Move 'builtin-*' into a 'builtin/' subdirectory

This shrinks the top-level directory a bit, and makes it much more
pleasant to use auto-completion on the thing. Instead of

	[torvalds@nehalem git]$ em buil<tab>
	Display all 180 possibilities? (y or n)
	[torvalds@nehalem git]$ em builtin-sh
	builtin-shortlog.c     builtin-show-branch.c  builtin-show-ref.c
	builtin-shortlog.o     builtin-show-branch.o  builtin-show-ref.o
	[torvalds@nehalem git]$ em builtin-shor<tab>
	builtin-shortlog.c  builtin-shortlog.o
	[torvalds@nehalem git]$ em builtin-shortlog.c

you get

	[torvalds@nehalem git]$ em buil<tab>		[type]
	builtin/   builtin.h
	[torvalds@nehalem git]$ em builtin		[auto-completes to]
	[torvalds@nehalem git]$ em builtin/sh<tab>	[type]
	shortlog.c     shortlog.o     show-branch.c  show-branch.o  show-ref.c     show-ref.o
	[torvalds@nehalem git]$ em builtin/sho		[auto-completes to]
	[torvalds@nehalem git]$ em builtin/shor<tab>	[type]
	shortlog.c  shortlog.o
	[torvalds@nehalem git]$ em builtin/shortlog.c

which doesn't seem all that different, but not having that annoying
break in "Display all 180 possibilities?" is quite a relief.

NOTE! If you do this in a clean tree (no object files etc), or using an
editor that has auto-completion rules that ignores '*.o' files, you
won't see that annoying 'Display all 180 possibilities?' message - it
will just show the choices instead.  I think bash has some cut-off
around 100 choices or something.

So the reason I see this is that I'm using an odd editory, and thus
don't have the rules to cut down on auto-completion.  But you can
simulate that by using 'ls' instead, or something similar.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/unpack-file.c

@@ -0,0 +1,38 @@
+#include "cache.h"
+#include "blob.h"
+#include "exec_cmd.h"
+
+static char *create_temp_file(unsigned char *sha1)
+{
+	static char path[50];
+	void *buf;
+	enum object_type type;
+	unsigned long size;
+	int fd;
+
+	buf = read_sha1_file(sha1, &type, &size);
+	if (!buf || type != OBJ_BLOB)
+		die("unable to read blob object %s", sha1_to_hex(sha1));
+
+	strcpy(path, ".merge_file_XXXXXX");
+	fd = xmkstemp(path);
+	if (write_in_full(fd, buf, size) != size)
+		die_errno("unable to write temp-file");
+	close(fd);
+	return path;
+}
+
+int cmd_unpack_file(int argc, const char **argv, const char *prefix)
+{
+	unsigned char sha1[20];
+
+	if (argc != 2 || !strcmp(argv[1], "-h"))
+		usage("git unpack-file <sha1>");
+	if (get_sha1(argv[1], sha1))
+		die("Not a valid object name %s", argv[1]);
+
+	git_config(git_default_config, NULL);
+
+	puts(create_temp_file(sha1));
+	return 0;
+}