Improve change detection for feature branches (#16)

* Detect changes against configured base branch

* Update README and action.yml

* Add job.outputs example

* Update CHANGELOG

.eslintrc.json

@@ -25,7 +25,7 @@
       "@typescript-eslint/generic-type-naming": ["error", "^[A-Z][A-Za-z]*$"],
       "@typescript-eslint/no-array-constructor": "error",
       "@typescript-eslint/no-empty-interface": "error",
-      "@typescript-eslint/no-explicit-any": "error",
+      "@typescript-eslint/no-explicit-any": "off",
       "@typescript-eslint/no-extraneous-class": "error",
       "@typescript-eslint/no-for-in-array": "error",
       "@typescript-eslint/no-inferrable-types": "error",
@@ -42,7 +42,7 @@
       "@typescript-eslint/prefer-includes": "error",
       "@typescript-eslint/prefer-interface": "error",
       "@typescript-eslint/prefer-string-starts-ends-with": "error",
-      "@typescript-eslint/promise-function-async": "error",
+      "@typescript-eslint/promise-function-async": ["error", { "allowAny": true }],
       "@typescript-eslint/require-array-sort-compare": "error",
       "@typescript-eslint/restrict-plus-operands": "error",
       "semi": "off",

.github/workflows/build.yml

@@ -12,3 +12,15 @@ jobs:
     - run: |
         npm install
         npm run all
+
+  self-test:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: ./
+      id: filter
+      with:
+        filters: '.github/filters.yml'
+    - name: filter-test
+      if: steps.filter.outputs.any != 'true' || steps.filter.outputs.error == 'true'
+      run: exit 1

.github/workflows/pull-request-verification.yml

@@ -1,9 +1,6 @@
 name: "Pull Request Verification"
 on:
   pull_request:
-    types:
-      - opened
-      - synchronize
     branches:
       - master
 

CHANGELOG.md

@@ -0,0 +1,21 @@
+# Changelog
+
+## v2.2.0
+- [Improve change detection for feature branches](https://github.com/dorny/paths-filter/pull/16)
+
+## v2.1.0
+- [Support reusable paths blocks with yaml anchors](https://github.com/dorny/paths-filter/pull/13)
+
+## v2.0.0
+- [Added support for workflows triggered by push events](https://github.com/dorny/paths-filter/pull/10)
+- Action and repository renamed to paths-filter - original name doesn't make sense anymore
+
+## v1.1.0
+- [Allows filters to be specified in own .yml file](https://github.com/dorny/paths-filter/pull/8)
+- [Adds alternative change detection using git fetch and git diff-index](https://github.com/dorny/paths-filter/pull/9)
+
+## v1.0.1
+Updated dependencies - fixes github security alert
+
+## v1.0.0
+First official release uploaded to marketplace.

LICENSE

@@ -1,7 +1,7 @@
 
 The MIT License (MIT)
 
-Copyright (c) 2018 GitHub, Inc. and contributors
+Copyright (c) 2020 Michal Dorner and contributors
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -1,27 +1,34 @@
 <p align="center">
-  <a href="https://github.com/dorny/pr-changed-files-filter/actions"><img alt="typescript-action status" src="https://github.com/dorny/pr-changed-files-filter/workflows/Build/badge.svg"></a>
+  <a href="https://github.com/dorny/paths-filter/actions"><img alt="paths-filter status" src="https://github.com/dorny/paths-filter/workflows/Build/badge.svg"></a>
 </p>
 
-**CAUTION**: This action can be only used in a workflow triggered by `pull_request` event.
+# Paths filter
 
-# Pull request changed files filter
+With this [Github Action](https://github.com/features/actions) you can execute your workflow steps only if relevant files are modified.
 
-This [Github Action](https://github.com/features/actions) enables conditional execution of workflow job steps considering which files are modified by a pull request.
-
-It saves time and resources especially in monorepo setups, where you can run slow tasks (e.g. integration tests) only for changed components.
-Github workflows built-in
-[path filters](https://help.github.com/en/actions/referenceworkflow-syntax-for-github-actions#onpushpull_requestpaths)
+It saves time and resources especially in monorepo setups, where you can run slow tasks (e.g. integration tests or deployments) only for changed components.
+Github workflows built-in [path filters](https://help.github.com/en/actions/reference/workflow-syntax-for-github-actions#onpushpull_requestpaths)
 doesn't allow this because they doesn't work on a level of individual jobs or steps.
 
+Supported workflows:
+- Action triggered by **[pull_request](https://help.github.com/en/actions/reference/events-that-trigger-workflows#pull-request-event-pull_request)** event:
+  - changes detected against the pull request base branch
+- Action triggered by **[push](https://help.github.com/en/actions/reference/events-that-trigger-workflows#push-event-push)** event:
+  - changes detected against the most recent commit on the same branch before the push
+  - changes detected against the top of the configured *base* branch (e.g. master)
+
 ## Usage
 
-The action accepts filter rules in the YAML format.
+Filter rules are defined using YAML format.
 Each filter rule is a list of [glob expressions](https://github.com/isaacs/minimatch).
 Corresponding output variable will be created to indicate if there's a changed file matching any of the rule glob expressions.
 Output variables can be later used in the `if` clause to conditionally run specific steps.
 
 ### Inputs
-- **`token`**: GitHub Access Token - defaults to `${{ github.token }}`
+- **`token`**: GitHub Access Token - defaults to `${{ github.token }}` so you don't have to explicitly provide it.
+- **`base`**: Git reference (e.g. branch name) against which the changes will be detected. Defaults to repository default branch (e.g. master).
+              If it references same branch it was pushed to, changes are detected against the most recent commit before the push.
+              This option is ignored if action is triggered by *pull_request* event.
 - **`filters`**: Path to the configuration file or directly embedded string in YAML format. Filter configuration is a dictionary, where keys specifies rule names and values are lists of file path patterns.
 
 ### Outputs
@@ -29,20 +36,20 @@ Output variables can be later used in the `if` clause to conditionally run speci
    - `'true'` - if **any** of changed files matches any of rule patterns
    - `'false'` - if **none** of changed files matches any of rule patterns
 
-
 ### Notes
 - minimatch [dot](https://www.npmjs.com/package/minimatch#dot) option is set to true - therefore
   globbing will match also paths where file or folder name starts with a dot.
+- You can use YAML anchors to reuse path expression(s) inside another rule. See example in the tests.
+- If changes are detected against the previous commit and there is none (i.e. first push of a new branch), all filter rules will report changed files.
+- You can use `base: ${{ github.ref }}` to configure change detection against previous commit for every branch you create.
 
