ci: remove dependabot + gomod, always fetch latest (#1293)

* ci: remove dependabot + gomod, always fetch latest

Instead of using Dependabot to test, this always
fetches the latest TSA build.

I'm not positive this is a great idea, however.

Signed-off-by: William Woodruff <william@trailofbits.com>
Co-authored-by: Jussi Kukkonen <jkukkonen@google.com>

Author: woodruffw

.github/dependabot.yml

@@ -27,14 +27,3 @@ 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

@@ -62,19 +62,27 @@ jobs:
       - name: test
         run: make test TEST_ARGS="-vv --showlocals"
 
+      # TODO: Refactor this or remove it entirely once there's
+      # a suitable staging TSA instance.
       - name: test (timestamp-authority)
         if: ${{ matrix.conf.os == 'ubuntu-latest' }}
         run: |
-          SIGSTORE_TIMESTAMP_VERSION=$(grep "github.com/sigstore/timestamp-authority" .github/go.mod | awk '{print $3}')
+          # Fetch the latest sigstore/timestamp-authority build
+          SIGSTORE_TIMESTAMP_VERSION=$(gh api /repos/sigstore/timestamp-authority/tags --jq '.[0].name')
           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 &
           export TEST_SIGSTORE_TIMESTAMP_AUTHORITY_URL="http://localhost:3000/api/v1/timestamp"
+
           # Ensure Timestamp Authority tests are not skipped by
           # 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:
+          # Needed for `gh api` above.
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
       - name: test (interactive)
         if: (github.event_name != 'pull_request') || !github.event.pull_request.head.repo.fork