commands: implement 'cmp' command

This command compares two files. It does not show the differences,
it only returns successfully if both files are identical and with
an error if they differ.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

commands/Kconfig

@@ -811,6 +811,16 @@ config CMD_CP
 	  Options:
 		  -v	verbose
 
+config CMD_CMP
+	tristate
+	prompt "cmp"
+	help
+	  compare two files
+
+	  Usage: cmp FILE1 FILE2
+
+	  Returns successfully if the two files are the same, return with an error if not
+
 config CMD_DIRNAME
 	tristate
 	prompt "dirname"

commands/Makefile

@@ -106,3 +106,4 @@ obj-$(CONFIG_CMD_IMD)		+= imd.o
 obj-$(CONFIG_CMD_HWCLOCK)	+= hwclock.o
 obj-$(CONFIG_CMD_USBGADGET)	+= usbgadget.o
 obj-$(CONFIG_CMD_FIRMWARELOAD)	+= firmwareload.o
+obj-$(CONFIG_CMD_CMP)		+= cmp.o

commands/cmp.c

@@ -0,0 +1,42 @@
+/*
+ * cmp - determine if two files differ
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <common.h>
+#include <command.h>
+#include <complete.h>
+#include <libfile.h>
+
+static int do_cmp(int argc, char *argv[])
+{
+	if (argc != 3)
+		return COMMAND_ERROR_USAGE;
+
+	return compare_file(argv[1], argv[2]);
+}
+
+BAREBOX_CMD_HELP_START(cmp)
+BAREBOX_CMD_HELP_TEXT("Returns successfully if the two files are the same, return with an error if not")
+BAREBOX_CMD_HELP_END
+
+BAREBOX_CMD_START(cmp)
+	.cmd		= do_cmp,
+	BAREBOX_CMD_DESC("compare two files")
+	BAREBOX_CMD_OPTS("FILE1 FILE2")
+	BAREBOX_CMD_GROUP(CMD_GRP_FILE)
+	BAREBOX_CMD_HELP(cmd_cmp_help)
+BAREBOX_CMD_END