Add CI check for unecessary template tests

When the regression tests output differs between PG versions we create a
template test file (*.sql.in) and add several different output files for
each supported version.

Over time we support new PG version and deprecate older ones, for
example nowadays we're working on PG16 support and removed PG12 so we
need to check if we still need template files.

.github/workflows/code_style.yaml

@@ -100,7 +100,7 @@ jobs:
           git diff --exit-code
 
   misc_checks:
-    name: Check license, update scripts, git hooks and missing gitignore entries
+    name: Check license, update scripts, git hooks, missing gitignore entries and unecessary template tests
     runs-on: ubuntu-22.04
     strategy:
       fail-fast: false
@@ -124,3 +124,7 @@ jobs:
     - name: Check for missing gitignore entries for template test files
       if: always()
       run: ./scripts/check_missing_gitignore_for_template_tests.sh
+    - name: Check for unecessary template test files
+      if: always()
+      run: ./scripts/check_unecessary_template_tests.sh
+

scripts/check_unecessary_template_tests.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+
+ERROR=0
+
+for FILE in $(git ls-files test/sql/*.sql.in tsl/test/sql/*.sql.in)
+do
+  DIRNAME=$(dirname "${FILE}" | sed 's/sql/expected/g')
+  TESTNAME=$(basename "${FILE}" .sql.in)
+
+  if diff --from-file ${DIRNAME}/${TESTNAME}-*.out > /dev/null 2>&1; then
+      echo "ERROR: all template output test files are equal: \"${DIRNAME}/${TESTNAME}-*.out\""
+      echo "HINT: Please turn template test file \"${FILE}\" into a regular test file"
+      ERROR=1
+  fi
+done
+
+exit ${ERROR}