Move all lua related files to lua/ subfolder

Also remove the lexers sub directory from the Lua search path.
As a result we attempt to open fewer files during startup:

 $ strace -e open -o log ./vis +q config.h && wc -l log

In order to avoid having to modifiy all lexers which `require('lexer')`
we instead place a symlink in the top level directory.

 $ ./configure --disable-lua
 $ rm -rf lua

Should result in a source tree with most lua specifc functionality
removed.

1 files changed, 44 insertions, 0 deletions

diff --git a/lua/lexers/diff.lua b/lua/lexers/diff.lua
new file mode 100644
index 0000000..9bc63f1
--- /dev/null
+++ b/lua/lexers/diff.lua
@@ -0,0 +1,44 @@
+-- Copyright 2006-2016 Mitchell mitchell.att.foicica.com. See LICENSE.
+-- Diff LPeg lexer.
+
+local l = require('lexer')
+local token, word_match = l.token, l.word_match
+local P, R, S = lpeg.P, lpeg.R, lpeg.S
+
+local M = {_NAME = 'diff'}
+
+-- Text, separators, and file headers.
+local index = token(l.COMMENT, 'Index: ' * l.any^0 * P(-1))
+local separator = token(l.COMMENT, ('---' + P('*')^4 + P('=')^1) * l.space^0 *
+                                   -1)
+local header = token('header', (P('*** ') + '--- ' + '+++ ') * l.any^1)
+
+-- Location.
+local location = token(l.NUMBER, ('@@' + l.digit^1 + '****') * l.any^1)
+
+-- Additions, deletions, and changes.
+local addition = token('addition', S('>+') * l.any^0)
+local deletion = token('deletion', S('<-') * l.any^0)
+local change   = token('change', '! ' * l.any^0)
+
+M._rules = {
+  {'index', index},
+  {'separator', separator},
+  {'header', header},
+  {'location', location},
+  {'addition', addition},
+  {'deletion', deletion},
+  {'change', change},
+  {'any_line', token('default', l.any^1)},
+}
+
+M._tokenstyles = {
+  header = l.STYLE_COMMENT,
+  addition = 'fore:green',
+  deletion = 'fore:red',
+  change = 'fore:yellow',
+}
+
+M._LEXBYLINE = true
+
+return M