-### Sample workflow
+### Example
 ```yaml
-name: Build verification
-
 on:
+  push:
+    branches:
+      - master
   pull_request:
-    types:
-      - opened
-      - synchronize
     branches:
       - master
 jobs:
@@ -50,7 +57,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
-    - uses: dorny/pr-changed-files-filter@v1
+    - uses: dorny/paths-filter@v2.2.0
       id: filter
       with:
         # inline YAML or path to separate file (e.g.: .github/filters.yaml)
@@ -76,20 +83,55 @@ jobs:
       run: ...
 ```
 
+If your workflow uses multiple jobs, you can put *paths-filter* into own job and use
+[job outputs](https://help.github.com/en/actions/reference/workflow-syntax-for-github-actions#jobsjobs_idoutputs)
+in other jobs [if](https://help.github.com/en/actions/reference/workflow-syntax-for-github-actions#jobsjob_idif) statements:
+```yml
+on:
+  pull_request:
+    branches:
+      - master
+jobs:
+  changes:
+    runs-on: ubuntu-latest
+    # Set job outputs to values from filter step
+    outputs:
+      backend: ${{ steps.filter.outputs.backend }}
+      frontend: ${{ steps.filter.outputs.frontend }}
+    steps:
+    # For pull requests it's not necessary to checkout the code
+    - uses: dorny/paths-filter@v2.2.0
+      id: filter
+      with:
+        # Filters stored in own yaml file
+        filters: '.github/filters.yml'
+  backend:
+    if: ${{ needs.changes.outputs.backend == 'true' }}
+    steps:
+      - ...
+  frontend:
+    if: ${{ needs.changes.outputs.frontend == 'true' }}
+    steps:
+      - ...
+```
+
 ## How it works
 
-1. Required inputs are checked (`filters`)
-2. If token was provided, it's used to fetch list of changed files from Github API.
-3. If token was not provided, base branch is fetched and changed files are detected using `git diff-index` command.
-4. For each filter rule it checks if there is any matching file
-5. Output variables are set
+1. If action was triggered by pull request:
+   - If access token was provided it's used to fetch list of changed files from Github API.
+   - If access token was not provided, top of the base branch is fetched and changed files are detected using `git diff-index <SHA>` command.
+2. If action was triggered by push event
+   - if *base* input parameter references same branch it was pushed to, most recent commit before the push is fetched
+   - If *base* input parameter references other branch, top of that branch is fetched
+   - changed files are detected using `git diff-index FETCH_HEAD` command.
+3. For each filter rule it checks if there is any matching file
+4. Output variables are set
 
-## Difference from related projects:
+## Difference from similar projects:
 
 - [Has Changed Path](https://github.com/MarceloPrado/has-changed-path)
   - detects changes from previous commit
   - you have to configure `checkout` action to fetch some number of previous commits
-  - `git diff` is used for change detection
   - outputs only single `true` / `false` value if any of provided paths contains changes
 - [Changed Files Exporter](https://github.com/futuratrepadeira/changed-files)
   - outputs lists with paths of created, updated and deleted files
@@ -97,4 +139,4 @@ jobs:
 - [Changed File Filter](https://github.com/tony84727/changed-file-filter)
   - allows change detection between any refs or commits
   - fetches whole history of your git repository
-  - might have negative performance impact on big repositories (github by default fetches only single commit)
+  - might have negative performance impact on big repositories (github by default fetches only single commit)

__tests__/filter.test.ts

@@ -90,4 +90,18 @@ describe('matching tests', () => {
     const match = filter.match(['.test/.test.js'])
     expect(match.dot).toBeTruthy()
   })
+
+  test('matches path based on rules included using YAML anchor', () => {
+    const yaml = `
+    shared: &shared
+      - common/**/*
+      - config/**/*
+    src:
+      - *shared
+      - src/**/*
+    `
+    let filter = new Filter(yaml)
+    const match = filter.match(['config/settings.yml'])
+    expect(match.src).toBeTruthy()
+  })
 })

__tests__/git.test.ts

@@ -0,0 +1,19 @@
+import * as git from '../src/git'
+
+describe('git utility function tests (those not invoking git)', () => {
+  test('Detects if ref references a tag', () => {
+    expect(git.isTagRef('refs/tags/v1.0')).toBeTruthy()
+    expect(git.isTagRef('refs/heads/master')).toBeFalsy()
+    expect(git.isTagRef('master')).toBeFalsy()
+  })
+  test('Trims "refs/" from ref', () => {
+    expect(git.trimRefs('refs/heads/master')).toBe('heads/master')
+    expect(git.trimRefs('heads/master')).toBe('heads/master')
+    expect(git.trimRefs('master')).toBe('master')
+  })
+  test('Trims "refs/" and "heads/" from ref', () => {
+    expect(git.trimRefsHeads('refs/heads/master')).toBe('master')
+    expect(git.trimRefsHeads('heads/master')).toBe('master')
+    expect(git.trimRefsHeads('master')).toBe('master')
+  })
+})

action.yml

@@ -1,11 +1,17 @@
-name: 'Pull request changed files filter'
-description: 'Enables conditional execution of workflow job steps considering which files are modified by a pull request.'
+name: 'Paths filter'
+description: 'Execute your workflow steps only if relevant files are modified.'
 author: 'Michal Dorner <dorner.michal@gmail.com>'
 inputs:
   token:
     description: 'GitHub Access Token'
     required: false
     default: ${{ github.token }}
+  base:
+    description: |
+      Git reference (e.g. branch name) against which the changes will be detected. Defaults to repository default branch (e.g. master).
+      If it references same branch it was pushed to, changes are detected against the most recent commit before the push.
+      This option is ignored if action is triggered by pull_request event.
+    required: false
   filters:
     description: 'Path to the configuration file or YAML string with filters definition'
     required: true

