Commit Messages With Monorepo Scopes

I'm lazy - when I see my friends doing things I want to do but I know I can't be bothered to put the work in, I just automate a rough approximation.

@alloy nearly always marks his commits with a context, e.g.

• [overrides] Add Dimensions typings
• [package] Actually use our own generated files
• [polyfill] Make $TypeOf also return the class

This is cool, yeah, but I'm not going to remember to do this. Instead what I've been doing is automating that via git hooks.

As I'm mostly in JS projects, I use husky v4 to set up my hooks:

json
{
  "husky": {
    "hooks": {
      "pre-commit": "yarn test && yarn danger local --dangerfile dangerfile.local.ts --staging",
      "pre-push": "yarn build && yarn test",
      "prepare-commit-msg": "node scripts/prefixCommitMsg.mjs"
    }
  },
}

The key one being prepare-commit-msg which runs a JS script:

js
// @ts-check
import fs from "fs"
import { execSync } from "child_process"
 
const fileToEdit = process.env.HUSKY_GIT_PARAMS.split(" ")[0]
const files = execSync("git status --porcelain", { encoding: "utf8" })
 
const maps = {
  "spelltower/": "SPTWR",
  "typeshift/": "TPSFT",
}
 
const prefixes = new Set()
files.split("\n").forEach(f => {
  const found = Object.keys(maps).find(prefix => f.includes(prefix))
  if (found) prefixes.add(maps[found])
})
 
if (prefixes.size) {
  const prefix = [...prefixes.values()].sort().join(", ")
  const msg = fs.readFileSync(fileToEdit, "utf8")
  if (!msg.includes(prefix)) {
    fs.writeFileSync(fileToEdit, `[${prefix}] ${msg}`)
  }
}

This JS script looks up what files were changed in the commit (via git status), and then adds a set of prefixes to the commit message.

E.g. I make a change to games/spelltower/app.ts then [SPTWR] is automatically added to commit message.