Let callers opt out of the GitProvenance committer-history walk

[knutwannheden]

Motivation

GitProvenance.fromProjectDirectory(...) unconditionally calls getCommitters(repository), which does an unbounded git.log() walk over the entire commit history. There is no flag, env gate, or bound on it.

Many callers consume only getOrigin()/getRepositoryOrigin()/getRepositoryPath()/getBranch()/getChange() and never read committers — for them the walk is pure waste. CPU profiling of CommonStaticAnalysis over a ~40k-commit repository (spring-boot) attributed ~11% of the whole run to GitProvenance.getCommitters → JGit PackIndex binary search. This PR lets such callers opt out of the walk.

Examples

// Existing behavior — walks full history to populate committers (unchanged):
GitProvenance withCommitters =
    GitProvenance.fromProjectDirectory(projectDir, environment, gitRemoteParser);

// New overload — skip the committer walk; getCommitters() returns an empty list.
// origin/branch/change/autocrlf/eol/remote are identical to the call above.
GitProvenance fast =
    GitProvenance.fromProjectDirectory(projectDir, environment, gitRemoteParser, /* includeCommitters */ false);

Summary

• Added a public overload fromProjectDirectory(Path, BuildEnvironment, GitRemote.Parser, boolean includeCommitters).
• The existing three-arg overload delegates to it with includeCommitters = true, so all existing overloads keep current behavior.
• Threaded includeCommitters through both private fromGitConfig methods (including the Jenkins branch). When false, the committer field is populated with emptyList() instead of getCommitters(repository), skipping the history walk.
• Everything else (origin, branch, change, autocrlf, eol, remote) is unchanged, so GitProvenance.equals, RepositoryId derivation, and serialized markers stay byte-identical for committer-consuming callers.

Out of scope / follow-ups

• Even the committer-including path is unbounded. The only first-party consumer (FindCommitters) bounds to 90 days; adding a since/limit parameter could be a follow-up.
• A downstream consumer can now drop its hand-rolled reimplementation of the cheap git-config read path in favor of this overload.

Test plan

• New GitProvenanceTest.excludeCommittersMatchesIncludingPath: on a normal branch checkout, asserts the opt-out overload produces a GitProvenance whose origin/branch/change match the committer-including path, with a non-empty committers list on the including path (proving the walk ran) and an empty list on the opt-out path (proving it was skipped).
• Existing GitProvenanceTest stays green: 59 tests, 2 @Disabled skipped, 0 failures, 0 errors.