CI: Check that Vim help tags in runtime folder are correct

Previously, Vim didn't always have up-to-date help tags. As a result, we
just manually generate the help tags when publishing a release (#1286),
even though it doesn't actually make sure the tags file in source is
actually accurate. However, Vim has since added CI checks to make sure
the help tags are correct, so we can change MacVim CI to do the same
thing as well. This way, the source version is always correct and we
won't rely on a build step during release to fix it, and it also makes
sure other methods to get MacVim (build from source, Homebrew) will be
correct as well.

.github/workflows/ci-macvim.yaml

@@ -53,6 +53,7 @@ jobs:
           # Oldest version of Xcode supported on GitHub Action to test source code backwards compatibility
           - os: macos-11
             xcode: '11.7'
+            extra: [vimtags]
 
           # Older version of Xcode, and used to publish legacy builds (for macOS 10.9 - 10.12)
           - os: macos-12
@@ -221,27 +222,7 @@ jobs:
           cat src/auto/config.mk
           cat src/auto/config.h
 
-      # Build Vim first, separately from MacVim, so that we can use it to run
-      # vimtags afterwards to get the most correct help tags before we copy
-      # that into the MacVim bundle.
-      - name: Build Vim
-        env:
-          LC_ALL: C
-        run: |
-          set -o verbose
-
-          NPROC=$(getconf _NPROCESSORS_ONLN)
-          echo "Building Vim with ${NPROC} cores"
-
-          make -C src -j${NPROC} Vim
-
-      # Re-generate Vim help tags, because sometimes the Vim's runtime is not
-      # updated to have the latest tags.
-      - name: Update Vim help tags
-        if: matrix.publish
-        run: make -C runtime/doc vimtags VIMEXE=../../src/vim
-
-      - name: Build MacVim
+      - name: Build
         env:
           LC_ALL: C
         run: |
@@ -313,6 +294,13 @@ jobs:
           check_arch "${VIM_BIN}"
           check_arch "${MACVIM_BIN}"
 
+      - name: Check Vim help tags
+        if: contains(matrix.extra, 'vimtags')
+        run: |
+          # Confirm that we can build the help tags, and they match what's in source.
+          make -C runtime/doc vimtags VIMEXE=../../${VIM_BIN}
+          git diff --exit-code -- runtime/doc/tags
+
       - name: Test
         timeout-minutes: 20
         run: make test