github/workflow: do not override <clang++,23,release>

before this change, we

* override the combination of <clang++,23,release>
  by adding settings to build with dpdk enabled,
* override the combination of <clang++,23,debug>
  by adding settings to build with C++20 moduels
  enabled.

but what we intended was to add two additional
builds.

so, in this change, we preserve the existing
combinations of <clang++,23,release> and
<clang++,23,debug> by "include" <clang++,23,release>
explicitly, and by adding extra settings to
this setting twice with different settings.

see also https://docs.github.com/en/actions/using-jobs/using-a-matrix-for-your-jobs

also remove the confusing comment

based on the feedback of reviewer,

> the phrase "only build this combination when dpdk is enable" confusing
> - the phrase "in addition to the above" says the opposite, that we did
> build this combination without dpdk but now we'll build it again with
> dpdk.

Signed-off-by: Kefu Chai <[email protected]>

.github/workflows/tests.yaml

@@ -21,22 +21,26 @@ jobs:
         standard: [20, 23]
         mode: [dev, debug, release]
         include:
-          # in addition to the above combinations, add a combination to build with
-          # dpdk. but only build this combination when dpdk is enabled, so we don't
-          # double the size of the test matrix, and can at least test the build
-          # with dpdk enabled.
+          # preserve the existing <clang++18, C++23, release> combination
+          - compiler: clang++-18
+            standard: 23
+            mode: release
+            cooks:
+            enables:
+          # add "dpdk" to <clang++18, C++23, release>, so it builds with dpdk, as
+          # we don't want to double the size of the test matrix, and can at least
+          # test the build with dpdk enabled.
           - compiler: clang++-18
             standard: 23
             mode: release
             cooks: --cook dpdk
             enables: --enable-dpdk
-          # in addition to the above combinations, add a combination to build with
-          # C++20 modules. but only build this combination with C++20 modules enabled,
-          # so we don't double the size of the test matrix, and can at least test the
-          # build with C++20 modules enabled.
+          # add "--enable-cxx-modules" to <clang++18, C++23, release>, to build
+          # with C++20 modules, so we don't double the size of the test matrix,
+          # and can at least test the build with C++20 modules enabled.
           - compiler: clang++-18
             standard: 23
-            mode: debug
+            mode: release
             enables: --enable-cxx-modules
     steps:
       - uses: actions/checkout@v4