Add support for multiple bors targets.

Allow using `bors try --target ... --target ...`, allowing multiple
arguments rather than just a single one.

.github/workflows/ci.yml

@@ -92,10 +92,25 @@ jobs:
             declare -a "bors_args=(${bors_args})"
           fi
 
-          if [[ "${bors_args[0]-}" == --target ]]; then
-            echo "Only running targets matching '${bors_args[1]}'."
+          targets=()
+          index=0
+          while [[ "${bors_args[$index]-}" == --target ]]; do
+            index=$(expr $index + 1)
+            targets+=("${bors_args[$index]}")
+            index=$(expr $index + 1)
+          done
+
+          selects=()
+          for target in "${targets[@]}"; do
+            selects+=(".target == \"${target}\"")
+          done
+          query=$(printf " or %s" "${selects[@]}")
+          query="${query:4}"
+
+          if [[ "${#targets[@]}" != "0" ]]; then
+            echo "Only running targets matching '${targets[@]}'."
             matrix="$(
-              target="${bors_args[1]}" yq --output-format json '[.[] | select(.target | test(env(target)))]' <<< "${matrix}"
+              yq --output-format json '[.[] | select('"${query}"')]' matrix.yaml <<< "${matrix}"
             )"
           else
             echo 'Running all targets.'