Fix waittime metric for rebuilds

ci/build-helpers.sh

@@ -39,13 +39,21 @@ function report_state () {
     pr_processing_done) prtime=$((time_now - TIME_PR_STARTED));;
   esac
 
+  # If this is a rebuild, the last push time is mostly meaningless -- the PR
+  # hasn't been waiting since then for a check.
+  local waittime=
+  if [ -n "$LAST_PUSH_TIME" ] && [ "$BUILD_TYPE" != untested ]; then
+    waittime=$((time_now - LAST_PUSH_TIME))
+  fi
+
   # Push to InfluxDB if configured
   influxdb_push prcheck "repo=$PR_REPO" "checkname=$CHECK_NAME" \
                 "worker=$CHECK_NAME/$WORKER_INDEX/$WORKERS_POOL_SIZE" \
                 ${NUM_BASE_COMMITS:+"num_base_commits=$NUM_BASE_COMMITS"} \
+                "prev_build=$BUILD_TYPE" \
                 -- "host=\"$(hostname -s)\"" "state=\"$current_state\"" \
                 "prid=\"$PR_NUMBER\"" ${prtime:+prtime=$prtime} ${PR_OK:+prok=$PR_OK} \
-                ${LAST_PUSH_TIME:+waittime=$((time_now - LAST_PUSH_TIME))} \
+                ${waittime:+"waittime=$waittime"} \
                 ${HAVE_JALIEN_TOKEN:+have_jalien_token=$HAVE_JALIEN_TOKEN}
 
   # Push to Google Analytics if configured