feat: filter commits by message

[TrebledJ]

This PR adds options to getGitCommitDateFromPath which allows fine-grained filtering to select commits which (presumably) update content. This enables programmers who have OCD set patterns and are stringent with commit messages to select more appropriate "last modified" dates.

Example

Suppose I commit content-changes with the pattern feat: updated post. I can filter commits using

getGitCommitDateFromPath(..., { keep: /^feat:/ });

Suppose I use these other patterns: chore: updated css, bugfix: fixed logic. I can exclude these commits using:

getGitCommitDateFromPath(..., { ignore: /^(bugfix|chore):/ });

These features might be a bit niche, but I thought it'd be a nice addition to this repo, in case others were looking for something similar.

Notes

• This only checks the commit subject, not the body.
• Slower with options, since we use --follow to follow renames. If no options are provided, roughly the same speed.
• I didn't use the git log --grep option, since it is buggy in conjunction with --follow. The workaround implemented is to grab all commits (no -1 flag) and manually filter with JS.