dist/index.js

@@ -3798,27 +3798,29 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
     });
 };
 Object.defineProperty(exports, "__esModule", { value: true });
-exports.getChangedFiles = exports.fetchBranch = void 0;
+exports.trimRefsHeads = exports.trimRefs = exports.isTagRef = exports.getChangedFiles = exports.fetchCommit = exports.FETCH_HEAD = exports.NULL_SHA = void 0;
 const exec_1 = __webpack_require__(986);
-function fetchBranch(base) {
+exports.NULL_SHA = '0000000000000000000000000000000000000000';
+exports.FETCH_HEAD = 'FETCH_HEAD';
+function fetchCommit(ref) {
     return __awaiter(this, void 0, void 0, function* () {
-        const exitCode = yield exec_1.exec('git', ['fetch', '--depth=1', 'origin', base]);
+        const exitCode = yield exec_1.exec('git', ['fetch', '--depth=1', '--no-tags', 'origin', ref]);
         if (exitCode !== 0) {
-            throw new Error(`Fetching branch ${base} failed, exiting`);
+            throw new Error(`Fetching ${ref} failed`);
         }
     });
 }
-exports.fetchBranch = fetchBranch;
-function getChangedFiles(base) {
+exports.fetchCommit = fetchCommit;
+function getChangedFiles(ref) {
     return __awaiter(this, void 0, void 0, function* () {
         let output = '';
-        const exitCode = yield exec_1.exec('git', ['diff-index', '--name-only', base], {
+        const exitCode = yield exec_1.exec('git', ['diff-index', '--name-only', ref], {
             listeners: {
                 stdout: (data) => (output += data.toString())
             }
         });
         if (exitCode !== 0) {
-            throw new Error(`Couldn't determine changed files, exiting`);
+            throw new Error(`Couldn't determine changed files`);
         }
         return output
             .split('\n')
@@ -3827,6 +3829,22 @@ function getChangedFiles(base) {
     });
 }
 exports.getChangedFiles = getChangedFiles;
+function isTagRef(ref) {
+    return ref.startsWith('refs/tags/');
+}
+exports.isTagRef = isTagRef;
+function trimRefs(ref) {
+    return trimStart(ref, 'refs/');
+}
+exports.trimRefs = trimRefs;
+function trimRefsHeads(ref) {
+    const trimRef = trimStart(ref, 'refs/');
+    return trimStart(trimRef, 'heads/');
+}
+exports.trimRefsHeads = trimRefsHeads;
+function trimStart(ref, start) {
+    return ref.startsWith(start) ? ref.substr(start.length) : ref;
+}
 
 
 /***/ }),
@@ -4485,16 +4503,20 @@ function run() {
             const token = core.getInput('token', { required: false });
             const filtersInput = core.getInput('filters', { required: true });
             const filtersYaml = isPathInput(filtersInput) ? getConfigFileContent(filtersInput) : filtersInput;
-            if (github.context.eventName !== 'pull_request') {
-                core.setFailed('This action can be triggered only by pull_request event');
-                return;
-            }
-            const pr = github.context.payload.pull_request;
             const filter = new filter_1.default(filtersYaml);
-            const files = token ? yield getChangedFilesFromApi(token, pr) : yield getChangedFilesFromGit(pr);
-            const result = filter.match(files);
-            for (const key in result) {
-                core.setOutput(key, String(result[key]));
+            const files = yield getChangedFiles(token);
+            if (files === null) {
+                // Change detection was not possible
+                // Set all filter keys to true (i.e. changed)
+                for (const key in filter.rules) {
+                    core.setOutput(key, String(true));
+                }
+            }
+            else {
+                const result = filter.match(files);
+                for (const key in result) {
+                    core.setOutput(key, String(result[key]));
+                }
             }
         }
         catch (error) {
@@ -4514,13 +4536,47 @@ function getConfigFileContent(configPath) {
     }
     return fs.readFileSync(configPath, { encoding: 'utf8' });
 }
+function getChangedFiles(token) {
+    return __awaiter(this, void 0, void 0, function* () {
+        if (github.context.eventName === 'pull_request') {
+            const pr = github.context.payload.pull_request;
+            return token ? yield getChangedFilesFromApi(token, pr) : yield getChangedFilesFromGit(pr.base.sha);
+        }
+        else if (github.context.eventName === 'push') {
+            return getChangedFilesFromPush();
+        }
+        else {
+            throw new Error('This action can be triggered only by pull_request or push event');
+        }
+    });
+}
+function getChangedFilesFromPush() {
+    return __awaiter(this, void 0, void 0, function* () {
+        const push = github.context.payload;
+        // No change detection for pushed tags
+        if (git.isTagRef(push.ref))
+            return null;
+        // Get base from input or use repo default branch.
+        // It it starts with 'refs/', it will be trimmed (git fetch refs/heads/<NAME> doesn't work)
+        const baseInput = git.trimRefs(core.getInput('base', { required: false }) || push.repository.default_branch);
+        // If base references same branch it was pushed to, we will do comparison against the previously pushed commit.
+        // Otherwise changes are detected against the base reference
+        const base = git.trimRefsHeads(baseInput) === git.trimRefsHeads(push.ref) ? push.before : baseInput;
+        // There is no previous commit for comparison
+        // e.g. change detection against previous commit of just pushed new branch
+        if (base === git.NULL_SHA)
+            return null;
+        return yield getChangedFilesFromGit(base);
+    });
+}
 // Fetch base branch and use `git diff` to determine changed files
-function getChangedFilesFromGit(pullRequest) {
+function getChangedFilesFromGit(ref) {
     return __awaiter(this, void 0, void 0, function* () {
         core.debug('Fetching base branch and using `git diff-index` to determine changed files');
-        const baseRef = pullRequest.base.ref;
-        yield git.fetchBranch(baseRef);
-        return yield git.getChangedFiles(pullRequest.base.sha);
+        yield git.fetchCommit(ref);
+        // FETCH_HEAD will always point to the just fetched commit
+        // No matter if ref is SHA, branch or tag name or full git ref
+        return yield git.getChangedFiles(git.FETCH_HEAD);
     });
 }
 // Uses github REST api to get list of files changed in PR
@@ -4645,10 +4701,11 @@ class Filter {
             dot: true
         };
         for (const name of Object.keys(doc)) {
-            const patterns = doc[name];
-            if (!Array.isArray(patterns)) {
+            const patternsNode = doc[name];
+            if (!Array.isArray(patternsNode)) {
                 this.throwInvalidFormatError();
             }
+            const patterns = flat(patternsNode);
             if (!patterns.every(x => typeof x === 'string')) {
                 this.throwInvalidFormatError();
             }
@@ -4669,6 +4726,11 @@ class Filter {
     }
 }
 exports.default = Filter;
+// Creates a new array with all sub-array elements recursively concatenated
+// In future could be replaced by Array.prototype.flat (supported on Node.js 11+)
+function flat(arr) {
+    return arr.reduce((acc, val) => acc.concat(Array.isArray(val) ? flat(val) : val), []);
+}
 
