Fix of ShellCheck and doc update. Int testing updates. Added ShellCheck action. (#3)

Co-authored-by: OCP4 migration script <deleng@atg.se>

hadolint.sh

@@ -5,14 +5,14 @@
 
 PROBLEM_MATCHER_FILE="/problem-matcher.json"
 if [ -f "$PROBLEM_MATCHER_FILE" ]; then
-    cp "$PROBLEM_MATCHER_FILE" "$HOME/"
+  cp "$PROBLEM_MATCHER_FILE" "$HOME/"
 fi
 # After the run has finished we remove the problem-matcher.json from
 # the repository so we don't leave the checkout dirty. We also remove
 # the matcher so it won't take effect in later steps.
 # shellcheck disable=SC2317
 cleanup() {
-    echo "::remove-matcher owner=brpaz/hadolint-action::"
+  echo "::remove-matcher owner=brpaz/hadolint-action::"
 }
 trap cleanup EXIT
 
@@ -23,7 +23,7 @@ if [ -n "$HADOLINT_CONFIG" ]; then
 fi
 
 if [ -z "$HADOLINT_TRUSTED_REGISTRIES" ]; then
-  unset HADOLINT_TRUSTED_REGISTRIES;
+  unset HADOLINT_TRUSTED_REGISTRIES
 fi
 
 COMMAND="hadolint $HADOLINT_CONFIG"
@@ -32,7 +32,6 @@ if [ "$HADOLINT_RECURSIVE" = "true" ]; then
   shopt -s globstar
 
   filename="${!#}"
-
   flags="${*:1:$#-1}"
 
   RESULTS=$(eval "$COMMAND $flags" -- **/"$filename")
@@ -46,14 +45,22 @@ if [ -n "$HADOLINT_OUTPUT" ]; then
   if [ -f "$HADOLINT_OUTPUT" ]; then
     HADOLINT_OUTPUT="$TMP_FOLDER/$HADOLINT_OUTPUT"
   fi
-  echo "$RESULTS" > "$HADOLINT_OUTPUT"
+  echo "$RESULTS" >"$HADOLINT_OUTPUT"
 fi
 
 RESULTS="${RESULTS//$'\\n'/''}"
 
-{ echo "results<<EOF"; echo "$RESULTS"; echo "EOF"; } >> "$GITHUB_OUTPUT"
+{
+  echo "results<<EOF"
+  echo "$RESULTS"
+  echo "EOF"
+} >>"$GITHUB_OUTPUT"
 
-{ echo "HADOLINT_RESULTS<<EOF"; echo "$RESULTS"; echo "EOF"; } >> "$GITHUB_ENV"
+{
+  echo "HADOLINT_RESULTS<<EOF"
+  echo "$RESULTS"
+  echo "EOF"
+} >>"$GITHUB_ENV"
 
 [ -z "$HADOLINT_OUTPUT" ] || echo "Hadolint output saved to: $HADOLINT_OUTPUT"