ci: separate workflow for docs line len check (#6653)

.github/workflows/ci.yml

@@ -1,7 +1,16 @@
 name: CI
-on: [push, pull_request]
-jobs:
 
+on:
+  push:
+    paths-ignore:
+      - "doc/**"
+      - "CHANGELOG.md"
+  pull_request:
+    paths-ignore:
+      - "doc/**"
+      - "CHANGELOG.md"
+
+jobs:
   code-formatting:
     runs-on: ubuntu-18.04
     env:
@@ -461,15 +470,6 @@ jobs:
 #    - name: v2 self compilation
 #      run: .\v.exe -o v2.exe cmd/v && .\v2.exe -o v3.exe cmd/v
 
-  docs-line-len-check:
-    runs-on: ubuntu-18.04
-    steps:
-    - uses: actions/checkout@v2
-    - name: Build
-      run: make
-    - name: Check docs line length
-      run: ./v run cmd/tools/check-md.v doc/docs.md CHANGELOG.md
-
 
   compilable-v-c-and-v-win-c:
     runs-on: ubuntu-latest

.github/workflows/docs_ci.yml

@@ -0,0 +1,23 @@
+name: Docs CI
+
+on:
+  push:
+    paths:
+      - "cmd/tools/check-md.v"
+      - "doc/**"
+      - "CHANGELOG.md"
+  pull_request:
+    paths:
+      - "cmd/tools/check-md.v"
+      - "doc/**"
+      - "CHANGELOG.md"
+
+jobs:
+  docs-line-len-check:
+    runs-on: ubuntu-18.04
+    steps:
+    - uses: actions/checkout@v2
+    - name: Build V
+      run: make
+    - name: Check docs line length
+      run: ./v run cmd/tools/check-md.v doc/docs.md doc/upcoming.md CHANGELOG.md