 
 /***/ }),

package-lock.json

@@ -1,5 +1,5 @@
 {
-  "name": "pr-changed-files-filter",
+  "name": "paths-filter",
   "version": "1.0.0",
   "lockfileVersion": 1,
   "requires": true,
@@ -3897,33 +3897,33 @@
       }
     },
     "@typescript-eslint/experimental-utils": {
-      "version": "3.0.0",
-      "resolved": "https://registry.npmjs.org/@typescript-eslint/experimental-utils/-/experimental-utils-3.0.0.tgz",
-      "integrity": "sha512-BN0vmr9N79M9s2ctITtChRuP1+Dls0x/wlg0RXW1yQ7WJKPurg6X3Xirv61J2sjPif4F8SLsFMs5Nzte0WYoTQ==",
+      "version": "3.3.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/experimental-utils/-/experimental-utils-3.3.0.tgz",
+      "integrity": "sha512-d4pGIAbu/tYsrPrdHCQ5xfadJGvlkUxbeBB56nO/VGmEDi/sKmfa5fGty5t5veL1OyJBrUmSiRn1R1qfVDydrg==",
       "dev": true,
       "requires": {
         "@types/json-schema": "^7.0.3",
-        "@typescript-eslint/typescript-estree": "3.0.0",
+        "@typescript-eslint/typescript-estree": "3.3.0",
         "eslint-scope": "^5.0.0",
         "eslint-utils": "^2.0.0"
       }
     },
     "@typescript-eslint/parser": {
-      "version": "3.0.0",
-      "resolved": "https://registry.npmjs.org/@typescript-eslint/parser/-/parser-3.0.0.tgz",
-      "integrity": "sha512-8RRCA9KLxoFNO0mQlrLZA0reGPd/MsobxZS/yPFj+0/XgMdS8+mO8mF3BDj2ZYQj03rkayhSJtF1HAohQ3iylw==",
+      "version": "3.3.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/parser/-/parser-3.3.0.tgz",
+      "integrity": "sha512-a7S0Sqn/+RpOOWTcaLw6RD4obsharzxmgMfdK24l364VxuBODXjuJM7ImCkSXEN7oz52aiZbXSbc76+2EsE91w==",
       "dev": true,
       "requires": {
         "@types/eslint-visitor-keys": "^1.0.0",
-        "@typescript-eslint/experimental-utils": "3.0.0",
-        "@typescript-eslint/typescript-estree": "3.0.0",
+        "@typescript-eslint/experimental-utils": "3.3.0",
+        "@typescript-eslint/typescript-estree": "3.3.0",
         "eslint-visitor-keys": "^1.1.0"
       }
     },
     "@typescript-eslint/typescript-estree": {
-      "version": "3.0.0",
-      "resolved": "https://registry.npmjs.org/@typescript-eslint/typescript-estree/-/typescript-estree-3.0.0.tgz",
-      "integrity": "sha512-nevQvHyNghsfLrrByzVIH4ZG3NROgJ8LZlfh3ddwPPH4CH7W4GAiSx5qu+xHuX5pWsq6q/eqMc1io840ZhAnUg==",
+      "version": "3.3.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/typescript-estree/-/typescript-estree-3.3.0.tgz",
+      "integrity": "sha512-3SqxylENltEvJsjjMSDCUx/edZNSC7wAqifUU1Ywp//0OWEZwMZJfecJud9XxJ/40rAKEbJMKBOQzeOjrLJFzQ==",
       "dev": true,
       "requires": {
         "debug": "^4.1.1",
@@ -3956,9 +3956,9 @@
       "dev": true
     },
     "acorn": {
-      "version": "6.4.1",
-      "resolved": "https://registry.npmjs.org/acorn/-/acorn-6.4.1.tgz",
-      "integrity": "sha512-ZVA9k326Nwrj3Cj9jlh3wGFutC2ZornPNARZwsNYqQYgN0EsV2d53w5RN/co65Ohn4sUAUtb1rSUAOD6XN9idA==",
+      "version": "7.3.1",
+      "resolved": "https://registry.npmjs.org/acorn/-/acorn-7.3.1.tgz",
+      "integrity": "sha512-tLc0wSnatxAQHVHUapaHdz72pi9KUyHjq5KyHjGg9Y8Ifdc79pTh2XvI6I1/chZbnM7QtNKzh66ooDogPZSleA==",
       "dev": true
     },
     "acorn-globals": {
@@ -4003,6 +4003,12 @@
         "uri-js": "^4.2.2"
       }
     },
+    "ansi-colors": {
+      "version": "3.2.4",
+      "resolved": "https://registry.npmjs.org/ansi-colors/-/ansi-colors-3.2.4.tgz",
+      "integrity": "sha512-hHUXGagefjN2iRrID63xckIvotOXOojhQKWIPUZ4mNUZ9nLZW+7FMNoE1lOkEhNWYsx/7ysGIuJYCiMAA9FnrA==",
+      "dev": true
+    },
     "ansi-escapes": {
       "version": "3.2.0",
       "resolved": "https://registry.npmjs.org/ansi-escapes/-/ansi-escapes-3.2.0.tgz",
@@ -5419,6 +5425,15 @@
         "once": "^1.4.0"
       }
     },
+    "enquirer": {
+      "version": "2.3.5",
+      "resolved": "https://registry.npmjs.org/enquirer/-/enquirer-2.3.5.tgz",
+      "integrity": "sha512-BNT1C08P9XD0vNg3J475yIUG+mVdp9T6towYFHUv897X0KoHBjB1shyrNmhmtHWKP17iSWgo7Gqh7BBuzLZMSA==",
+      "dev": true,
+      "requires": {
+        "ansi-colors": "^3.2.1"
+      }
+    },
     "error-ex": {
       "version": "1.3.2",
       "resolved": "https://registry.npmjs.org/error-ex/-/error-ex-1.3.2.tgz",
@@ -5487,79 +5502,214 @@
       }
     },
     "eslint": {
-      "version": "5.16.0",
-      "resolved": "https://registry.npmjs.org/eslint/-/eslint-5.16.0.tgz",
-      "integrity": "sha512-S3Rz11i7c8AA5JPv7xAH+dOyq/Cu/VXHiHXBPOU1k/JAM5dXqQPt3qcrhpHSorXmrpu2g0gkIBVXAqCpzfoZIg==",
+      "version": "7.3.0",
+      "resolved": "https://registry.npmjs.org/eslint/-/eslint-7.3.0.tgz",
+      "integrity": "sha512-dJMVXwfU5PT1cj2Nv2VPPrKahKTGdX+5Dh0Q3YuKt+Y2UhdL2YbzsVaBMyG9HC0tBismlv/r1+eZqs6SMIV38Q==",
       "dev": true,
       "requires": {
         "@babel/code-frame": "^7.0.0",
-        "ajv": "^6.9.1",
-        "chalk": "^2.1.0",
-        "cross-spawn": "^6.0.5",
+        "ajv": "^6.10.0",
+        "chalk": "^4.0.0",
