pre-commit started as a framework for running linters and code formatters during git actions via git hooks. It's grown and expanded and now supports an extensive list of languages and actions and manual running of actions. But even at it's core, it's great for letting computers nitpick about whitespace and formatting, so that code reviews can focus on architecture and design.
Anthony Sottile discusses pre-commit, for using locally by developers, and pre-commit.ci, which can run actions during merge requests.
"Git hook scripts are useful for identifying simple issues before submission to code review. We run our hooks on every commit to automatically point out issues in code such as missing semicolons, trailing whitespace, and debug statements. By pointing these issues out before code review, this allows a code reviewer to focus on the architecture of a change while not wasting time with trivial style nitpicks." - pre-commit.com
"Developers spend a fair chunk of time during their development flow fixing relatively trivial problems in their code. pre-commit.ci both enforces that these issues are discovered, which is opt in for each developer workflow via pre-commit, but also fixes the issues automatically, letting developers focus their time on more valuable problems." - A user of pre-commit.ci