[PATCH] Make "git-ls-files" work in subdirectories

[PATCH] Make "git-ls-files" work in subdirectories

This makes git-ls-files work inside a relative directory, and also adds
some rudimentary filename globbing support. For example, in the kernel you
can now do

	cd arch/i386
	git-ls-files

and it will show all files under that subdirectory (and it will have
removed the "arch/i386/" prefix unless you give it the "--full-name"
option, so that you can feed the result to "xargs grep" or similar).

The filename globbing is kind of strange: it does _not_ follow normal
globbing rules, although it does look "almost" like a normal file glob
(and it uses the POSIX.2 "fnmatch()" function).

The glob pattern (there can be only one) is always split into a "directory
part" and a "glob part", where the directory part is defined as any full
directory path without any '*' or '?' characters. The "glob" part is
whatever is left over.

For example, when doing

	git-ls-files 'arch/i386/p*/*.c'

the "directory part" is is "arch/i386/", and the "glob part" is "p*/*.c".
The directory part will be added to the prefix, and handled efficiently
(ie we will not be searching outside of that subdirectory), while the glob
part (if anything is left over) will be used to trigger "fnmatch()"
matches.

This is efficient and very useful, but can result in somewhat
non-intuitive behaviour.

For example:

	git-ls-files 'arch/i386/*.[ch]'

will find all .c and .h files under arch/i386/, _including_ things in
lower subdirectories (ie it will match "arch/i386/kernel/process.c",
because "kernel/process.c" will match the "*.c" specifier).

Also, while

	git-ls-files arch/i386/

will show all files under that subdirectory, doing the same without the
final slash would try to show the file "i386" under the "arch/"
subdirectory, and since there is no such file (even if there is such a
_directory_) it will not match anything at all.

These semantics may not seem intuitive, but they are actually very
practical. In particular, it makes it very simple to do

	git-ls-files fs/*.c | xargs grep some_pattern

and it does what you want.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>