Example GH action to deploy only changed functions to Firebase

action.yml

name: example action

on:
  push:
    branches: [ dev ]
  pull_request:
    branches: [ master ]

jobs:

  deploy-functions:
    name: deploy functions
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
        with:
          fetch-depth: "2" # must be 2 to grab previous level
     ## Following step checks all directories in functions/ for any changed files -- i.e. any updated functions.
      - name: get changed functions
        id: changed-functions
        uses: tj-actions/changed-files@v14.2
        with:
          files: |
            functions/*/
     ## Use node and NPM install here ##
     ## Set firebase function env variables.##
     
     # 1. The "...all_changed_files" file contains a space-separated list of changed files (with absolute paths)
     # 2. Use sed to grab the folder name, e.g. 'funcAdd' in functions/funcAdd/index.js
     # 3. sed again to wrap that in the appropriate syntax for firebase deploys, e.g. functions:funcAdd,functions:funcSub,
      - name: build deploy string
        run: |
          echo "CHANGED_OUTPUT=$(echo "${{steps.changed-functions.outputs.all_changed_files}}" | sed 's/functions\/\([[:alpha:]]\+\)\/index.js/\1/g' | sed 's/\([[:alpha:]]\+\)[[:space:]]\?/functions:\1,/g')" >> $GITHUB_ENV
      # Prints the final deploy string, for debugging
      - name: print deploy string
        run: |
          echo $CHANGED_OUTPUT
       # passes the constructed string to the deploy argument. Will not deploy any functions if none have changed.
      - name: deploy functions
        uses: w9jds/firebase-action@master
        if: steps.changed-functions.outputs.any_changed == 'true'
        with:
          args: deploy --only ${{env.CHANGED_OUTPUT}}
          # etc...