diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 5b639c4569c..8b9c37d688b 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -4,11 +4,28 @@ on:
   push:
     branches:
       - main
+      - '**'
   pull_request:
     branches:
       - main
 
 jobs:
+  test-no-head-sha:
+    runs-on: ubuntu-latest
+    name: Test changed-files missing head sha
+    steps:
+      - name: Checkout to branch
+        uses: actions/checkout@v2
+      
+      - name: Run changed-files with defaults
+        id: changed-files
+        continue-on-error: true
+        uses: ./
+      
+      - name: Show output
+        run: |
+          echo "${{ toJSON(steps.changed-files.outputs) }}"
+
   test:
     runs-on: ubuntu-latest
     name: Test changed-files
diff --git a/entrypoint.sh b/entrypoint.sh
index 161a3817ca8..6789ecf6587 100644
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -7,90 +7,92 @@ git remote set-url origin "https://${INPUT_TOKEN}@github.com/${GITHUB_REPOSITORY
 echo "Getting head sha..."
 
 if [[ -z $GITHUB_BASE_REF ]]; then
-  HEAD_SHA=$(git rev-parse HEAD^1 || true)
+  HEAD_SHA=$(git rev-parse HEAD^1 2>&1) && exit_status=$? || exit_status=$?
 else
   TARGET_BRANCH=${GITHUB_BASE_REF}
   git fetch --depth=1 origin "${TARGET_BRANCH}":"${TARGET_BRANCH}"
-  HEAD_SHA=$(git rev-parse "${TARGET_BRANCH}" || true)
+  HEAD_SHA=$(git rev-parse "${TARGET_BRANCH}" 2>&1) && exit_status=$? || exit_status=$?
 fi
 
-if [[ -z $HEAD_SHA ]]; then
-  echo "::warning::Unable to determine the head sha: $HEAD_SHA."
+if [[ $exit_status -ne 0 ]]; then
+  echo "::warning::Unable to determine the head sha"
   echo "::warning::You seem to be missing 'fetch-depth: 0' or 'fetch-depth: 2'"
   exit 1
+fi
+
+echo "Using head sha: $HEAD_SHA..."
+
+if [[ -z "$INPUT_FILES" ]]; then
+  echo "Getting diff..."
+  ADDED=$(git diff --diff-filter=A --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  COPIED=$(git diff --diff-filter=C --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  DELETED=$(git diff --diff-filter=D --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  MODIFIED=$(git diff --diff-filter=M --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  RENAMED=$(git diff --diff-filter=R --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  CHANGED=$(git diff --diff-filter=T --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  UNMERGED=$(git diff --diff-filter=U --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  UNKNOWN=$(git diff --diff-filter=X --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  ALL_CHANGED=$(git diff --diff-filter="*ACDMRTUX" --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
+  ALL_MODIFIED_FILES=$(git diff --diff-filter="ACM" --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
 else
-  echo "Using head sha: $HEAD_SHA..."
-  if [[ -z "$INPUT_FILES" ]]; then
-    echo "Getting diff..."
-    ADDED=$(git diff --diff-filter=A --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-    COPIED=$(git diff --diff-filter=C --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-    DELETED=$(git diff --diff-filter=D --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-    MODIFIED=$(git diff --diff-filter=M --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-    RENAMED=$(git diff --diff-filter=R --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-    CHANGED=$(git diff --diff-filter=T --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-    UNMERGED=$(git diff --diff-filter=U --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-    UNKNOWN=$(git diff --diff-filter=X --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-    ALL_CHANGED=$(git diff --diff-filter="*ACDMRTUX" --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-    ALL_MODIFIED_FILES=$(git diff --diff-filter="ACM" --name-only "$HEAD_SHA" | tr "\n" "$INPUT_SEPARATOR" | sed -E "s/($INPUT_SEPARATOR)$//")
-  else
-    ADDED_ARRAY=()
-    COPIED_ARRAY=()
-    DELETED_ARRAY=()
-    MODIFIED_ARRAY=()
-    RENAMED_ARRAY=()
-    CHANGED_ARRAY=()
-    UNMERGED_ARRAY=()
-    UNKNOWN_ARRAY=()
-    ALL_CHANGED_ARRAY=()
-    ALL_MODIFIED_FILES_ARRAY=()
-    for path in ${INPUT_FILES}
-    do
-      echo "Checking for file changes: \"${path}\"..."
-      IFS=" "
-      # shellcheck disable=SC2207
-      ADDED_ARRAY+=($(git diff --diff-filter=A --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
-      # shellcheck disable=SC2207
-      COPIED_ARRAY+=($(git diff --diff-filter=C --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
-      # shellcheck disable=SC2207
-      DELETED_ARRAY+=($(git diff --diff-filter=D --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
-      # shellcheck disable=SC2207
-      MODIFIED_ARRAY+=($(git diff --diff-filter=M --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
-      # shellcheck disable=SC2207
-      RENAMED_ARRAY+=($(git diff --diff-filter=R --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
-      # shellcheck disable=SC2207
-      CHANGED_ARRAY+=($(git diff --diff-filter=T --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
-      # shellcheck disable=SC2207
-      UNMERGED_ARRAY+=($(git diff --diff-filter=U --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
-      # shellcheck disable=SC2207
-      UNKNOWN_ARRAY+=($(git diff --diff-filter=X --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
-      # shellcheck disable=SC2207
-      ALL_CHANGED_ARRAY+=($(git diff --diff-filter="*ACDMRTUX" --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
-      # shellcheck disable=SC2207
-      ALL_MODIFIED_FILES_ARRAY+=($(git diff --diff-filter="ACM" --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
-    done
+  ADDED_ARRAY=()
+  COPIED_ARRAY=()
+  DELETED_ARRAY=()
+  MODIFIED_ARRAY=()
+  RENAMED_ARRAY=()
+  CHANGED_ARRAY=()
+  UNMERGED_ARRAY=()
+  UNKNOWN_ARRAY=()
+  ALL_CHANGED_ARRAY=()
+  ALL_MODIFIED_FILES_ARRAY=()
+  for path in ${INPUT_FILES}
+  do
+    echo "Checking for file changes: \"${path}\"..."
+    IFS=" "
+    # shellcheck disable=SC2207
+    ADDED_ARRAY+=($(git diff --diff-filter=A --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
+    # shellcheck disable=SC2207
+    COPIED_ARRAY+=($(git diff --diff-filter=C --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
+    # shellcheck disable=SC2207
+    DELETED_ARRAY+=($(git diff --diff-filter=D --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
+    # shellcheck disable=SC2207
+    MODIFIED_ARRAY+=($(git diff --diff-filter=M --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
+    # shellcheck disable=SC2207
+    RENAMED_ARRAY+=($(git diff --diff-filter=R --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
+    # shellcheck disable=SC2207
+    CHANGED_ARRAY+=($(git diff --diff-filter=T --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
+    # shellcheck disable=SC2207
+    UNMERGED_ARRAY+=($(git diff --diff-filter=U --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
+    # shellcheck disable=SC2207
+    UNKNOWN_ARRAY+=($(git diff --diff-filter=X --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
+    # shellcheck disable=SC2207
+    ALL_CHANGED_ARRAY+=($(git diff --diff-filter="*ACDMRTUX" --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
+    # shellcheck disable=SC2207
+    ALL_MODIFIED_FILES_ARRAY+=($(git diff --diff-filter="ACM" --name-only "$HEAD_SHA" | grep -E "(${path})" | xargs || true))
+  done
 
