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+================================================
+input: automatise commands using external inputs
+================================================
+
+``input`` is a way to use external data (like file in a specific format) as input
+arguments. It may be seen as a something similar to ``--output`` but for inputs.
+
+
+csv
+===
+
+CSV (for Comma-Separated Values) is a common format for tabular data. It is widely used in
+spreadsheet software (at least at en export format). With ``csv`` command, you can use
+columns a CSV file as arguments to jp commands.
+
+To set the command, you'll write in sequence what to do with each column of your data.
+For each column you can:
+
+- specify a short option name using ``-s ARGUMENTS, --short ARGUMENTS`` (short options are
+  the ones with a single ``-``)
+- specify a long option name using ``-l ARGUMENTS, --long ARGUMENTS`` (long options are
+  the ones with two ``-``)
+- specify a positional argument using ``-p ARGUMENTS, --positional ARGUMENTS``
+- indicate to use the column data with ``stdin`` using ``-i, --stdin``
+- ignore the column if it's not used in the jp command, using ``-x, --ignore``
+
+After each column specification, you may use a filter to manage the value. So far the
+following filters are available:
+
+``-S, --split``
+  This will split the value (on any whitespace character, discarding empty values) and
+  repeat the option which each item. This is useful when you are using an option which can
+  be repeated (like ``-t TAG, --tag TAG`` with ``jp blog set``).
+
+``-E ARGUMENTS, --empty ARGUMENTS``
+  Indicate what to do if the column value is empty (by default en empty string is used).
+  You can use either ``skip`` to skip the whole row, or ``ignore`` so the option will not
+  be set at all (which is different from the default which will still set the option but
+  with an empty string).
+
+CSV file is read from stdin, and by default unicode is expected. You may force an encoding
+by using ``--encoding ENCODING``.
+
+By default all the rows are read, but you may want to ignore first rows (if they are used
+for columns title, or if you have already handled part of the list). To do that, use the
+``-r ROW, --row ROW`` option.
+
+When you test your command, it is better to do a dry run to see what will happen. The
+``-D, --debug`` option is here for that: if you set it, the commands won't be actually
+run, but the exact command which would be executed will be printed on screen. You should
+always use this option first until you're sure that what you want will be executed.
+
+You may add verbosity level to help debugging. With a verbosity level of 2 (i.e. ``-vv``)
+the value read from CSV will be printed.
+
+By default stdout and stderr of each launched command is ignored, but you can log them to
+files using respectively ``--log LOG`` and ``--log-err LOG_ERR`` where ``LOG`` and
+``LOG_ERR`` are paths to a log file to create.
+
+Once all the sequence and options are set, you write the jp command that you want to use,
+with all the needed static option (i.e. options which must be used each time).
+
+
+example
+-------
+
+Louise as a spreadsheet with a table like this:
+
+============================  ============  =============  ===============
+title                         body          internal data  tags
+============================  ============  =============  ===============
+Some title                    a body        ABC            jp demo
+Something else                another body  XYZ            jp demo
+Third one                     third body    VWZ            special_tag jp
+This one doesn't have a body                123            jp demo numbers
+last one                      last body     456            jp demo numbers
+============================  ============  =============  ===============
+
+She wants to use it as input data to create blog posts.
+
+She first saves the file using CSV format, let's say to ``~/blog_input.csv``.
+
+Then she checks ``jp blog set --help`` to get name of options to use. She'll need to use
+``--title`` for title, ``stdin`` for the body and ``-t`` for tags. Louise wants to
+activate comments, so she also wants to use ``-C`` for all posts, and a tag to says it's
+coming from the spreadsheet (using ``-t spreadsheet``) .
+
+The first row of the table is used for columns headers, so she'll start at row 1 with ``-r
+1``.
+
+There is one row without body, Louise want to skip any row without body so she'll use the
+``-E skip`` filter, just after specifying the body row.
+
+Reading column by column, the sequence is like this:
+
+``-l title``
+  a title which goes to the ``--title`` long option of ``jp blog``
+``-i -E skip``
+  a body which goes to the stdin of ``jp blog``. If the body is empty, the ``-E skip``
+  filter tells to skip the whole row.
+``-x``
+  the ``internal data`` column is not used, so it is ignored
+``-s t -S``
+  the last column are the tags, so the ``-t`` short option is used. There are several of
+  them separated by spaces, so the ``-S`` filter is used to split the values.
+
+First she'll use the ``-D, --debug`` to check that the commands which will be executed are
+the expected one::
+
+  $ jp input csv -D -r 1 -l title -i -E skip -x -s t -S blog set -C -t spreadsheet < ~/blog_input.csv
+
+Everything seems fine, so she'll actually launch the command by running the same command
+line but without the ``-D`` option::
+
+  $ jp input csv -r 1 -l title -i -E skip -x -s t -S blog set -C -t spreadsheet < ~/blog_input.csv
+
+She could also have used ``--log`` and ``--log-err`` to check the logs of each command::
+
+  $ jp input csv -r 1 -l title -i -E skip -x -s t -S --log /tmp/jp_blog_stdout.log --log-err /tmp/jp_blog_stderr.log blog set -C -t spreadsheet < ~/blog_input.csv