Verify a file's conformance with its modeline

[Ryan Schmidt]

Is there a command line tool that will verify that a file conforms  
with its modeline? For example, if a modeline says the file uses 4  
spaces for indentation (like our portfiles and other source should),  
but the file actually uses real tabs to indent, is there a tool that  
will point out this error? This is something that might be nice to  
add to port lint.

Not sure what else in the modeline needs verification. The modeline  
can/should specify the file's character encoding, but port lint  
always checks to make sure the file is UTF-8; it does not use the  
encoding listed in the modeline. Then again, neither does MacPorts  
itself; it also assumes/requires that the file is UTF-8.