fix: reset author and sign during backport (#1069)

(cherry picked from commit 6cd2915)

# Conflicts:
#	.backportrc.json

Author: lleyton

.backportrc.json

@@ -0,0 +1,9 @@
+{
+  "repoOwner": "terrapkg",
+  "repoName": "packages",
+  "resetAuthor": true,
+  "targetBranchChoices": ["f38", "f39", "f40", "frawhide"],
+  "branchLabelMapping": {
+    "^sync-(.+)$": "$1"
+  }
+}

.github/workflows/sync.yml

@@ -9,6 +9,18 @@ jobs:
     name: Backport/sync PR
     runs-on: ubuntu-latest
     steps:
+      - name: Install SSH signing key
+        run: |
+          mkdir -p ${{ runner.temp }}
+          echo "${{ secrets.SSH_SIGNING_KEY }}" > ${{ runner.temp }}/signing_key
+          chmod 0700 ${{ runner.temp }}/signing_key
+
+      - name: Setup Raboneko Signing
+        run: |
+          git config --global gpg.format "ssh"
+          git config --global user.signingkey "${{ runner.temp }}/signing_key"
+          git config --global commit.gpgsign true
+
       - name: Backport Action
         uses: sorenlouv/[email protected]
         with: