Stop running testsuites when only the book is modified (#6956)

ci/affects-files.sh

@@ -8,6 +8,8 @@
 #     ./affects-files.sh .rs     -- also matches foo.rs.bar
 #     ./affects-files.sh ^snap/  -- anything under the snap/ subdirectory
 #     ./affects-files.sh snap/   -- also matches foo/snap/
+# Any pattern starting with the ! character will be negated:
+#     ./affects-files.sh !^book/  -- anything *not* under the book/ subdirectory
 #
 set -e
 cd "$(dirname "$0")"/..
@@ -18,11 +20,19 @@ if [[ -n $CI_PULL_REQUEST ]]; then
 
   IFS=':' read -ra files <<< "$affectedFiles"
   for pattern in "$@"; do
-    for file in "${files[@]}"; do
-      if [[ $file =~ $pattern ]]; then
-        exit 0
-      fi
-    done
+    if [[ ${pattern:0:1} = "!" ]]; then
+      for file in "${files[@]}"; do
+        if [[ ! $file =~ ${pattern:1} ]]; then
+          exit 0
+        fi
+      done
+    else
+      for file in "${files[@]}"; do
+        if [[ $file =~ $pattern ]]; then
+          exit 0
+        fi
+      done
+    fi
   done
 
   exit 1