Use reuseable action for flake update actions (#42)

Reviewed-on: https://codeberg.org/tmayoff/.dotfiles/pulls/42
Co-authored-by: Tyler Mayoff <tyler@tylermayoff.com>
Co-committed-by: Tyler Mayoff <tyler@tylermayoff.com>

.forgejo/actions/flake-update/action.yml

@@ -0,0 +1,54 @@
+name: "Flake lock updater"
+description: "Updates the flake lock file"
+inputs:
+  flake_path:
+    description: "Relative path to the flake.nix file"
+    default: './'
+    required: false
+  token:
+    description: "Authentication token"
+    default: ""
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - name: Update flake.lock
+      id: update
+      shell: bash
+      run: |
+        nix flake update --flake ${{ inputs.flake_path }} 2> >(tee /dev/stderr) | awk '
+          /^• Updated input/ {in_update = 1; print; next}
+          in_update && !/^warning:/ {print}
+          /^$/ {in_update = 0}
+        ' > update.log
+
+        echo "UPDATE_LOG<<EOF" >> $GITHUB_ENV
+        cat update.log >> $GITHUB_ENV 
+        echo "EOF" >> $GITHUB_ENV
+
+        rm update.log
+
+    - name: Create PR
+      shell: bash
+      run: |
+        BRANCH="update-flake-lock"
+
+        git fetch origin
+        git checkout main
+
+        if git show-ref --verify --quiet refs/heads/$BRANCH; then
+          git checkout $BRANCH
+          git reset --hard origin/main
+        else
+          git checkout -b $BRANCH origin/main
+        fi
+
+        git checkout -B update-flake-lock
+        git add ${{ inputs.flake_path }}/flake.lock
+        git config user.name "${{ env.GITHUB_ACTOR }}"
+        git config user.email "tyler@mayoff.ca"
+        git commit -m "updated lockfile"
+        git push origin update-flake-lock
+        nix run nixpkgs#forgejo-cli -- auth add-key ${{ env.GITHUB_ACTOR }} ${{ inputs.token }}
+        nix run nixpkgs#forgejo-cli -- pr create "automated: Update flake.lock" --body "body tests" --head update-flake-lock  || echo "PR may already exist"