fix: stat diff summary performance

[lnewson]

While investigating why running git log was taking so long for a repo (it's pretty large and there was some mass renaming). There was one commit (~4000 changed files) that was taking ~19s to parse the diff summary for and overall it would take ~40s. When running the equivalent native git command it only took ~8s.

Looking into it a bit more, I believe the main cause was that the regex is doing a lot of backtracking, especially for long filenames. So my fix was to just add ^ to make it match from the start of the line and avoid some backtracking.

Before:

> run = async () => {
  const start = performance.now();
  await simpleGit().log({ '--stat': 4906 });
  console.log('Time', performance.now() - start);
}
> await run()
Time 40318.625875

After:

> run = async () => {
  const start = performance.now();
  await simpleGit().log({ '--stat': 4906 });
  console.log('Time', performance.now() - start);
}
> await run()
Time 9392.257582999999

[changeset-bot]

🦋 Changeset detected

Latest commit: 8a3118d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
simple-git	Patch

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[steveukx]

Thank you for the detailed description and the pull request. I've now released a new version that includes this change.