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/merge-file.c

@@ -0,0 +1,96 @@
+#include "builtin.h"
+#include "cache.h"
+#include "xdiff/xdiff.h"
+#include "xdiff-interface.h"
+#include "parse-options.h"
+
+static const char *const merge_file_usage[] = {
+	"git merge-file [options] [-L name1 [-L orig [-L name2]]] file1 orig_file file2",
+	NULL
+};
+
+static int label_cb(const struct option *opt, const char *arg, int unset)
+{
+	static int label_count = 0;
+	const char **names = (const char **)opt->value;
+
+	if (label_count >= 3)
+		return error("too many labels on the command line");
+	names[label_count++] = arg;
+	return 0;
+}
+
+int cmd_merge_file(int argc, const char **argv, const char *prefix)
+{
+	const char *names[3] = { NULL, NULL, NULL };
+	mmfile_t mmfs[3];
+	mmbuffer_t result = {NULL, 0};
+	xmparam_t xmp = {{XDF_NEED_MINIMAL}};
+	int ret = 0, i = 0, to_stdout = 0;
+	int level = XDL_MERGE_ZEALOUS_ALNUM;
+	int style = 0, quiet = 0;
+	int favor = 0;
+	int nongit;
+
+	struct option options[] = {
+		OPT_BOOLEAN('p', "stdout", &to_stdout, "send results to standard output"),
+		OPT_SET_INT(0, "diff3", &style, "use a diff3 based merge", XDL_MERGE_DIFF3),
+		OPT_SET_INT(0, "ours", &favor, "for conflicts, use our version",
+			    XDL_MERGE_FAVOR_OURS),
+		OPT_SET_INT(0, "theirs", &favor, "for conflicts, use their version",
+			    XDL_MERGE_FAVOR_THEIRS),
+		OPT__QUIET(&quiet),
+		OPT_CALLBACK('L', NULL, names, "name",
+			     "set labels for file1/orig_file/file2", &label_cb),
+		OPT_END(),
+	};
+
+	prefix = setup_git_directory_gently(&nongit);
+	if (!nongit) {
+		/* Read the configuration file */
+		git_config(git_xmerge_config, NULL);
+		if (0 <= git_xmerge_style)
+			style = git_xmerge_style;
+	}
+
+	argc = parse_options(argc, argv, prefix, options, merge_file_usage, 0);
+	if (argc != 3)
+		usage_with_options(merge_file_usage, options);
+	if (quiet) {
+		if (!freopen("/dev/null", "w", stderr))
+			return error("failed to redirect stderr to /dev/null: "
+				     "%s\n", strerror(errno));
+	}
+
+	for (i = 0; i < 3; i++) {
+		if (!names[i])
+			names[i] = argv[i];
+		if (read_mmfile(mmfs + i, argv[i]))
+			return -1;
+		if (buffer_is_binary(mmfs[i].ptr, mmfs[i].size))
+			return error("Cannot merge binary files: %s\n",
+					argv[i]);
+	}
+
+	ret = xdl_merge(mmfs + 1, mmfs + 0, names[0], mmfs + 2, names[2],
+			&xmp, XDL_MERGE_FLAGS(level, style, favor), &result);
+
+	for (i = 0; i < 3; i++)
+		free(mmfs[i].ptr);
+
+	if (ret >= 0) {
+		const char *filename = argv[0];
+		FILE *f = to_stdout ? stdout : fopen(filename, "wb");
+
+		if (!f)
+			ret = error("Could not open %s for writing", filename);
+		else if (result.size &&
+			 fwrite(result.ptr, result.size, 1, f) != 1)
+			ret = error("Could not write to %s", filename);
+		else if (fclose(f))
+			ret = error("Could not close %s", filename);
+		free(result.ptr);
+	}
+
+	return ret;
+}