and trailing CRs, consecutive CRs, and mixed CR/LF/CRLF
input. The existing Windows-line-ending Invoker project now also generates a
CR-only resource during setup, avoiding source-control newline conversion, and
verifies the assembled bytes exactly.

Compatibility and verification

• Maven 3.6.3 with Java 8:
  mvn -DminimalMavenBuildVersion=3.6.3 -Prun-its clean verify passed with
  271 unit tests and all 150 Invoker builds.
• Maven 3.9.16 with Java 21:
  mvn -Prun-its clean verify passed with 271 unit tests and all 150 Invoker
  builds.
• Maven 4.0.0-rc-5 with Java 21: all 271 unit tests passed, and the focused
  Invoker run containing this regression passed. The full Invoker run passed
  145 of 150 projects; the remaining five are unrelated parent-cycle fixtures
  also failing on master.

Before the implementation change, the new focused unit coverage failed for
all four CR-only/mixed-ending cases.

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[Copilot]

Pull request overview

This PR fixes MASSEMBLY-947 by ensuring that when a file set requests CRLF (<lineEnding>crlf</lineEnding> and aliases), inputs using old Mac CR-only line endings are normalized to CRLF during assembly filtering, rather than leaving bare \r unchanged.

Changes:

• Update WindowsLineFeedInputStream to treat CR, LF, and CRLF as line separators and emit exactly one CRLF per logical line ending (using a one-byte lookahead for lone CR).
• Expand unit coverage to include CR-only, trailing CR, consecutive CRs, and mixed CR/LF/CRLF cases.
• Strengthen the existing Invoker IT by generating a CR-only input during setup and asserting exact assembled output for both the existing and new fixture files.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/main/java/org/apache/maven/plugins/assembly/utils/WindowsLineFeedInputStream.java	Normalizes CR-only and mixed line separators to CRLF using lookahead and pending-byte buffering.
src/test/java/org/apache/maven/plugins/assembly/utils/WindowsLineFeedInputStreamTest.java	Adds targeted tests covering CR-only and mixed-ending normalization behavior.
src/it/projects/file-sets/multimodule-win-lineEndings/setup.groovy	Creates a CR-only resource at test runtime to avoid SCM newline conversion and reproduce the bug reliably.
src/it/projects/file-sets/multimodule-win-lineEndings/verify.groovy	Verifies the assembled output content exactly (including line-ending bytes) for both fixtures.
src/it/projects/file-sets/multimodule-win-lineEndings/child/pom.xml	Pins the parent relativePath to the shared IT parent POM for stable resolution in the IT layout.

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