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GitHub actions to get git diff.

1. Example workflow
   
2. Skip
   

on: pull_request
name: CI
jobs:
  eslint:
    name: ESLint
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - uses: technote-space/get-diff-action@v1
        with:
          PREFIX_FILTER: |
            src
            __tests__
          SUFFIX_FILTER: .ts
      - name: Install Package dependencies
        run: yarn install
        if: env.GIT_DIFF
      - name: Check code style
        # Check only the source codes that have differences
        run: yarn eslint ${{ env.GIT_DIFF }}
        if: env.GIT_DIFF

  phpmd:
    name: PHPMD
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - uses: technote-space/get-diff-action@v1
        id: git_diff
        with:
          SUFFIX_FILTER: .php
          SEPARATOR: ','
      - name: Install composer
        run: composer install
        if: steps.git_diff.outputs.diff
      - name: Check code style
        # Check only the source codes that have differences
        run: vendor/bin/phpmd ${{ steps.git_diff.outputs.diff }} ansi phpmd.xml
        if: steps.git_diff.outputs.diff

If there is no difference in the source code below, this workflow will skip the code style check

• src/**/*.ts
• __tests__/**/*.ts

1. Get git diff

   git diff ${FROM}${DOT}${TO} '--diff-filter=${DIFF_FILTER}' --name-only

   e.g. (default)

   DOT: '...'
   DIFF_FILTER: 'AM'

   =>

   git diff ${FROM}...${TO} '--diff-filter=AM' --name-only

   =>

   .github/workflows/ci.yml
   __tests__/utils/command.test.ts
   package.json
   src/main.ts
   src/utils/command.ts
   yarn.lock
   

   ${FROM}, ${TO}

2. Filtered by PREFIX_FILTER or SUFFIX_FILTER option

   e.g.

   SUFFIX_FILTER: .ts
   PREFIX_FILTER: src/

   =>

   src/main.ts
   src/utils/command.ts
   

3. Mapped to absolute if ABSOLUTE option is true (default: false)

   e.g.

   /home/runner/work/my-repo-name/my-repo-name/src/main.ts
   /home/runner/work/my-repo-name/my-repo-name/src/utils/command.ts
   

4. Combined by SEPARATOR option

   e.g. (default)

   SEPARATOR: ' '

   =>

   /home/runner/work/my-repo-name/my-repo-name/src/main.ts /home/runner/work/my-repo-name/my-repo-name/src/utils/command.ts
   

If called on any other event, the result will be empty.

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