feat: add support to detect changes for merge group event (#1404)

Co-authored-by: GitHub Action <action@github.com>

src/commitSha.ts

@@ -57,6 +57,8 @@ const getCurrentSHA = async ({
         })) === 0
       ) {
         currentSha = github.context.payload.pull_request?.head?.sha
+      } else if (github.context.eventName === 'merge_group') {
+        currentSha = github.context.payload.merge_group?.head_sha
       } else {
         currentSha = await getHeadSha({cwd: workingDirectory})
       }
@@ -78,7 +80,7 @@ export interface DiffResult {
   initialCommit?: boolean
 }
 
-export const getSHAForPushEvent = async (
+export const getSHAForNonPullRequestEvent = async (
   inputs: Inputs,
   env: Env,
   workingDirectory: string,
@@ -197,12 +199,17 @@ export const getSHAForPushEvent = async (
       previousSha = sha
       targetBranch = tag
     } else {
-      core.debug('Getting previous SHA for last remote commit...')
-      if (
-        github.context.payload.forced === 'false' ||
-        !github.context.payload.forced
-      ) {
-        previousSha = github.context.payload.before
+      if (github.context.eventName === 'merge_group') {
+        core.debug('Getting previous SHA for merge group...')
+        previousSha = github.context.payload.merge_group?.base_sha
+      } else {
+        core.debug('Getting previous SHA for last remote commit...')
+        if (
+          github.context.payload.forced === 'false' ||
+          !github.context.payload.forced
+        ) {
+          previousSha = github.context.payload.before
+        }
       }
 
       if (

src/main.ts

@@ -12,7 +12,7 @@ import {setChangedFilesOutput} from './changedFilesOutput'
 import {
   DiffResult,
   getSHAForPullRequestEvent,
-  getSHAForPushEvent
+  getSHAForNonPullRequestEvent
 } from './commitSha'
 import {Env, getEnv} from './env'
 import {getInputs, Inputs} from './inputs'
@@ -130,7 +130,7 @@ const getChangedFilesFromLocalGit = async ({
 
   if (!github.context.payload.pull_request?.base?.ref) {
     core.info(`Running on a ${github.context.eventName || 'push'} event...`)
-    diffResult = await getSHAForPushEvent(
+    diffResult = await getSHAForNonPullRequestEvent(
       inputs,
       env,
       workingDirectory,