fix: error detecting initial commits

src/commitSha.ts

@@ -63,6 +63,7 @@ export interface DiffResult {
   currentBranch: string
   targetBranch: string
   diff: string
+  initialCommit?: boolean
 }
 
 export const getSHAForPushEvent = async (
@@ -201,20 +202,15 @@ export const getSHAForPushEvent = async (
         })
       }
 
-      if (previousSha === currentSha) {
-        if (!(await getParentSha({cwd: workingDirectory}))) {
+      if (!previousSha || previousSha === currentSha) {
+        previousSha = await getParentSha({
+          cwd: workingDirectory
+        })
+
+        if (!previousSha) {
           core.warning('Initial commit detected no previous commit found.')
           initialCommit = true
           previousSha = currentSha
-        } else {
-          previousSha = await getParentSha({
-            cwd: workingDirectory
-          })
-        }
-      } else {
-        if (!previousSha) {
-          core.error('Unable to locate a previous commit.')
-          throw new Error('Unable to locate a previous commit.')
         }
       }
     }
@@ -241,7 +237,8 @@ export const getSHAForPushEvent = async (
     currentSha,
     currentBranch,
     targetBranch,
-    diff
+    diff,
+    initialCommit
   }
 }
 

src/main.ts

@@ -89,6 +89,12 @@ export async function run(): Promise<void> {
     )
   }
 
+  if (diffResult.initialCommit) {
+    core.info('This is the first commit for this repository; exiting...')
+    core.endGroup()
+    return
+  }
+
   core.info(
     `Retrieving changes between ${diffResult.previousSha} (${diffResult.targetBranch}) → ${diffResult.currentSha} (${diffResult.currentBranch})`
   )

src/utils.ts

@@ -526,15 +526,20 @@ export const gitLsRemote = async ({
 }
 
 export const getParentSha = async ({cwd}: {cwd: string}): Promise<string> => {
-  const {stdout} = await exec.getExecOutput(
+  const {stdout, exitCode} = await exec.getExecOutput(
     'git',
     ['rev-list', '-n', '1', 'HEAD^'],
     {
       cwd,
+      ignoreReturnCode: true,
       silent: process.env.RUNNER_DEBUG !== '1'
     }
   )
 
+  if (exitCode !== 0) {
+    return ''
+  }
+
   return stdout.trim()
 }