docs: better description of ignores (#3692)

docs/reference-configuration.md

@@ -40,11 +40,20 @@ const Configuration = {
     'type-enum': [2, 'always', ['foo']],
   },
   /*
-   * Functions that return true if commitlint should ignore the given message.
+   * Array of functions that return true if commitlint should ignore the given message.
+   * Given array is merged with predefined functions, which consist of matchers like:
+   *
+   * - 'Merge pull request', 'Merge X into Y' or 'Merge branch X'
+   * - 'Revert X'
+   * - 'v1.2.3' (ie semver matcher)
+   * - 'Automatic merge X' or 'Auto-merged X into Y'
+   *
+   * To see full list, check https://github.com/conventional-changelog/commitlint/blob/master/%40commitlint/is-ignored/src/defaults.ts.
+   * To disable those ignores and run rules always, set `defaultIgnores: false` as shown below.
    */
   ignores: [(commit) => commit === ''],
   /*
-   * Whether commitlint uses the default ignore rules.
+   * Whether commitlint uses the default ignore rules, see the description above.
    */
   defaultIgnores: true,
   /*