[MNG-7131] Add regression tests for maven.config one-arg-per-line contract

[gnodet]

Problem

maven.config uses a one-argument-per-line format (introduced by MNG-7131, commit 331c5c3435, July 2021), modelled after Java @argfiles. Each line is a single argv token — whitespace inside a line is never re-split. This allows property values containing spaces:

# .mvn/maven.config
--define
label=Apache Maven

The two lines are passed as two separate tokens to Commons CLI, which consumes the second as the argument to --define.

PR #13093 (2829a73de4) broke this contract by adding flatMap(line -> CleanArgument.splitLine(line).stream()) in MavenParser.parseMavenConfigOptions, re-tokenizing each line on unquoted whitespace. It was reverted in #13148. There were no regression tests protecting this contract, so this PR adds them.

Changes

compat/maven-embedder

• New test fixture: compat/maven-embedder/src/test/projects/mavenConfigSpacedValues/.mvn/maven.config
  Uses the --define / value with spaces two-line form for two properties.
• New test: MavenCliTest#testMavenConfigMultiLineDefineWithSpaces()
  Calls initialize → cli → properties and asserts both user properties are parsed correctly.

impl/maven-cli

• New test class: MavenParserTest (same package as MavenParser for protected access)
  Five test cases covering:
  1. testMultiLineDefineWithSpacedValue — core regression: --define / label=Apache Maven must yield label=Apache Maven (the exact case Fix #13092: tokenize quoted --define in maven.config #13093 broke)
  2. testMultiLineDefineSimple — two-line form without spaces
  3. testSingleLineDefine — compact -Dkey=value form still works
  4. testCommentsAndEmptyLinesSkipped — comment/blank lines are filtered
  5. testGoalRejected — goals throw IllegalArgumentException

Testing

mvn verify -pl compat/maven-embedder -am -B   # MavenCliTest: 1/1 PASS
mvn verify -pl impl/maven-cli -am -B          # MavenParserTest: 5/5 PASS

[gnodet-bot]

Solid regression guard for MNG-7131. The two-layer approach (compat MavenCliTest + impl-level MavenParserTest) is exactly right: the compat test exercises the full initialize → cli → properties pipeline through a real on-disk fixture, while MavenParserTest directly unit-tests parseMavenConfigOptions with all the edge cases that matter.

Specific notes:

• parseMavenConfigOptions is protected in MavenParser, accessible from the same package — the test placement in org.apache.maven.cling.invoker.mvn is correct.
• new MavenParser() instantiates via the default no-arg constructor (no CDI injection required at this level) — valid.
• Five test cases cover: spaced-value two-line form (the regressed case), simple two-line form, compact -D form, comment/blank-line filtering, and goal rejection. Coverage is complete for the documented contract.
• testGoalRejected correctly exercises the IllegalArgumentException path (commandLine.getArgList() returns ["verify"], goals().isPresent() → throws).
• The compat fixture mirrors exactly the format that triggered the MNG-7131 fix: a comment line, two-line --define/label=Apache Maven, two-line --define/revision=1.0.0.
• No functional code is changed — pure test addition.

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