cli: Add the -d option to provide inline conf

docs/configuration.rst

@@ -8,7 +8,7 @@ settings can be gathered in a configuration file.
 To use a custom configuration file, either name it ``.yamllint`` in your working
 directory, or use the ``-c`` option:
 
-::
+.. code:: bash
 
  yamllint -c ~/myconfig file.yml
 
@@ -22,6 +22,15 @@ Unless told otherwise, yamllint uses its ``default`` configuration:
 
 Details on rules can be found on :doc:`the rules page <rules>`.
 
+There is another pre-defined configuration named ``relaxed``. As its name
+suggests, it is more tolerant.
+
+It can be chosen using:
+
+.. code:: bash
+
+ yamllint -d relaxed file.yml
+
 Extending the default configuration
 -----------------------------------
 
@@ -63,6 +72,21 @@ strict on block sequences indentation:
    indentation:
      indent-sequences: whatever
 
+Custom configuration without a config file
+------------------------------------------
+
+It is possible -- although not recommended -- to pass custom configuration
+options to yamllint with the ``-d`` (short for ``--config-data``) option.
+
+Its content can either be the name of a pre-defined conf (example: ``default``
+or ``relaxed``) or a serialized YAML object describing the configuration.
+
+For instance:
+
+.. code:: bash
+
+ yamllint -d "{extends: relaxed, rules: {line-length: {max: 120}}}" file.yml
+
 Errors and warnings
 -------------------