b5227d8 changes meaning of "ls-files -x 'pattern'"

Hello,

Before b5227d8, the following two commands would produce different
outputs (say on git.git):

    git ls-files
    git ls-files -x '*.c'

From b5227d8 onward, they produce the same output.  The second command

no longer excludes *.c files.

I was unable to understand the commit message completely but it sounds
like this was intentionally changed to do this.

I've never been real clear on ls-files, and was wondering if someone
would be able to clarify the various ways of using it, including why
this change was made and is there a way (using some other combination of
flags perhaps) to get a list of files without *.c (to continue this
example).

Thanks,

Sitaram