meta(gha): Deploy action validate-new-issue.yml (getsentry#849)

I are a bot, here to deploy [validate-new-issue.yml](https://github.com/getsentry/.github/blob/f663e1dd631880fa51cba2126f6192c92826c437/.github/workflows/validate-new-issue.yml). 🤖

.github/workflows/validate-new-issue.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - name: "Validate issue against templates"
+      - name: "Validate new issue"
         shell: bash
         env:
           GITHUB_TOKEN: ${{ github.token }}
@@ -22,43 +22,59 @@ jobs:
             echo "${{ github.actor }} is not a member of the getsentry org. 🧐"
           fi
 
-          # Look for a template where all the headings are also in this issue.
-          # - extra headings in the issue are fine
-          # - order doesn't matter
-          # - case-sensitive tho
-          # - can't post a template unchanged (ignoring whitespace)
+          # Prep reasons for error message comment.
+          REASON="your issue does not properly use one of this repo's available issue templates"
+          REASON_EXACT_MATCH="you created an issue from a template without filling in anything"
+          REASON_EMPTY="you created an empty issue"
+
+          # Definition of valid:
+          # - not empty (ignoring whitespace)
+          # - matches a template
+          #   - all the headings are also in this issue
+          #   - extra headings in the issue are fine
+          #   - order doesn't matter
+          #   - case-sensitive tho
+          # - not an *exact* match for a template (ignoring whitespace)
           function extract-headings { { sed 's/\r$//' "$1" | grep '^#' || echo -n ''; } | sort; }
           jq -r .issue.body "$GITHUB_EVENT_PATH" > issue
-          extract-headings <(cat issue) > headings-in-issue
-          for template in $(ls .github/ISSUE_TEMPLATE/*.md 2> /dev/null); do
-            # Strip front matter. https://stackoverflow.com/a/29292490/14946704
-            sed -i'' '1{/^---$/!q;};1,/^---$/d' "$template"
-            extract-headings "$template" > headings-in-template
-            echo -n "$(basename $template)? "
-            if [ ! -s headings-in-template ]; then
-              echo "No headers in template. 🤷"
-            elif [ -z "$(comm -23 headings-in-template headings-in-issue)" ]; then
-              echo "Match! 👍 💃"
-              if diff -Bw "$template" issue > /dev/null; then
-                echo "... like, an /exact/ match. 😖"
-                break
+          if ! grep -q '[^[:space:]]' issue; then
+            REASON="${REASON_EMPTY}"
+          else
+            extract-headings <(cat issue) > headings-in-issue
+            for template in $(ls .github/ISSUE_TEMPLATE/*.md 2> /dev/null); do
+              # Strip front matter. https://stackoverflow.com/a/29292490/14946704
+              sed -i'' '1{/^---$/!q;};1,/^---$/d' "$template"
+              extract-headings "$template" > headings-in-template
+              echo -n "$(basename $template)? "
+              if [ ! -s headings-in-template ]; then
+                echo "No headers in template. 🤷"
+              elif [ -z "$(comm -23 headings-in-template headings-in-issue)" ]; then
+                echo "Match! 👍 💃"
+                if diff -Bw "$template" issue > /dev/null; then
+                  echo "... like, an /exact/ match. 😖"
+                  REASON="${REASON_EXACT_MATCH}"
+                  break
+                else
+                  exit 0
+                fi
               else
-                exit 0
+                echo "No match. 👎"
               fi
-            else
-              echo "No match. 👎"
-            fi
-          done
+            done
+          fi
 
-          # Failed to find a match! Close the issue.
+          # Failed validation! Close the issue with a comment.
           cat << EOF > comment
-          Sorry, friend. As far as this ol' bot can tell, your issue does not use one of this repo's available issue templates. Please [try again using a template](https://github.com/${{ github.repository }}/issues/new/choose) so that we have the best chance of understanding and addressing your issue. (And if I'm confused, please [let us know](https://github.com/getsentry/.github/issues/new?title=template+enforcer+is+confused&body=${{ github.event.issue.html_url }}). 😬)
+          Sorry, friend. As far as this ol' bot can tell, ${REASON}. Please [try again](https://github.com/${{ github.repository }}/issues/new/choose), if you like. (And if I'm confused, please [let us know](https://github.com/getsentry/.github/issues/new?title=template+enforcer+is+confused&body=${{ github.event.issue.html_url }}). 😬)
 
           ----
 
-          [![Did you see the memo about this?](https://user-images.githubusercontent.com/134455/104515469-e04a9c80-55c0-11eb-8e15-ffe9c0b8dd7f.gif)](https://www.youtube.com/watch?v=Fy3rjQGc6lA)"
+          [![Did you see the memo about this?](https://user-images.githubusercontent.com/134455/104515469-e04a9c80-55c0-11eb-8e15-ffe9c0b8dd7f.gif)](https://www.youtube.com/watch?v=Fy3rjQGc6lA)
+
+          ([log](https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}))
           EOF
 
           echo -n "Commented: "
           gh issue comment ${{ github.event.issue.number }} --body "$(cat comment)"
           gh issue close ${{ github.event.issue.number }}
+          echo "Closed with: \"${REASON}.\""