rules: add line-after-title rule (#7)

This rule ensures that the body is not empty and that there is a blank
line after the commit title

Semver: major

Author: evanlucas

lib/rules/line-after-title.js

@@ -0,0 +1,34 @@
+'use strict'
+
+const id = 'line-after-title'
+
+module.exports = {
+  id: id
+, meta: {
+    description: 'enforce a blank newline after the commit title'
+  , recommended: true
+  }
+, defaults: {}
+, options: {}
+, validate: (context, rule) => {
+    // all commits should have a body and a blank line after the title
+    if (!context.body.length || context.body[0]) {
+      context.report({
+        id: id
+      , message: 'blank line expected after title'
+      , string: context.body.length ? context.body[0] : ''
+      , line: 1
+      , column: 0
+      , level: 'fail'
+      })
+      return
+    }
+
+    context.report({
+      id: id
+    , message: 'blank line after title'
+    , string: ''
+    , level: 'pass'
+    })
+  }
+}

test/validator.js

@@ -211,12 +211,13 @@ test('Validator - real commits', (t) => {
       const filtered = msgs.filter((item) => {
         return item.level === 'fail'
       })
-      tt.equal(filtered.length, 2, 'messages.length')
-      tt.equal(filtered[0].id, 'pr-url', 'message id')
-      tt.equal(filtered[0].string, '#5546', 'message string')
-      tt.equal(filtered[1].id, 'subsystem', 'message id')
-      tt.equal(filtered[1].line, 0, 'line')
-      tt.equal(filtered[1].column, 0, 'column')
+      tt.equal(filtered.length, 3, 'messages.length')
+      tt.equal(filtered[0].id, 'line-after-title', 'message id')
+      tt.equal(filtered[1].id, 'pr-url', 'message id')
+      tt.equal(filtered[1].string, '#5546', 'message string')
+      tt.equal(filtered[2].id, 'subsystem', 'message id')
+      tt.equal(filtered[2].line, 0, 'line')
+      tt.equal(filtered[2].column, 0, 'column')
       tt.end()
     })
   })