-    # shellcheck disable=SC2001
-    ADDED=$(echo "${ADDED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
-    # shellcheck disable=SC2001
-    COPIED=$(echo "${COPIED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
-    # shellcheck disable=SC2001
-    DELETED=$(echo "${DELETED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
-    # shellcheck disable=SC2001
-    MODIFIED=$(echo "${MODIFIED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
-    # shellcheck disable=SC2001
-    RENAMED=$(echo "${RENAMED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
-    # shellcheck disable=SC2001
-    CHANGED=$(echo "${CHANGED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
-    # shellcheck disable=SC2001
-    UNMERGED=$(echo "${UNMERGED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
-    # shellcheck disable=SC2001
-    UNKNOWN=$(echo "${UNKNOWN_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
-    # shellcheck disable=SC2001
-    ALL_CHANGED=$(echo "${ALL_CHANGED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
-    # shellcheck disable=SC2001
-    ALL_MODIFIED_FILES=$(echo "${ALL_MODIFIED_FILES_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
-  fi
+  # shellcheck disable=SC2001
+  ADDED=$(echo "${ADDED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
+  # shellcheck disable=SC2001
+  COPIED=$(echo "${COPIED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
+  # shellcheck disable=SC2001
+  DELETED=$(echo "${DELETED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
+  # shellcheck disable=SC2001
+  MODIFIED=$(echo "${MODIFIED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
+  # shellcheck disable=SC2001
+  RENAMED=$(echo "${RENAMED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
+  # shellcheck disable=SC2001
+  CHANGED=$(echo "${CHANGED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
+  # shellcheck disable=SC2001
+  UNMERGED=$(echo "${UNMERGED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
+  # shellcheck disable=SC2001
+  UNKNOWN=$(echo "${UNKNOWN_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
+  # shellcheck disable=SC2001
+  ALL_CHANGED=$(echo "${ALL_CHANGED_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
+  # shellcheck disable=SC2001
+  ALL_MODIFIED_FILES=$(echo "${ALL_MODIFIED_FILES_ARRAY[*]}" | sed 's/  */'"$INPUT_SEPARATOR"'/g')
 fi
+
 echo "Added files: $ADDED"
 echo "Copied files: $COPIED"
 echo "Deleted files: $DELETED"