Update common github actions

Signed-off-by: Knative Automation <automation@knative.team>

.github/workflows/knative-releasability.yaml

@@ -36,8 +36,8 @@ jobs:
     env:
       #########################################
       #   Update this section each release.   #
-      RELEASE: 'v0.19'
-      SLACK_CHANNEL: 'release-19'
+      RELEASE: 'v0.20'
+      SLACK_CHANNEL: 'release-20'
       #########################################
 
     steps:
@@ -50,6 +50,9 @@ jobs:
           if [[ "${{ github.event.inputs.slackChannel }}" != "" ]]; then
             echo "SLACK_CHANNEL=${{ github.event.inputs.slackChannel }}" >> $GITHUB_ENV
           fi
+          if [[ "${{ secrets.SLACK_WEBHOOK }}" != "" ]]; then
+            echo "SLACK_WEBHOOK=exists" >> $GITHUB_ENV
+          fi
 
       - name: Set up Go 1.15.x
         uses: actions/setup-go@v2
@@ -142,7 +145,8 @@ jobs:
           echo 'SLACK_TITLE=Releasability for ${{ github.repository }} @ ${{ env.RELEASE }} is NO-GO!' >> $GITHUB_ENV
 
       - name: Post status to Slack
-        if: ${{ secrets.SLACK_WEBHOOK != '' && steps.exists.outputs.release-branch == 'false' }}
+        # Note: using env.SLACK_WEBHOOK here because secrets are not allowed in the if block.
+        if: env.SLACK_WEBHOOK != '' && steps.exists.outputs.release-branch == 'false'
         uses: rtCamp/action-slack-notify@v2.1.0
         env:
           SLACK_ICON: http://github.com/knative.png?size=48

.github/workflows/knative-style.yaml

@@ -141,7 +141,12 @@ jobs:
           echo '::group:: Running github.com/client9/misspell with reviewdog 🐶 ...'
           # Don't fail because of misspell
           set +o pipefail
-          find . -type f -not -path './vendor/*' -not -path './third_party/*' -not -path './.git/*' |
+          # Exclude generated and vendored files, plus some legacy
+          # paths until we update all .gitattributes
+          git ls-files |
+          git check-attr --stdin linguist-generated | grep -Ev ': (set|true)$' | cut -d: -f1 |
+          git check-attr --stdin linguist-vendored | grep -Ev ': (set|true)$' | cut -d: -f1 |
+          grep -Ev '^(vendor/|third_party/|.git)' |
           xargs misspell -error |
           reviewdog -efm="%f:%l:%c: %m" \
                 -name="github.com/client9/misspell" \
@@ -164,7 +169,13 @@ jobs:
           echo '::group:: Flagging trailing whitespace with reviewdog 🐶 ...'
           # Don't fail because of grep
           set +o pipefail
-          find . -type f -not -path './vendor/*' -not -path './third_party/*' -not -path './.git/*' |
+          
+          # Exclude generated and vendored files, plus some legacy
+          # paths until we update all .gitattributes
+          git ls-files |
+          git check-attr --stdin linguist-generated | grep -Ev ': (set|true)$' | cut -d: -f1 |
+          git check-attr --stdin linguist-vendored | grep -Ev ': (set|true)$' | cut -d: -f1 |
+          grep -Ev '^(vendor/|third_party/|.git)' |
           xargs grep -nE " +$" |
           reviewdog -efm="%f:%l:%m" \
                 -name="trailing whitespace" \
@@ -192,7 +203,13 @@ jobs:
           #  - nothing in third_party
           #  - nothing in .git/
           #  - no *.ai (Adobe Illustrator) files.
-          for x in $(find . -type f -not -name '*.ai' -not -path './vendor/*' -not -path './third_party/*' -not -path './.git/*'); do
+          LINT_FILES=$(git ls-files |
+          git check-attr --stdin linguist-generated | grep -Ev ': (set|true)$' | cut -d: -f1 |
+          git check-attr --stdin linguist-vendored | grep -Ev ': (set|true)$' | cut -d: -f1 |
+          grep -Ev '^(vendor/|third_party/|.git)' |
+          grep -v '\.ai$')
+
+          for x in $LINT_FILES; do
             # Based on https://stackoverflow.com/questions/34943632/linux-check-if-there-is-an-empty-line-at-the-end-of-a-file
             if [[ -f $x && ! ( -s "$x" && -z "$(tail -c 1 $x)" ) ]]; then
               # We add 1 to `wc -l` here because of this limitation (from the man page):