+        "cross-spawn": "^7.0.2",
         "debug": "^4.0.1",
         "doctrine": "^3.0.0",
-        "eslint-scope": "^4.0.3",
-        "eslint-utils": "^1.3.1",
-        "eslint-visitor-keys": "^1.0.0",
-        "espree": "^5.0.1",
-        "esquery": "^1.0.1",
+        "enquirer": "^2.3.5",
+        "eslint-scope": "^5.1.0",
+        "eslint-utils": "^2.0.0",
+        "eslint-visitor-keys": "^1.2.0",
+        "espree": "^7.1.0",
+        "esquery": "^1.2.0",
         "esutils": "^2.0.2",
         "file-entry-cache": "^5.0.1",
         "functional-red-black-tree": "^1.0.1",
-        "glob": "^7.1.2",
-        "globals": "^11.7.0",
+        "glob-parent": "^5.0.0",
+        "globals": "^12.1.0",
         "ignore": "^4.0.6",
         "import-fresh": "^3.0.0",
         "imurmurhash": "^0.1.4",
-        "inquirer": "^6.2.2",
-        "js-yaml": "^3.13.0",
+        "is-glob": "^4.0.0",
+        "js-yaml": "^3.13.1",
         "json-stable-stringify-without-jsonify": "^1.0.1",
-        "levn": "^0.3.0",
-        "lodash": "^4.17.11",
+        "levn": "^0.4.1",
+        "lodash": "^4.17.14",
         "minimatch": "^3.0.4",
-        "mkdirp": "^0.5.1",
         "natural-compare": "^1.4.0",
-        "optionator": "^0.8.2",
-        "path-is-inside": "^1.0.2",
+        "optionator": "^0.9.1",
         "progress": "^2.0.0",
-        "regexpp": "^2.0.1",
-        "semver": "^5.5.1",
-        "strip-ansi": "^4.0.0",
-        "strip-json-comments": "^2.0.1",
+        "regexpp": "^3.1.0",
+        "semver": "^7.2.1",
+        "strip-ansi": "^6.0.0",
+        "strip-json-comments": "^3.1.0",
         "table": "^5.2.3",
-        "text-table": "^0.2.0"
+        "text-table": "^0.2.0",
+        "v8-compile-cache": "^2.0.3"
       },
       "dependencies": {
-        "eslint-scope": {
-          "version": "4.0.3",
-          "resolved": "https://registry.npmjs.org/eslint-scope/-/eslint-scope-4.0.3.tgz",
-          "integrity": "sha512-p7VutNr1O/QrxysMo3E45FjYDTeXBy0iTltPFNSqKAIfjDSXC+4dj+qfyuD8bfAXrW/y6lW3O76VaYNPKfpKrg==",
+        "ansi-styles": {
+          "version": "4.2.1",
+          "resolved": "https://registry.npmjs.org/ansi-styles/-/ansi-styles-4.2.1.tgz",
+          "integrity": "sha512-9VGjrMsG1vePxcSweQsN20KY/c4zN0h9fLjqAbwbPfahM3t+NL+M9HC8xeXG2I8pX5NoamTGNuomEUFI7fcUjA==",
           "dev": true,
           "requires": {
-            "esrecurse": "^4.1.0",
-            "estraverse": "^4.1.1"
+            "@types/color-name": "^1.1.1",
+            "color-convert": "^2.0.1"
           }
         },
-        "eslint-utils": {
-          "version": "1.4.3",
-          "resolved": "https://registry.npmjs.org/eslint-utils/-/eslint-utils-1.4.3.tgz",
-          "integrity": "sha512-fbBN5W2xdY45KulGXmLHZ3c3FHfVYmKg0IrAKGOkT/464PQsx2UeIzfz1RmEci+KLm1bBaAzZAh8+/E+XAeZ8Q==",
+        "chalk": {
+          "version": "4.1.0",
+          "resolved": "https://registry.npmjs.org/chalk/-/chalk-4.1.0.tgz",
+          "integrity": "sha512-qwx12AxXe2Q5xQ43Ac//I6v5aXTipYrSESdOgzrN+9XjgEpyjpKuvSGaN4qE93f7TQTlerQQ8S+EQ0EyDoVL1A==",
           "dev": true,
           "requires": {
-            "eslint-visitor-keys": "^1.1.0"
+            "ansi-styles": "^4.1.0",
+            "supports-color": "^7.1.0"
           }
         },
+        "color-convert": {
+          "version": "2.0.1",
+          "resolved": "https://registry.npmjs.org/color-convert/-/color-convert-2.0.1.tgz",
+          "integrity": "sha512-RRECPsj7iu/xb5oKYcsFHSppFNnsj/52OVTRKb4zP5onXwVF3zVmmToNcOfGC+CRDpfK/U584fMg38ZHCaElKQ==",
+          "dev": true,
+          "requires": {
+            "color-name": "~1.1.4"
+          }
+        },
+        "color-name": {
+          "version": "1.1.4",
+          "resolved": "https://registry.npmjs.org/color-name/-/color-name-1.1.4.tgz",
+          "integrity": "sha512-dOy+3AuW3a2wNbZHIuMZpTcgjGuLU/uBL/ubcZF9OXbDo8ff4O8yVp5Bf0efS8uEoYo5q4Fx7dY9OgQGXgAsQA==",
+          "dev": true
+        },
+        "cross-spawn": {
+          "version": "7.0.3",
+          "resolved": "https://registry.npmjs.org/cross-spawn/-/cross-spawn-7.0.3.tgz",
+          "integrity": "sha512-iRDPJKUPVEND7dHPO8rkbOnPpyDygcDFtWjpeWNCgy8WP2rXcxXL8TskReQl6OrB2G7+UJrags1q15Fudc7G6w==",
+          "dev": true,
+          "requires": {
+            "path-key": "^3.1.0",
+            "shebang-command": "^2.0.0",
+            "which": "^2.0.1"
+          }
+        },
+        "eslint-visitor-keys": {
+          "version": "1.3.0",
+          "resolved": "https://registry.npmjs.org/eslint-visitor-keys/-/eslint-visitor-keys-1.3.0.tgz",
+          "integrity": "sha512-6J72N8UNa462wa/KFODt/PJ3IU60SDpC3QXC1Hjc1BXXpfL2C9R5+AU7jhe0F6GREqVMh4Juu+NY7xn+6dipUQ==",
+          "dev": true
+        },
+        "globals": {
+          "version": "12.4.0",
+          "resolved": "https://registry.npmjs.org/globals/-/globals-12.4.0.tgz",
