ci: fix coverage parsing and JSON payload construction

.drone.yml

@@ -23,9 +23,8 @@ steps:
         from_secret: gitea_token
     commands:
       - apt-get update -qq && apt-get install -y -qq jq curl
-      - cargo tarpaulin --out Json 2>/dev/null
       - |
-        PCT=$(jq '(.covered / .coverable * 100) | floor' tarpaulin-report.json)
+        PCT=$(cargo tarpaulin 2>&1 | grep -oE '[0-9]+\.[0-9]+% coverage' | cut -d'.' -f1)
         if [ "$PCT" -ge 80 ]; then COLOR="brightgreen"
         elif [ "$PCT" -ge 60 ]; then COLOR="yellow"
         else COLOR="red"; fi
@@ -37,9 +36,13 @@ steps:
           | jq -r '.sha // empty')
         CONTENT=$(base64 -w 0 coverage.svg)
         if [ -n "$SHA" ]; then
-          PAYLOAD="{\"message\":\"ci: update coverage badge [CI SKIP]\",\"content\":\"$CONTENT\",\"sha\":\"$SHA\",\"branch\":\"master\"}"
+          PAYLOAD=$(jq -n --arg msg "ci: update coverage badge [CI SKIP]" \
+            --arg content "$CONTENT" --arg sha "$SHA" --arg branch "master" \
+            '{message: $msg, content: $content, sha: $sha, branch: $branch}')
         else
-          PAYLOAD="{\"message\":\"ci: add coverage badge [CI SKIP]\",\"content\":\"$CONTENT\",\"branch\":\"master\"}"
+          PAYLOAD=$(jq -n --arg msg "ci: add coverage badge [CI SKIP]" \
+            --arg content "$CONTENT" --arg branch "master" \
+            '{message: $msg, content: $content, branch: $branch}')
         fi
         curl -fsSL -X PUT \
           -H "Authorization: token $GITEA_TOKEN" \