fix(ci): Fix command substitution in update flake.lock CI job

Author: mrjones2014

.github/workflows/update-flake-dependencies.yml

@@ -1,27 +1,25 @@
 # CI job to periodically (once a week) update flake.lock
 name: Update flake dependencies
-
 on:
   schedule:
     - cron: '0 16 * * 5'
   workflow_dispatch: # for allowing manual triggers of the workflow
-
 jobs:
   update-dependencies:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
-    - uses: DeterminateSystems/nix-installer-action@main
-    - uses: DeterminateSystems/magic-nix-cache-action@main
-    - name: update flake.lock
-      run: nix flake update
-    - name: Create signed commit with flake.lock changes
-      env:
-        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        FILE_TO_COMMIT: flake.lock
-        COMMIT_BRANCH: automation/update-flake-dependencies
-        COMMIT_MESSAGE: "chore(nix): Update Flake dependencies"
-      run: |
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: DeterminateSystems/magic-nix-cache-action@main
+      - name: update flake.lock
+        run: nix flake update
+      - name: Create signed commit with flake.lock changes
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          FILE_TO_COMMIT: flake.lock
+          COMMIT_BRANCH: automation/update-flake-dependencies
+          COMMIT_MESSAGE: "chore(nix): Update Flake dependencies"
+        run: |
           # make sure something actually changed first, if not, no updates required
           if [[ `git status --porcelain` ]]; then
             # create the branch on the remote
@@ -30,7 +28,7 @@ jobs:
             # commit via the GitHub API so we get automatic commit signing
             gh api --method PUT /repos/1Password/shell-plugins/contents/$FILE_TO_COMMIT \
               --field message="$COMMIT_MESSAGE" \
-              --field content=@<(base64 -i $FILE_TO_COMMIT) \
+              --field content="$(base64 -w 0 $FILE_TO_COMMIT)" \
               --field branch="$COMMIT_BRANCH" \
               --field sha="$(git rev-parse $COMMIT_BRANCH:$FILE_TO_COMMIT)"
             gh pr create --title "[automation]: Update Flake dependencies" \