Example test failure:

    $ nvim -es +"lua require('scripts.lintcommit')._test()"
    [ FAIL ]: expected=true, got=false
        input: ":no type before colon 1"
    [ FAIL ]: expected=true, got=false
        input: "ci: tab after colon"

Example main({trace=true}) output:

    $ nvim -es +"lua require('scripts.lintcommit').main()"
    run: { "git", "branch", "--show-current" }
    run: { "git", "merge-base", "origin/master", "master" }
    run: { "git", "merge-base", "upstream/master", "master" }
    run: { "git", "rev-list", "89db07556dbdce97c0c150ed7e47d80e1ddacad3..master" }
    run: { "git", "show", "-s", "--format=%s", "d2e6d2f5fc93b6da3c6153229135ba2f0b24f8cc" }
    Invalid commit message: "buildlint): commit linter #15620"
        Commit: d2e6d2f5fc93b6da3c6153229135ba2f0b24f8cc
        Invalid commit type "buildlint)". Allowed types are:
        { "build", "ci", "docs", "feat", "fix", "perf", "refactor", "revert", "test", "chore", "vim-patch" }
        See also:
            https://github.com/neovim/neovim/blob/master/CONTRIBUTING.md#commit-messages
            https://www.conventionalcommits.org/en/v1.0.0/