Only build documentation if files under docs folder changed

Author: r0qs

.circleci/config.yml

@@ -6,6 +6,9 @@
 #     - ubu: ubuntu
 #     - ems: Emscripten
 version: 2.1
+
+setup: true
+
 parameters:
   ubuntu-2004-docker-image:
     type: string
@@ -35,9 +38,15 @@ parameters:
   evm-version:
     type: string
     default: prague
+  # Path filtering parameters
+  # Documentation workflow
+  run-docs-workflow:
+    type: boolean
+    default: false
 
 orbs:
   win: circleci/[email protected]
+  path-filtering: circleci/[email protected]
 
 commands:
   matrix_notify_unless_pr:
@@ -1872,6 +1881,20 @@ jobs:
 workflows:
   version: 2
 
+  setup:
+    jobs:
+      - path-filtering/filter:
+          name: filter-docs
+          mapping: |
+            docs/.* run-docs-workflow true
+          base-revision: develop
+          config-path: .circleci/config.yml
+
+  docs:
+    when: << pipeline.parameters.run-docs-workflow >>
+    jobs:
+      - b_docs: *requires_nothing
+
   main:
     jobs:
       # basic checks
@@ -1887,8 +1910,6 @@ workflows:
       - t_ubu_pyscripts: *requires_nothing
       - t_win_pyscripts: *requires_nothing
 
-      # build-only
-      - b_docs: *requires_nothing
       - b_ubu_ossfuzz: *requires_nothing
       - b_ubu_2204: *requires_nothing
       - b_ubu_2204_clang: *requires_nothing