feat!: change the default of --forbid-only to check for process.env.CI

Author: RobinVdBroeck

docs/index.md

@@ -947,6 +947,12 @@ Enforce a rule that tests may not be exclusive (use of e.g., `describe.only()` o
 
 `--forbid-only` causes Mocha to fail when an exclusive ("only'd") test or suite is encountered, and it will abort further test execution.
 
+Defaults:
+
+1. Before v12: false
+2. After v12: false, unless an environment variable called `CI` is set. Many popular
+   CI providers, like github actions or gitlab, do this automatically.
+
 ### `--forbid-pending`
 
 Enforce a rule that tests may not be skipped (use of e.g., `describe.skip()`, `it.skip()`, or `this.skip()` anywhere is disallowed).

lib/cli/run.js

@@ -123,7 +123,8 @@ exports.builder = yargs =>
       },
       'forbid-only': {
         description: 'Fail if exclusive test(s) encountered',
-        group: GROUPS.RULES
+        group: GROUPS.RULES,
+        default: !!process.env.CI,
       },
       'forbid-pending': {
         description: 'Fail if pending test(s) encountered',

package.json

@@ -81,10 +81,10 @@
     "test-node:interfaces:tdd": "npm run -s test-node-run -- --ui tdd test/interfaces/tdd.spec",
     "test-node:interfaces": "run-p test-node:interfaces:*",
     "test-node:jsapi": "node test/jsapi/index.js",
-    "test-node:only:bddRequire": "npm run -s test-node-run-only -- --ui qunit test/only/bdd-require.spec --no-parallel",
-    "test-node:only:globalBdd": "npm run -s test-node-run-only -- --ui bdd test/only/global/bdd.spec --no-parallel",
-    "test-node:only:globalQunit": "npm run -s test-node-run-only -- --ui qunit test/only/global/qunit.spec --no-parallel",
-    "test-node:only:globalTdd": "npm run -s test-node-run-only -- --ui tdd test/only/global/tdd.spec --no-parallel",
+    "test-node:only:bddRequire": "npm run -s test-node-run-only -- --ui qunit test/only/bdd-require.spec --no-parallel --no-forbid-only",
+    "test-node:only:globalBdd": "npm run -s test-node-run-only -- --ui bdd test/only/global/bdd.spec --no-parallel --no-forbid-only",
+    "test-node:only:globalQunit": "npm run -s test-node-run-only -- --ui qunit test/only/global/qunit.spec --no-parallel --no-forbid-only",
+    "test-node:only:globalTdd": "npm run -s test-node-run-only -- --ui tdd test/only/global/tdd.spec --no-parallel --no-forbid-only",
     "test-node:only": "run-p test-node:only:*",
     "test-node:reporters": "npm run -s test-node-run -- \"test/reporters/*.spec.js\"",
     "test-node:requires": "npm run -s test-node-run -- --require coffeescript/register --require test/require/a.js --require test/require/b.coffee --require test/require/c.js --require test/require/d.coffee test/require/require.spec.js",