add our feature

src/git-source-provider.ts

@@ -130,6 +130,21 @@ export async function getSource(settings: IGitSourceSettings): Promise<void> {
     await authHelper.configureAuth()
     core.endGroup()
 
+    if (settings.defaultRefOnError && settings.defaultRefOnError === true) {
+      // Configure default branch
+      core.startGroup('Setting up default branch')
+      if (settings.sshKey) {
+        settings.defaultBranch = await git.getDefaultBranch(repositoryUrl)
+      } else {
+        settings.defaultBranch = await githubApiHelper.getDefaultBranch(
+          settings.authToken,
+          settings.repositoryOwner,
+          settings.repositoryName
+        )
+      }
+      core.endGroup()
+    }
+
     // Determine the default branch
     if (!settings.ref && !settings.commit) {
       core.startGroup('Determining the default branch')
@@ -166,7 +181,10 @@ export async function getSource(settings: IGitSourceSettings): Promise<void> {
       fetchOptions.filter = 'blob:none'
     }
 
-    if (settings.fetchDepth <= 0) {
+    if (
+      settings.fetchDepth <= 0 ||
+      (settings.defaultRefOnError && settings.defaultRefOnError === true)
+    ) {
       // Fetch all branches and tags
       let refSpec = refHelper.getRefSpecForAllHistory(
         settings.ref,
@@ -190,11 +208,31 @@ export async function getSource(settings: IGitSourceSettings): Promise<void> {
 
     // Checkout info
     core.startGroup('Determining the checkout info')
-    const checkoutInfo = await refHelper.getCheckoutInfo(
-      git,
-      settings.ref,
-      settings.commit
-    )
+    let checkoutInfo: refHelper.ICheckoutInfo
+    if (settings.defaultRefOnError && settings.defaultRefOnError === true) {
+      try {
+        checkoutInfo = await refHelper.getCheckoutInfo(
+          git,
+          settings.ref,
+          settings.commit
+        )
+      } catch (error) {
+        core.info(
+          'Could not determine the checkout info. Trying the default repo branch'
+        )
+        checkoutInfo = await refHelper.getCheckoutInfo(
+          git,
+          settings.defaultBranch,
+          settings.commit
+        )
+      }
+    } else {
+      checkoutInfo = await refHelper.getCheckoutInfo(
+        git,
+        settings.ref,
+        settings.commit
+      )
+    }
     core.endGroup()
 
     // LFS fetch

src/git-source-settings.ts

@@ -19,6 +19,16 @@ export interface IGitSourceSettings {
    */
   ref: string
 
+  /**
+   * Whether to checkout the default repository branch if specified ref does not exist.
+   */
+  defaultRefOnError: boolean
+
+  /**
+   * The target ref to fetch if it exists
+   */
+  defaultBranch: string
+
   /**
    * The commit to checkout
    */

src/input-helper.ts

@@ -78,6 +78,11 @@ export async function getInputs(): Promise<IGitSourceSettings> {
   core.debug(`ref = '${result.ref}'`)
   core.debug(`commit = '${result.commit}'`)
 
+  // Default ref on error
+  result.defaultRefOnError =
+    (core.getInput('default-ref-on-error') || 'true').toUpperCase() === 'TRUE'
+  core.debug(`default-ref-on-error = '${result.defaultRefOnError}'`)
+
   // Clean
   result.clean = (core.getInput('clean') || 'true').toUpperCase() === 'TRUE'
   core.debug(`clean = ${result.clean}`)