Make CL configurable via environment variable DIFF_CONTEXT

Author: Lethja

demo/xtra/DIFF.LUA

@@ -1,6 +1,6 @@
-#!/usr/bin/env lua
+#!/usr/bin/env lua
 
-CL = 3
+CL = tonumber(os.getenv("DIFF_CONTEXT")) or 3
 local function diff_u(fn1, fn2)
 	local function open(fn) local f, e = io.open(fn) if not f then print(e) os.exit(1) end return f end
 	local f1, f2, pre, add, del, p1, p2, x, y, h, l1, l2 = open(fn1), open(fn2), {}, {}, {}, 0, 0, 0, 0