utils/diffconfig: add diffconfig utility

Diffconfig is a simple utility for comparing two configuration files.
See usage in the script for more info.

Borrowed from the Linux kernel source code and adapted to Buildroot.

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

DEVELOPERS

@@ -1014,6 +1014,9 @@ F:	package/turbolua/
 N:	Marcin Nowakowski <marcin.nowakowski@imgtec.com>
 F:	package/libkcapi/
 
+N:	Marcus Folkesson <marcus.folkesson@gmail.com>
+F:	utils/diffconfig
+
 N:	Marek Belisko <marek.belisko@open-nandra.com>
 F:	package/libatasmart/
 F:	package/polkit/

utils/diffconfig

@@ -0,0 +1,136 @@
+#!/usr/bin/python
+#
+# diffconfig - a tool to compare .config files.
+#
+# originally written in 2006 by Matt Mackall
+#  (at least, this was in his bloatwatch source code)
+# last worked on 2008 by Tim Bird for the Linux kernel
+# Adapted to Buildroot 2017 by Marcus Folkesson
+#
+
+import sys, os
+
+def usage():
+    print("""Usage: diffconfig [-h] [-m] [<config1> <config2>]
+
+Diffconfig is a simple utility for comparing two .config files.
+Using standard diff to compare .config files often includes extraneous and
+distracting information.  This utility produces sorted output with only the
+changes in configuration values between the two files.
+
+Added and removed items are shown with a leading plus or minus, respectively.
+Changed items show the old and new values on a single line.
+
+If -m is specified, then output will be in "merge" style, which has the
+changed and new values in kernel config option format.
+
+If no config files are specified, .config and .config.old are used.
+
+Example usage:
+ $ diffconfig .config config-with-some-changes
+-LINUX_KERNEL_INTREE_DTS_NAME "vexpress-v2p-ca9"
+ LINUX_KERNEL_DTS_SUPPORT y -> n
+ LINUX_KERNEL_USE_INTREE_DTS y -> n
+ PACKAGE_DFU_UTIL n -> y
+ PACKAGE_LIBUSB n -> y
+ TARGET_GENERIC_HOSTNAME "buildroot" -> "Tuxie"
+ TARGET_GENERIC_ISSUE "Welcome to Buildroot" -> "Welcome to CustomBoard"
++PACKAGE_LIBUSB_COMPAT n
+
+""")
+    sys.exit(0)
+
+# returns a dictionary of name/value pairs for config items in the file
+def readconfig(config_file):
+    d = {}
+    for line in config_file:
+        line = line[:-1]
+        if line[:4] == "BR2_":
+            name, val = line[4:].split("=", 1)
+            d[name] = val
+        if line[-11:] == " is not set":
+            d[line[6:-11]] = "n"
+    return d
+
+def print_config(op, config, value, new_value):
+    global merge_style
+
+    if merge_style:
+        if new_value:
+            if new_value=="n":
+                print("# BR2_%s is not set" % config)
+            else:
+                print("BR2_%s=%s" % (config, new_value))
+    else:
+        if op=="-":
+            print("-%s %s" % (config, value))
+        elif op=="+":
+            print("+%s %s" % (config, new_value))
+        else:
+            print(" %s %s -> %s" % (config, value, new_value))
+
+def main():
+    global merge_style
+
+    # parse command line args
+    if ("-h" in sys.argv or "--help" in sys.argv):
+        usage()
+
+    merge_style = 0
+    if "-m" in sys.argv:
+        merge_style = 1
+        sys.argv.remove("-m")
+
+    argc = len(sys.argv)
+    if not (argc==1 or argc == 3):
+        print("Error: incorrect number of arguments or unrecognized option")
+        usage()
+
+    if argc == 1:
+        # if no filenames given, assume .config and .config.old
+        build_dir=""
+        if "KBUILD_OUTPUT" in os.environ:
+            build_dir = os.environ["KBUILD_OUTPUT"]+"/"
+        configa_filename = build_dir + ".config.old"
+        configb_filename = build_dir + ".config"
+    else:
+        configa_filename = sys.argv[1]
+        configb_filename = sys.argv[2]
+
+    try:
+        a = readconfig(open(configa_filename))
+        b = readconfig(open(configb_filename))
+    except (IOError):
+        e = sys.exc_info()[1]
+        print("I/O error[%s]: %s\n" % (e.args[0],e.args[1]))
+        usage()
+
+    # print items in a but not b (accumulate, sort and print)
+    old = []
+    for config in a:
+        if config not in b:
+            old.append(config)
+    old.sort()
+    for config in old:
+        print_config("-", config, a[config], None)
+        del a[config]
+
+    # print items that changed (accumulate, sort, and print)
+    changed = []
+    for config in a:
+        if a[config] != b[config]:
+            changed.append(config)
+        else:
+            del b[config]
+    changed.sort()
+    for config in changed:
+        print_config("->", config, a[config], b[config])
+        del b[config]
+
+    # now print items in b but not in a
+    # (items from b that were in a were removed above)
+    new = sorted(b.keys())
+    for config in new:
+        print_config("+", config, None, b[config])
+
+main()