Update docs for setting verbose/quite in config file or env var

docs/html/user_guide.rst

@@ -440,6 +440,15 @@ and ``--no-cache-dir``, falsy values have to be used:
     no-compile = no
     no-warn-script-location = false
 
+For options which can be repeated like ``--verbose`` and ``--quite``,
+a nonnegative integer could be used to represent the level to be specified:
+
+.. code-block:: ini
+
+    [global]
+    quite = 0
+    verbose = 2
+
 It is possible to append values to a section within a configuration file such as the pip.ini file.
 This is applicable to appending options like ``--find-links`` or ``--trusted-host``,
 which can be written on multiple lines:
@@ -469,20 +478,20 @@ pip's command line options can be set with environment variables using the
 format ``PIP_<UPPER_LONG_NAME>`` . Dashes (``-``) have to be replaced with
 underscores (``_``).
 
-For example, to set the default timeout::
-
-    export PIP_DEFAULT_TIMEOUT=60
-
-This is the same as passing the option to pip directly::
+For example, setting ``PIP_DEFAULT_TIMEOUT`` to 60 has the same effect as
+passing the option to pip directly::
 
     pip --default-timeout=60 [...]
 
-For command line options which can be repeated, use a space to separate
-multiple values. For example::
-
-    export PIP_FIND_LINKS="http://mirror1.example.com http://mirror2.example.com"
+For command line options which can be repeated, if they do not take any argument
+like ``--quite`` or ``--verbose``, use a nonnegative integer to represent
+the number of repeatition, for instance setting ``PIP_VERBOSE`` to 3 is
+equivalent to calling pip with ``-vvv``.
 
-is the same as calling::
+Fruitful repeatable options however, can be specified via environment variable
+as a space-separated list.  For example having ``PIP_FIND_LINKS`` set to
+``"http://mirror1.example.com http://mirror2.example.com"`` is the same as
+calling ::
 
     pip install --find-links=http://mirror1.example.com --find-links=http://mirror2.example.com