scheduled workflows: fix branch, add new files.

- ensure we reset to `origin/master` so we only have the commit we care
  about in the PR
- ensure we `git add` to include any new files
- don't use `git commit -a` and instead rely only on files added with
  `git add`

.github/workflows/spdx.yml

@@ -30,7 +30,9 @@ jobs:
           if brew update-license-data --fail-if-not-changed; then
             if ! git ls-remote --exit-code --heads origin spdx-update; then
               git checkout -B spdx-update
-              git commit -am "spdx: update license data." -m "Autogenerated by [a scheduled GitHub Action](https://github.com/Homebrew/brew/blob/master/.github/workflows/spdx.yml)."
+              git reset origin/master
+              git add data/spdx
+              git commit -m "spdx: update license data." -m "Autogenerated by [a scheduled GitHub Action](https://github.com/Homebrew/brew/blob/master/.github/workflows/spdx.yml)."
               echo "::set-output name=committed::true"
             fi
           fi

.github/workflows/tapioca.yml

@@ -40,9 +40,11 @@ jobs:
           bundle exec srb rbi hidden-definitions
 
           git checkout -B tapioca-update
-          if ! git diff --exit-code -- sorbet; then
+          git reset origin/master
+          git add sorbet
+          if ! git --no-patch --exit-code HEAD -- sorbet; then
             if ! git ls-remote --exit-code --heads origin tapioca-update; then
-              git commit -am "sorbet: update RBI files using Tapioca." -m "Autogenerated by [a scheduled GitHub Action](https://github.com/Homebrew/brew/blob/master/.github/workflows/tapioca.yml)."
+              git commit -m "sorbet: update RBI files using Tapioca." -m "Autogenerated by [a scheduled GitHub Action](https://github.com/Homebrew/brew/blob/master/.github/workflows/tapioca.yml)."
               echo "::set-output name=committed::true"
             fi
           fi