Add check for exec permissions and refactor lint doc script

scripts/lint-doc.sh

@@ -3,15 +3,19 @@
 cd "$(dirname "$0")/.."
 
 # Use long options (e.g. --header instead of -H) for curl examples in documentation.
-grep --extended-regexp --recursive --color=auto 'curl (.+ )?-[^- ].*' doc/
+echo 'Checking for curl short options...'
+grep --extended-regexp --recursive --color=auto 'curl (.+ )?-[^- ].*' doc/ >/dev/null 2>&1
 if [ $? == 0 ]
 then
-  echo '✖ ERROR: Short options should not be used in documentation!' >&2
+  echo '✖ ERROR: Short options for curl should not be used in documentation!
+         Use long options (e.g., --header instead of -H):' >&2
+  grep --extended-regexp --recursive --color=auto 'curl (.+ )?-[^- ].*' doc/
   exit 1
 fi
 
 # Ensure that the CHANGELOG.md does not contain duplicate versions
 DUPLICATE_CHANGELOG_VERSIONS=$(grep --extended-regexp '^## .+' CHANGELOG.md | sed -E 's| \(.+\)||' | sort -r | uniq -d)
+echo 'Checking for CHANGELOG.md duplicate entries...'
 if [ "${DUPLICATE_CHANGELOG_VERSIONS}" != "" ]
 then
   echo '✖ ERROR: Duplicate versions in CHANGELOG.md:' >&2
@@ -19,5 +23,16 @@ then
   exit 1
 fi
 
+# Make sure no files in doc/ are executable
+EXEC_PERM_COUNT=$(find doc/ -type f -perm 755 | wc -l)
+echo 'Checking for executable permissions...'
+if [ "${EXEC_PERM_COUNT}" -ne 0 ]
+then
+  echo '✖ ERROR: Executable permissions should not be used in documentation! Use `chmod 644` to the files in question:' >&2
+  echo
+  find doc/ -type f -perm 755
+  exit 1
+fi
+
 echo "✔ Linting passed"
 exit 0