Add "Indentation from Makefile" to docs

[dch]

Indentation from a Makefile

This snippet as a make target will re-indent all src/*.?rl files for you.

reindent:
    @# requires either vim 7.4, or github.com/vim-erlang/vim-erlang-runtime
    @# add -c ':set runtimepath^=~/v/.vim/bundle/vim-erlang-runtime/' if less
    vim -E -N --noplugin -u /dev/null -c ':filetype plugin indent on' \
        -c ':args src/*.?rl' \
        -c 'argdo silent execute "normal gg=G"' \
        -c 'update' -c q

[hcs42]

Thanks. What do you mean by "add -c ':set runtimepath^=~/v/.vim/bundle/vim-erlang-runtime/' if less"?

[dch]

@hcs42 sorry!

I mean that if your vim is < 7.4, then IIRC it won't have the indenting rules that this repo includes, and therefore you'll need to include this repo into your vimpath, like so:

From the terminal you can then do (all in one go!):

vim -E -N --noplugin -u /dev/null -c ':filetype plugin indent on' \
  -c ':set runtimepath^=~/v/.vim/bundle/vim-erlang-runtime/' if less
  -c ':args src/*.?rl' \
  -c 'argdo silent execute "normal gg=G"' \
  -c 'update' -c q

[hcs42]

@dch: This is my proposal to add to README:

Tip: indentation from the command line

The following snippet re-indents all src/*.?rl files using the indentation shipped with Vim:

vim -ENn -u NONE \
    -c 'filetype plugin indent on' \
    -c 'set expandtab shiftwidth=4' \
    -c 'args src/*.?rl' \
    -c 'argdo silent execute "normal gg=G" | update' \
    -c q

Notes:

• This can be for example added to a Makefile as a "re-indent rule".

• You can use the expandtab, shiftwidth and tabstop options to customize
  how to use space and tab characters. The command above uses only spaces, and
  one level of indentation is 4 spaces.

• If you would like to use a different version of the indentation script from
  that one shipped in Vim (e.g. because you have Vim 7.3), then also add the
  following as the first command paramter:

  -c ':set runtimepath^=~/.vim/bundle/vim-erlang-runtime/'

Changes from the original one:

• I phrased it as a shell command instead of a Makefile rule. Since we don't use anything Makefile-specific, I think this gives a more clear first impression of what this command actually is (a shell call, as opposed to a Makefile rule). Also, I'm not sure I would encourage using it as a Makefile-rule, since the indentation is not perfect (see the type specs for example...)
• : consistently skipped in -c arguments.
• Custom runtimepath moved into a note.
• -n added (no swap file).
• -u NONE instead of --noplugin -u /dev/null. From :help -u: "When {vimrc} is equal to "NONE" (all uppercase), all initializations from files and environment variables are skipped, including reading the |gvimrc| file when the GUI starts. Loading plugins is also skipped."
• update moved into argdo. Otherwise for me it saved only the last file and complained that the others are not saved.
• I added a command and a note about expandtab, shiftwidth and tabstop.

What do you think?

[dch]

LGTM! And thanks for the improvements, your vim is much better than mine!

ship it :-)