- new applet diff. Rob Sullivan writes:

Here's my attempt at a mini diff applet - it's adapted from the code at
http://www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/diff/, and only supports
unified diffs.

I've busyboxified everything to a reasonable degree, so I think the code is
suitable enough to be included, but there's still a fair bit of cleaning up
to be done.

coreutils/Config.in

@@ -109,6 +109,38 @@ config CONFIG_DF
 	  df reports the amount of disk space used and available
 	  on filesystems.
 
+config CONFIG_DIFF
+	bool "diff"
+	default n
+	help
+	  diff compares two files or directories and outputs the
+	  differences between them in a form that can be given to
+	  the patch command.
+
+config CONFIG_FEATURE_DIFF_BINARY
+	bool "  Enable checks for binary files"
+	default y
+	depends on CONFIG_DIFF
+	help
+	  This option enables support for checking for binary files
+	  before a comparison is carried out.
+
+config CONFIG_FEATURE_DIFF_DIR
+	bool "  Enable directory support"
+	default y
+	depends on CONFIG_DIFF
+	help
+	  This option enables support for directory and subdirectory
+	  comparison.
+
+config CONFIG_FEATURE_DIFF_MINIMAL
+	bool "  Enable -d option to find smaller sets of changes"
+	default n
+	depends on CONFIG_DIFF
+	help
+	  Enabling this option allows the use of -d to make diff
+	  try hard to find the smallest possible set of changes.
+
 config CONFIG_DIRNAME
 	bool "dirname"
 	default n

coreutils/Makefile.in

@@ -25,6 +25,7 @@ COREUTILS-$(CONFIG_CUT)       += cut.o
 COREUTILS-$(CONFIG_DATE)      += date.o
 COREUTILS-$(CONFIG_DD)        += dd.o
 COREUTILS-$(CONFIG_DF)        += df.o
+COREUTILS-$(CONFIG_DIFF)      += diff.o
 COREUTILS-$(CONFIG_DIRNAME)   += dirname.o
 COREUTILS-$(CONFIG_DOS2UNIX)  += dos2unix.o
 COREUTILS-$(CONFIG_DU)        += du.o

include/applets.h

@@ -86,6 +86,7 @@ USE_DELGROUP(APPLET(delgroup, delgroup_main, _BB_DIR_BIN, _BB_SUID_NEVER))
 USE_DELUSER(APPLET(deluser, deluser_main, _BB_DIR_BIN, _BB_SUID_NEVER))
 USE_DEVFSD(APPLET(devfsd, devfsd_main, _BB_DIR_SBIN, _BB_SUID_NEVER))
 USE_DF(APPLET(df, df_main, _BB_DIR_BIN, _BB_SUID_NEVER))
+USE_DIFF(APPLET(diff, diff_main, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
 USE_DIRNAME(APPLET(dirname, dirname_main, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
 USE_DMESG(APPLET(dmesg, dmesg_main, _BB_DIR_BIN, _BB_SUID_NEVER))
 USE_DNSD(APPLET(dnsd, dnsd_main, _BB_DIR_USR_SBIN, _BB_SUID_ALWAYS))

include/usage.h

@@ -453,6 +453,26 @@
 	"Filesystem           1k-blocks      Used Available Use% Mounted on\n" \
 	"/dev/sda3              8690864   8553540    137324  98% /\n"
 
+#define diff_trivial_usage \
+	"[-abdiNqrTstw] [-S FILE] [-U LINES] FILE1 FILE2"
+#define diff_full_usage \
+	"Compare files line by line and output the differences between them.\n" \
+	"This diff implementation only supports unified diffs.\n\n" \
+	"Options:\n" \
+	"\t-a\tTreat all files as text\n" \
+	"\t-b\tIgnore changes in the amount of whitespace\n" \
+	"\t-d\tTry hard to find a smaller set of changes\n" \
+	"\t-i\tIgnore case differences\n" \
+	"\t-N\tTreat absent files as empty\n" \
+	"\t-q\tOutput only whether files differ\n" \
+	"\t-r\tRecursively compare any subdirectories\n" \
+	"\t-S\tStart with FILE when comparing directories\n" \
+	"\t-T\tMake tabs line up by prefixing a tab when necessary\n" \
+	"\t-s\tReport when two files are the same\n" \
+	"\t-t\tExpand tabs to spaces in output\n" \
+	"\t-U\tOutput LINES lines of context\n" \
+	"\t-w\tIgnore all whitespace\n"
+
 #define dirname_trivial_usage \
 	"FILENAME"
 #define dirname_full_usage \