+          "integrity": "sha512-BWICuzzDvDoH54NHKCseDanAhE3CeDorgDL5MT6LMXXj2WCnd9UC2szdk4AWLfjdgNBCXLUanXYcpBBKOSWGwg==",
+          "dev": true,
+          "requires": {
+            "type-fest": "^0.8.1"
+          }
+        },
+        "has-flag": {
+          "version": "4.0.0",
+          "resolved": "https://registry.npmjs.org/has-flag/-/has-flag-4.0.0.tgz",
+          "integrity": "sha512-EykJT/Q1KjTWctppgIAgfSO0tKVuZUjhgMr17kqTumMl6Afv3EISleU7qZUzoXDFTAHTDC4NOoG/ZxU3EvlMPQ==",
+          "dev": true
+        },
+        "levn": {
+          "version": "0.4.1",
+          "resolved": "https://registry.npmjs.org/levn/-/levn-0.4.1.tgz",
+          "integrity": "sha512-+bT2uH4E5LGE7h/n3evcS/sQlJXCpIp6ym8OWJ5eV6+67Dsql/LaaT7qJBAt2rzfoa/5QBGBhxDix1dMt2kQKQ==",
+          "dev": true,
+          "requires": {
+            "prelude-ls": "^1.2.1",
+            "type-check": "~0.4.0"
+          }
+        },
+        "optionator": {
+          "version": "0.9.1",
+          "resolved": "https://registry.npmjs.org/optionator/-/optionator-0.9.1.tgz",
+          "integrity": "sha512-74RlY5FCnhq4jRxVUPKDaRwrVNXMqsGsiW6AJw4XK8hmtm10wC0ypZBLw5IIp85NZMr91+qd1RvvENwg7jjRFw==",
+          "dev": true,
+          "requires": {
+            "deep-is": "^0.1.3",
+            "fast-levenshtein": "^2.0.6",
+            "levn": "^0.4.1",
+            "prelude-ls": "^1.2.1",
+            "type-check": "^0.4.0",
+            "word-wrap": "^1.2.3"
+          }
+        },
+        "path-key": {
+          "version": "3.1.1",
+          "resolved": "https://registry.npmjs.org/path-key/-/path-key-3.1.1.tgz",
+          "integrity": "sha512-ojmeN0qd+y0jszEtoY48r0Peq5dwMEkIlCOu6Q5f41lfkswXuKtYrhgoTpLnyIcHm24Uhqx+5Tqm2InSwLhE6Q==",
+          "dev": true
+        },
+        "prelude-ls": {
+          "version": "1.2.1",
+          "resolved": "https://registry.npmjs.org/prelude-ls/-/prelude-ls-1.2.1.tgz",
+          "integrity": "sha512-vkcDPrRZo1QZLbn5RLGPpg/WmIQ65qoWWhcGKf/b5eplkkarX0m9z8ppCat4mlOqUsWpyNuYgO3VRyrYHSzX5g==",
+          "dev": true
+        },
         "regexpp": {
-          "version": "2.0.1",
-          "resolved": "https://registry.npmjs.org/regexpp/-/regexpp-2.0.1.tgz",
-          "integrity": "sha512-lv0M6+TkDVniA3aD1Eg0DVpfU/booSu7Eev3TDO/mZKHBfVjgCGTV4t4buppESEYDtkArYFOxTJWv6S5C+iaNw==",
+          "version": "3.1.0",
+          "resolved": "https://registry.npmjs.org/regexpp/-/regexpp-3.1.0.tgz",
+          "integrity": "sha512-ZOIzd8yVsQQA7j8GCSlPGXwg5PfmA1mrq0JP4nGhh54LaKN3xdai/vHUDu74pKwV8OxseMS65u2NImosQcSD0Q==",
           "dev": true
         },
         "semver": {
-          "version": "5.7.1",
-          "resolved": "https://registry.npmjs.org/semver/-/semver-5.7.1.tgz",
-          "integrity": "sha512-sauaDf/PZdVgrLTNYHRtpXa1iRiKcaebiKQ1BJdpQlWH2lCvexQdX55snPFyK7QzpudqbCI0qXFfOasHdyNDGQ==",
+          "version": "7.3.2",
+          "resolved": "https://registry.npmjs.org/semver/-/semver-7.3.2.tgz",
+          "integrity": "sha512-OrOb32TeeambH6UrhtShmF7CRDqhL6/5XpPNp2DuRH6+9QLw/orhp72j87v8Qa1ScDkvrrBNpZcDejAirJmfXQ==",
           "dev": true
+        },
+        "shebang-command": {
+          "version": "2.0.0",
+          "resolved": "https://registry.npmjs.org/shebang-command/-/shebang-command-2.0.0.tgz",
+          "integrity": "sha512-kHxr2zZpYtdmrN1qDjrrX/Z1rR1kG8Dx+gkpK1G4eXmvXswmcE1hTWBWYUzlraYw1/yZp6YuDY77YtvbN0dmDA==",
+          "dev": true,
+          "requires": {
+            "shebang-regex": "^3.0.0"
+          }
+        },
+        "shebang-regex": {
+          "version": "3.0.0",
+          "resolved": "https://registry.npmjs.org/shebang-regex/-/shebang-regex-3.0.0.tgz",
+          "integrity": "sha512-7++dFhtcx3353uBaq8DDR4NuxBetBzC7ZQOhmTQInHEd6bSrXdiEyzCvG07Z44UYdLShWUyXt5M/yhz8ekcb1A==",
+          "dev": true
+        },
+        "strip-ansi": {
+          "version": "6.0.0",
+          "resolved": "https://registry.npmjs.org/strip-ansi/-/strip-ansi-6.0.0.tgz",
+          "integrity": "sha512-AuvKTrTfQNYNIctbR1K/YGTR1756GycPsg7b9bdV9Duqur4gv6aKqHXah67Z8ImS7WEz5QVcOtlfW2rZEugt6w==",
+          "dev": true,
+          "requires": {
+            "ansi-regex": "^5.0.0"
+          }
+        },
+        "supports-color": {
+          "version": "7.1.0",
+          "resolved": "https://registry.npmjs.org/supports-color/-/supports-color-7.1.0.tgz",
+          "integrity": "sha512-oRSIpR8pxT1Wr2FquTNnGet79b3BWljqOuoW/h4oBhxJ/HUbX5nX6JSruTkvXDCFMwDPvsaTTbvMLKZWSy0R5g==",
+          "dev": true,
+          "requires": {
+            "has-flag": "^4.0.0"
+          }
+        },
+        "type-check": {
+          "version": "0.4.0",
+          "resolved": "https://registry.npmjs.org/type-check/-/type-check-0.4.0.tgz",
+          "integrity": "sha512-XleUoc9uwGXqjWwXaUTZAmzMcFZ5858QA2vvx1Ur5xIcixXIP+8LnFDgRplU30us6teqdlskFfu+ae4K79Ooew==",
+          "dev": true,
+          "requires": {
