Add configurable skipMergeCommits parameter to Git info command

[GabriRuflex]

What does this PR do?

The Git info command always passed --no-merges to git log, so the reported revision could differ
from the actual HEAD in merge-based release workflows. This surfaced downstream as a regression in
buildnumber-maven-plugin#229 (which
switched from git rev-parse --verify HEAD to git log -1 --no-merges).

As requested in #1327, this makes the behavior configurable via a new
CommandParameter.SCM_SKIP_MERGE_COMMITS parameter ("skipMergeCommits"):

• Default true — skip merge commits (current behavior, fully backward compatible).
• Set to false to include merge commits, so the reported revision matches the actual HEAD.

Changes

• maven-scm-api — new public CommandParameter.SCM_SKIP_MERGE_COMMITS (@since 2.2.2).
• maven-scm-provider-gitexe — GitInfoCommand adds --no-merges only when the flag is true
  (null-safe reader mirroring the existing shortRevisionLength handling, plus a
  DEFAULT_SKIP_MERGE_COMMITS constant).
• maven-scm-provider-jgit — JGitInfoCommand now honors the same flag by applying
  RevFilter.NO_MERGES for both the HEAD and the per-file lookups. Previously the JGit provider
  never filtered merge commits, diverging from gitexe; it is now consistent with it (with the
  default true, JGit skips merge commits as gitexe already did).

Tests

• GitInfoCommandTest (gitexe): asserts --no-merges is present by default and absent when
  skipMergeCommits=false.
• New JGitInfoCommandTest: builds a repository whose HEAD is a no-fast-forward merge commit and
  verifies that the merge commit is reported when skipMergeCommits=false and skipped by default.
• The existing Info command TCK tests (which pass null parameters) keep passing, confirming the
  default behavior is unchanged for both providers.

Notes

This is the enabling change on the maven-scm side. To fully address buildnumber-maven-plugin#229, the
plugin will need to expose an option that sets SCM_SKIP_MERGE_COMMITS = false on the
CommandParameters it passes to ScmProvider#info.

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Build note: mvn verify is green for the modules touched by this PR (maven-scm-api,
maven-scm-provider-gitexe, maven-scm-provider-jgit), including Checkstyle, Spotless and
Apache RAT. The only failures observed locally are 5 pre-existing JGit hook-rejection TCK tests
(testPushBranchRejected, JGitCheckIn*#testCommitWithRejectingPreCommitHook, testPushTagRejected,
testPushTagDeletionRejected) that fail identically on a clean master, because git hooks do not
fire in my local Windows environment — unrelated to this change. The integration tests
(-Prun-its) were not run locally.

Fixes #1327

[GabriRuflex]

cc @kwin — would you have time to review this small enabling change for #1327 (make --no-merges configurable in the Git info command)? Thanks!

[GabriRuflex]

cc @kwin — would you have time to review this small enabling change for #1327 (make --no-merges configurable in the Git info command)? Thanks!

Hey @slachiewicz could you please take a look to this PR?
Thanks a lot!

[Copilot]

Pull request overview

Adds a new skipMergeCommits command parameter to make Git info revision selection configurable, addressing cases where always using --no-merges causes the reported revision to differ from HEAD in merge-based workflows.

Changes:

• Introduces new public CommandParameter.SCM_SKIP_MERGE_COMMITS (defaulting to true for backward compatibility).
• Updates gitexe GitInfoCommand to conditionally add --no-merges based on the parameter.
• Updates JGit JGitInfoCommand to apply merge-skipping consistently (including per-path lookups) and adds provider-level tests.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
maven-scm-providers/maven-scm-providers-git/maven-scm-provider-jgit/src/test/java/org/apache/maven/scm/provider/git/jgit/command/info/JGitInfoCommandTest.java	Adds unit tests for default merge-skipping and opt-in merge inclusion behavior.
maven-scm-providers/maven-scm-providers-git/maven-scm-provider-jgit/src/main/java/org/apache/maven/scm/provider/git/jgit/command/info/JGitInfoCommand.java	Adds parameter handling to optionally apply RevFilter.NO_MERGES and align behavior with gitexe.
maven-scm-providers/maven-scm-providers-git/maven-scm-provider-gitexe/src/test/java/org/apache/maven/scm/provider/git/gitexe/command/info/GitInfoCommandTest.java	Adds assertions verifying --no-merges default and its absence when disabled.
maven-scm-providers/maven-scm-providers-git/maven-scm-provider-gitexe/src/main/java/org/apache/maven/scm/provider/git/gitexe/command/info/GitInfoCommand.java	Conditionally adds --no-merges based on the new parameter while preserving default behavior.
maven-scm-api/src/main/java/org/apache/maven/scm/CommandParameter.java	Adds the new SCM_SKIP_MERGE_COMMITS public parameter definition (@since 2.2.2).

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[GabriRuflex]

All fixed and tested

[GabriRuflex]

@slachiewicz The Copilot review has been completed and all its remarks have been addressed.

While the scope of this enhancement is intentionally limited, it is the prerequisite for fixing mojohaus/buildnumber-maven-plugin#229, where the --no-merges behavior introduced in #193 causes the plugin to generate a revision that no longer matches the actual SCM version for workflows relying on merge commits.

Making this behavior configurable was also suggested by @kwin in that issue.

I'd appreciate a review when someone has a chance.
Happy to rebase or adjust anything if needed. Thanks!

[kwin]

Looks good, thanks. Can we move the test to GitInfoCommandTckTest to make sure it is executed for all GitInfo impls in the same way? That should also reduce code duplication.

[GabriRuflex]

@kwin Done — the behavioral tests now live in GitInfoCommandTckTest so they run identically for both gitexe and JGit (the provider-specific tests were removed).