Add the beginning of a nonbreakingspace test

Copy and modify existing code to start moving toward a workable
test for NBSP and NNBSP characters.

doc/development/documentation/styleguide/index.md

@@ -654,6 +654,17 @@ When the docs are generated, the output is:
 
 To stop the command, press <kbd>Control</kbd>+<kbd>C</kbd>.
 
+### Spaces between words
+
+Use only standard spaces between words. The search engine for the documentation
+website doesn't split words separated with
+[non-breaking spaces](https://en.wikipedia.org/wiki/Non-breaking_space) when
+indexing, and fails to create expected individual search terms. Tests that search
+for certain words separated by regular spaces can't find words separated by
+non-breaking spaces.
+
+Tested in [`lint-doc.sh`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/scripts/lint-doc.sh).
+
 ## Lists
 
 - Always start list items with a capital letter, unless they're parameters or

scripts/lint-doc.sh

@@ -18,6 +18,21 @@ then
   ((ERRORCODE++))
 fi
 
+# Test for non-standard spaces (NBSP, NNBSP) in documentation.
+echo '=> Checking for non-standard spaces...'
+echo
+grep --extended-regexp --binary-file=without-match --recursive '[  ]' doc/ >/dev/null 2>&1
+if [ $? -eq 0 ]
+then
+  echo '✖ ERROR: Non-standard spaces (NBSP, NNBSP) should not be used in documentation.
+         https://docs.gitlab.com/ee/development/documentation/styleguide/index.html#spaces-between-words
+         Replace with standard spaces:' >&2
+  # Find the spaces, then add color codes with sed to highlight each NBSP or NNBSP in the output.
+  grep --extended-regexp --binary-file=without-match --recursive --color=auto '[  ]' doc \
+       | sed -e ''/ /s//`printf "\033[0;101m \033[0m"`/'' -e ''/ /s//`printf "\033[0;101m \033[0m"`/''
+  ((ERRORCODE++))
+fi
+
 # Ensure that the CHANGELOG.md does not contain duplicate versions
 DUPLICATE_CHANGELOG_VERSIONS=$(grep --extended-regexp '^## .+' CHANGELOG.md | sed -E 's| \(.+\)||' | sort -r | uniq -d)
 echo '=> Checking for CHANGELOG.md duplicate entries...'