Update Sigstore Timestamp using dependabot

.github/dependabot.yml

@@ -27,3 +27,14 @@ updates:
       actions:
         patterns:
           - "*"
+
+  - package-ecosystem: gomod
+    directory: "/.github"
+    schedule:
+      interval: daily
+    open-pull-requests-limit: 1
+    rebase-strategy: "disabled"
+    groups:
+      actions:
+        patterns:
+          - "*"

.github/go.mod

@@ -0,0 +1,11 @@
+module sigstore/sigstore-python
+
+go 1.23
+
+require (
+    // We don't have a Go module here but this file is picked up by dependabot
+    // and this will automatically update the dependency when needed.
+
+    github.com/sigstore/timestamp-authority v1.2.3
+
+)

.github/workflows/ci.yml

@@ -61,7 +61,8 @@ jobs:
       - name: test (timestamp-authority)
         if: ${{ matrix.conf.os == 'ubuntu-latest' }}
         run: |
-          wget https://github.com/sigstore/timestamp-authority/releases/download/${SIGSTORE_TIMESTAMP}/timestamp-server-linux-amd64 -O /tmp/timestamp-server
+          SIGSTORE_TIMESTAMP_VERSION=$(grep "github.com/sigstore/timestamp-authority" .github/go.mod | awk '{print $2}')
+          wget https://github.com/sigstore/timestamp-authority/releases/download/${SIGSTORE_TIMESTAMP_VERSION}/timestamp-server-linux-amd64 -O /tmp/timestamp-server
           chmod +x /tmp/timestamp-server
           # Run the TSA in background
           /tmp/timestamp-server serve --port 3000 --disable-ntp-monitoring &
@@ -70,8 +71,6 @@ jobs:
           # having pytest show skipped tests and verifying ours are running
           make test TEST_ARGS="-m timestamp_authority -rs" | tee output
           ! grep -q "skipping test that requires a Timestamp Authority" output || (echo "ERROR: Found skip message" && exit 1)
-        env:
-          SIGSTORE_TIMESTAMP: "v1.2.3"
 
       - name: test (interactive)
         if: (github.event_name != 'pull_request') || !github.event.pull_request.head.repo.fork