+            "prelude-ls": "^1.2.1"
+          }
+        },
+        "which": {
+          "version": "2.0.2",
+          "resolved": "https://registry.npmjs.org/which/-/which-2.0.2.tgz",
+          "integrity": "sha512-BLI3Tl1TW3Pvl70l3yq3Y64i+awpwXqsGBYWkkqMtnbXgrMD+yj7rhW0kuEDxzJaYXGjEW5ogapKNMEKNMjibA==",
+          "dev": true,
+          "requires": {
+            "isexe": "^2.0.0"
+          }
         }
       }
     },
@@ -5927,9 +6077,9 @@
       "dev": true
     },
     "eslint-scope": {
-      "version": "5.0.0",
-      "resolved": "https://registry.npmjs.org/eslint-scope/-/eslint-scope-5.0.0.tgz",
-      "integrity": "sha512-oYrhJW7S0bxAFDvWqzvMPRm6pcgcnWc4QnofCAqRTRfQC0JcwenzGglTtsLyIuuWFfkqDG9vz67cnttSd53djw==",
+      "version": "5.1.0",
+      "resolved": "https://registry.npmjs.org/eslint-scope/-/eslint-scope-5.1.0.tgz",
+      "integrity": "sha512-iiGRvtxWqgtx5m8EyQUJihBloE4EnYeGE/bz1wSPwJE6tZuJUtHlhqDM4Xj2ukE8Dyy1+HCZ4hE0fzIVMzb58w==",
       "dev": true,
       "requires": {
         "esrecurse": "^4.1.0",
@@ -5937,9 +6087,9 @@
       }
     },
     "eslint-utils": {
-      "version": "2.0.0",
-      "resolved": "https://registry.npmjs.org/eslint-utils/-/eslint-utils-2.0.0.tgz",
-      "integrity": "sha512-0HCPuJv+7Wv1bACm8y5/ECVfYdfsAm9xmVb7saeFlxjPYALefjhbYoCkBjPdPzGH8wWyTpAez82Fh3VKYEZ8OA==",
+      "version": "2.1.0",
+      "resolved": "https://registry.npmjs.org/eslint-utils/-/eslint-utils-2.1.0.tgz",
+      "integrity": "sha512-w94dQYoauyvlDc43XnGB8lU3Zt713vNChgt4EWwhXAP2XkBvndfxF0AgIqKOOasjPIPzj9JqgwkwbCYD0/V3Zg==",
       "dev": true,
       "requires": {
         "eslint-visitor-keys": "^1.1.0"
@@ -5952,14 +6102,22 @@
       "dev": true
     },
     "espree": {
-      "version": "5.0.1",
-      "resolved": "https://registry.npmjs.org/espree/-/espree-5.0.1.tgz",
-      "integrity": "sha512-qWAZcWh4XE/RwzLJejfcofscgMc9CamR6Tn1+XRXNzrvUSSbiAjGOI/fggztjIi7y9VLPqnICMIPiGyr8JaZ0A==",
+      "version": "7.1.0",
+      "resolved": "https://registry.npmjs.org/espree/-/espree-7.1.0.tgz",
+      "integrity": "sha512-dcorZSyfmm4WTuTnE5Y7MEN1DyoPYy1ZR783QW1FJoenn7RailyWFsq/UL6ZAAA7uXurN9FIpYyUs3OfiIW+Qw==",
       "dev": true,
       "requires": {
-        "acorn": "^6.0.7",
-        "acorn-jsx": "^5.0.0",
-        "eslint-visitor-keys": "^1.0.0"
+        "acorn": "^7.2.0",
+        "acorn-jsx": "^5.2.0",
+        "eslint-visitor-keys": "^1.2.0"
+      },
+      "dependencies": {
+        "eslint-visitor-keys": {
+          "version": "1.3.0",
+          "resolved": "https://registry.npmjs.org/eslint-visitor-keys/-/eslint-visitor-keys-1.3.0.tgz",
+          "integrity": "sha512-6J72N8UNa462wa/KFODt/PJ3IU60SDpC3QXC1Hjc1BXXpfL2C9R5+AU7jhe0F6GREqVMh4Juu+NY7xn+6dipUQ==",
+          "dev": true
+        }
       }
     },
     "esprima": {
@@ -6486,6 +6644,15 @@
         "path-is-absolute": "^1.0.0"
       }
     },
+    "glob-parent": {
+      "version": "5.1.1",
+      "resolved": "https://registry.npmjs.org/glob-parent/-/glob-parent-5.1.1.tgz",
+      "integrity": "sha512-FnI+VGOpnlGHWZxthPGR+QhR78fuiK0sNLkHQv+bL9fQi57lNNdquIbna/WrfROrolq8GK5Ek6BiMwqL/voRYQ==",
+      "dev": true,
+      "requires": {
+        "is-glob": "^4.0.1"
+      }
+    },
     "globals": {
       "version": "11.12.0",
       "resolved": "https://registry.npmjs.org/globals/-/globals-11.12.0.tgz",
@@ -12781,12 +12948,6 @@
       "integrity": "sha1-F0uSaHNVNP+8es5r9TpanhtcX18=",
       "dev": true
     },
-    "path-is-inside": {
-      "version": "1.0.2",
-      "resolved": "https://registry.npmjs.org/path-is-inside/-/path-is-inside-1.0.2.tgz",
-      "integrity": "sha1-NlQX3t5EQw0cEa9hAn+s8HS9/FM=",
-      "dev": true
-    },
     "path-key": {
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/path-key/-/path-key-2.0.1.tgz",
@@ -13862,9 +14023,9 @@
       "dev": true
     },
     "strip-json-comments": {
-      "version": "2.0.1",
-      "resolved": "https://registry.npmjs.org/strip-json-comments/-/strip-json-comments-2.0.1.tgz",
-      "integrity": "sha1-PFMZQukIwml8DsNEhYwobHygpgo=",
+      "version": "3.1.0",
+      "resolved": "https://registry.npmjs.org/strip-json-comments/-/strip-json-comments-3.1.0.tgz",
+      "integrity": "sha512-e6/d0eBu7gHtdCqFt0xJr642LdToM5/cN4Qb9DbHjVx1CP5RyeM+zH7pbecEmDv/lBqb0QH+6Uqq75rxFPkM0w==",
       "dev": true
     },
     "supports-color": {
@@ -14317,6 +14478,12 @@
       "dev": true,
       "optional": true
     },
+    "v8-compile-cache": {
+      "version": "2.1.1",
+      "resolved": "https://registry.npmjs.org/v8-compile-cache/-/v8-compile-cache-2.1.1.tgz",
+      "integrity": "sha512-8OQ9CL+VWyt3JStj7HX7/ciTL2V3Rl1Wf5OL+SNTm0yK1KvtReVulksyeRnCANHHuUxHlQig+JJDlUhBt1NQDQ==",
+      "dev": true
+    },
     "v8-to-istanbul": {
       "version": "4.1.4",
       "resolved": "https://registry.npmjs.org/v8-to-istanbul/-/v8-to-istanbul-4.1.4.tgz",

