vercel / has-changed-path

GitHub Action that saves time and money in monorepo environments

Has Changed Path - GitHub Action

This action outputs whether a path or combination of paths has changed in the previous commit.

It solves a common issue among monorepo setups: conditional actions. Deploying a project that did not change in the previous commit could be a waste of time and resources.

With this action, you know if a deployment or any other job needs to run based on the changed paths of the most recent commit.

It differs from GitHub's paths as our action is meant to be used inside your job steps, not at the root of your workflow file (see this issue).

My recommendation is to put this action in a workflow that runs on every push to master.

Inputs

• paths (required): Path to detect changes. It's possible to pass one path, a combination or a wildcard. Valid options include: packages/front, packages/front packages/shared, packages/**/tests. See workflow examples below for more information.

Outputs

• changed: boolean indicating if the paths changed at the latest commit

Example workflows

Important info:

Notice that you must configure fetch-depth in your actions/checkout@v2. That's because their default option now is to fetch only the latest commit instead of all history (more info)

If you want to fetch all history, pass fetch-depth: 0.

For monorepo packages, where history tends to be larger than single repos, it may take a while fetching all of it. That's why we used fetch-depth: 100 in the examples. It will fetch the latest 100 commits.

Detecting a simple one-path change:

name: Conditional Deploy

on: push

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v2
        with:
          fetch-depth: 100

      - uses: marceloprado/has-changed-path@v1
        id: changed-front
        with:
          paths: packages/front

      - name: Deploy front
        if: steps.changed-front.outputs.changed == 'true'
        run: /deploy-front.sh

Detecting changes in multiple paths:

Useful when you have dependencies between packages (eg. /common package used in /front and /server). Below, the output would be truthy for any given change inside packages/front or packages/common.

name: Conditional Deploy

on: push

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v2
        with:
          fetch-depth: 100

      - uses: marceloprado/has-changed-path@v1
        id: changed-front
        with:
          paths: packages/front packages/common

      - name: Deploy front
        if: steps.changed-front.outputs.changed == 'true'
        run: /deploy-front.sh

Detecting a one-path change with checkout multiple repos:

name: Conditional Deploy

on: push

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v2
        with:
          fetch-depth: 100
          path: main

      - uses: actions/checkout@v2
        with:
          fetch-depth: 100
          repsitory: my-org/my-tools
          path: my-tools

      - uses: marceloprado/has-changed-path@v1
        id: changed-main
        with:
          paths: packages/front
        env:
          SOURCE: main

      - uses: marceloprado/has-changed-path@v1
        id: changed-my-tools
        with:
          paths: somewhere/else
        env:
          SOURCE: my-tools

      - name: Deploy main
        if: steps.changed-main.outputs.changed == 'true'
        run: /deploy-main.sh

      - name: Deploy my tools
        if: steps.changed-my-tools.outputs.changed == 'true'
        run: /deploy-my-tools.sh

How it works?

The action itself is pretty simple - take a look at src/hasChanged.js ;) .

Basically, we compare the latest HEAD with the previous one using git diff command. This allows us to effectively detect changes in most cases (squashed merges and merges with merge commit).

The algorithm works very similar with Netlify's default way for detecting changes in monorepo builds.

Contribute

Have any thoughts or suggestions? Please, open an issue and I'll be happy to improve this action!