This is a rewrite of the regex that handles Emacs modeline matching. The
current one is a little flaky, causing some files to be misclassified as
"E", among other things.
It's worth noting malformed modelines can still change a file's language
in Emacs. Provided the -*- delimiters are intact, and the mode's name is
decipherable, Emacs will set the appropriate language mode *and* display
a warning about a malformed modeline:
-*- foo-bar mode: ruby -*- # Malformed, but understandable
-*- mode: ruby--*- # Completely invalid
The new pattern accommodates this leniency, making no effort to validate
a modeline's syntax beyond readable mode-names. In other words, if Emacs
accepts certain errors, we should too.
The current expressions fail to match certain permutations of options:
vim: noexpandtab: ft=javascript:
vim: titlestring=foo\ ft=notperl ft=javascript:
Version-specific modelines are also unaccounted for:
vim600: set foldmethod=marker ft=javascript: # >= Vim 6.0
vim<600: set ft=javascript: # < Vim 6.0
See http://vimdoc.sourceforge.net/htmldoc/options.html#modeline
TLDR: This greatly increases the flexibility of vim modeline detection
to manually set the language of a file.
In vim there are two forms of modelines:
[text]{white}{vi:|vim:|ex:}[white]{options}
examples: 'vim: syntax=perl', 'ex: filetype=ruby'
-and-
[text]{white}{vi:|vim:|Vim:|ex:}[white]se[t] {options}:[text]
examples: 'vim set syntax=perl:', 'Vim: se ft=ruby:'
As you can see, there are many combinations. These changes should allow
most combinations to be used. The two most important additions are the
use of the keyword 'syntax', as well as the addition of the first form
(you now no longer need to use the keyword 'set' with a colon at the end).
The use of first form with 'syntax' is very, very common across GitHub:
https://github.com/search?l=ruby&q=vim%3A+syntax%3D&ref=searchresults&type=Code&utf8=%E2%9C%93
This change allows the filetype/language to be retrieved from more complex vim modelines. The current regex strictly allows a set line which contains only the filetype/ft parameter and nothing else
the emacs modeline is actually a per-file variable setting mechanism, which means it can have other flags in it.
this regex extracts the part that corresponds to the file's language ("mode:" - ie emacs major mode)
http://ergoemacs.org/emacs_manual/emacs/Specifying-File-Variables.html