package.json

@@ -1,8 +1,8 @@
 {
-  "name": "pr-changed-files-filter",
+  "name": "paths-filter",
   "version": "1.0.0",
   "private": true,
-  "description": "Enables conditional execution of workflow job steps considering which files are modified by a pull request.",
+  "description": "Execute your workflow steps only if relevant files are modified.",
   "main": "lib/main.js",
   "scripts": {
     "build": "tsc",
@@ -36,9 +36,9 @@
     "@types/js-yaml": "^3.12.4",
     "@types/minimatch": "^3.0.3",
     "@types/node": "^14.0.5",
-    "@typescript-eslint/parser": "^3.0.0",
+    "@typescript-eslint/parser": "^3.3.0",
     "@zeit/ncc": "^0.22.3",
-    "eslint": "^5.16.0",
+    "eslint": "^7.3.0",
     "eslint-plugin-github": "^2.0.0",
     "eslint-plugin-jest": "^22.21.0",
     "jest": "^26.0.1",

src/filter.ts

@@ -15,10 +15,11 @@ export default class Filter {
     }
 
     for (const name of Object.keys(doc)) {
-      const patterns = doc[name] as string[]
-      if (!Array.isArray(patterns)) {
+      const patternsNode = doc[name]
+      if (!Array.isArray(patternsNode)) {
         this.throwInvalidFormatError()
       }
+      const patterns = flat(patternsNode) as string[]
       if (!patterns.every(x => typeof x === 'string')) {
         this.throwInvalidFormatError()
       }
@@ -40,3 +41,9 @@ export default class Filter {
     throw new Error('Invalid filter YAML format: Expected dictionary of string arrays')
   }
 }
+
+// Creates a new array with all sub-array elements recursively concatenated
+// In future could be replaced by Array.prototype.flat (supported on Node.js 11+)
+function flat(arr: any[]): any[] {
+  return arr.reduce((acc, val) => acc.concat(Array.isArray(val) ? flat(val) : val), [])
+}

src/git.ts

@@ -1,22 +1,25 @@
 import {exec} from '@actions/exec'
 
-export async function fetchBranch(base: string): Promise<void> {
-  const exitCode = await exec('git', ['fetch', '--depth=1', 'origin', base])
+export const NULL_SHA = '0000000000000000000000000000000000000000'
+export const FETCH_HEAD = 'FETCH_HEAD'
+
+export async function fetchCommit(ref: string): Promise<void> {
+  const exitCode = await exec('git', ['fetch', '--depth=1', '--no-tags', 'origin', ref])
   if (exitCode !== 0) {
-    throw new Error(`Fetching branch ${base} failed, exiting`)
+    throw new Error(`Fetching ${ref} failed`)
   }
 }
 
-export async function getChangedFiles(base: string): Promise<string[]> {
+export async function getChangedFiles(ref: string): Promise<string[]> {
   let output = ''
-  const exitCode = await exec('git', ['diff-index', '--name-only', base], {
+  const exitCode = await exec('git', ['diff-index', '--name-only', ref], {
     listeners: {
       stdout: (data: Buffer) => (output += data.toString())
     }
   })
 
   if (exitCode !== 0) {
-    throw new Error(`Couldn't determine changed files, exiting`)
+    throw new Error(`Couldn't determine changed files`)
   }
 
   return output
@@ -24,3 +27,20 @@ export async function getChangedFiles(base: string): Promise<string[]> {
     .map(s => s.trim())
     .filter(s => s.length > 0)
 }
+
+export function isTagRef(ref: string): boolean {
+  return ref.startsWith('refs/tags/')
+}
+
+export function trimRefs(ref: string): string {
+  return trimStart(ref, 'refs/')
+}
+
+export function trimRefsHeads(ref: string): string {
+  const trimRef = trimStart(ref, 'refs/')
+  return trimStart(trimRef, 'heads/')
+}
+
+function trimStart(ref: string, start: string): string {
+  return ref.startsWith(start) ? ref.substr(start.length) : ref
+}

src/main.ts

@@ -12,18 +12,20 @@ async function run(): Promise<void> {
     const filtersInput = core.getInput('filters', {required: true})
     const filtersYaml = isPathInput(filtersInput) ? getConfigFileContent(filtersInput) : filtersInput
 
-    if (github.context.eventName !== 'pull_request') {
-      core.setFailed('This action can be triggered only by pull_request event')
-      return
-    }
-
-    const pr = github.context.payload.pull_request as Webhooks.WebhookPayloadPullRequestPullRequest
     const filter = new Filter(filtersYaml)
-    const files = token ? await getChangedFilesFromApi(token, pr) : await getChangedFilesFromGit(pr)
+    const files = await getChangedFiles(token)
 
-    const result = filter.match(files)
-    for (const key in result) {
-      core.setOutput(key, String(result[key]))
+    if (files === null) {
+      // Change detection was not possible
+      // Set all filter keys to true (i.e. changed)
+      for (const key in filter.rules) {
+        core.setOutput(key, String(true))
+      }
+    } else {
+      const result = filter.match(files)
+      for (const key in result) {
+        core.setOutput(key, String(result[key]))
+      }
     }
   } catch (error) {
     core.setFailed(error.message)
@@ -46,12 +48,45 @@ function getConfigFileContent(configPath: string): string {
   return fs.readFileSync(configPath, {encoding: 'utf8'})
 }
 
+async function getChangedFiles(token: string): Promise<string[] | null> {
+  if (github.context.eventName === 'pull_request') {
+    const pr = github.context.payload.pull_request as Webhooks.WebhookPayloadPullRequestPullRequest
+    return token ? await getChangedFilesFromApi(token, pr) : await getChangedFilesFromGit(pr.base.sha)
+  } else if (github.context.eventName === 'push') {
+    return getChangedFilesFromPush()
+  } else {
+    throw new Error('This action can be triggered only by pull_request or push event')
+  }
+}
+
+async function getChangedFilesFromPush(): Promise<string[] | null> {
+  const push = github.context.payload as Webhooks.WebhookPayloadPush
+
+  // No change detection for pushed tags
+  if (git.isTagRef(push.ref)) return null
+
+  // Get base from input or use repo default branch.
+  // It it starts with 'refs/', it will be trimmed (git fetch refs/heads/<NAME> doesn't work)
+  const baseInput = git.trimRefs(core.getInput('base', {required: false}) || push.repository.default_branch)
+
+  // If base references same branch it was pushed to, we will do comparison against the previously pushed commit.
+  // Otherwise changes are detected against the base reference
+  const base = git.trimRefsHeads(baseInput) === git.trimRefsHeads(push.ref) ? push.before : baseInput
+
+  // There is no previous commit for comparison
+  // e.g. change detection against previous commit of just pushed new branch
+  if (base === git.NULL_SHA) return null
+
+  return await getChangedFilesFromGit(base)
+}
+
 // Fetch base branch and use `git diff` to determine changed files
-async function getChangedFilesFromGit(pullRequest: Webhooks.WebhookPayloadPullRequestPullRequest): Promise<string[]> {
+async function getChangedFilesFromGit(ref: string): Promise<string[]> {
   core.debug('Fetching base branch and using `git diff-index` to determine changed files')
-  const baseRef = pullRequest.base.ref
-  await git.fetchBranch(baseRef)
-  return await git.getChangedFiles(pullRequest.base.sha)
+  await git.fetchCommit(ref)
+  // FETCH_HEAD will always point to the just fetched commit
+  // No matter if ref is SHA, branch or tag name or full git ref
+  return await git.getChangedFiles(git.FETCH_HEAD)
 }
 
 // Uses github REST api to get list of files changed in PR