ci: improve shellcheck job

1. Use env directive instead of adding to $GITHUB_ENV.

2. Use bash herefile to feed sha256sum instead of pipe to grep.

3. Fix the hardcoded checksum (it was missing the first character).

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

.github/workflows/validate.yml

@@ -90,24 +90,23 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v3
-      - name: vars
-        run: |
-          echo 'VERSION=v0.8.0' >> $GITHUB_ENV
-          echo 'BASEURL=https://github.com/koalaman/shellcheck/releases/download' >> $GITHUB_ENV
-          echo 'SHA256SUM=f4bce23c11c3919c1b20bcb0f206f6b44c44e26f2bc95f8aa708716095fa0651' >> $GITHUB_ENV
-          echo ~/bin >> $GITHUB_PATH
       - name: install shellcheck
+        env:
+          VERSION: v0.8.0
+          BASEURL: https://github.com/koalaman/shellcheck/releases/download
+          SHA256: f4bce23c11c3919c1b20bcb0f206f6b44c44e26f2bc95f8aa708716095fa0651
         run: |
           mkdir ~/bin
           curl -sSfL --retry 5 $BASEURL/$VERSION/shellcheck-$VERSION.linux.x86_64.tar.xz |
             tar xfJ - -C ~/bin --strip 1 shellcheck-$VERSION/shellcheck
-          sha256sum ~/bin/shellcheck | grep -q $SHA256SUM
+          sha256sum --strict --check - <<<"$SHA256 *$HOME/bin/shellcheck"
           # make sure to remove the old version
           sudo rm -f /usr/bin/shellcheck
+          # Add ~/bin to $PATH.
+          echo ~/bin >> $GITHUB_PATH
       - uses: lumaxis/shellcheck-problem-matchers@v1
-      - name: shellcheck
-        run: |
-          make shellcheck
+      - name: run
+        run: make shellcheck
       - name: check-config.sh
         run : ./script/check-config.sh