Teach git diff about Objective-C syntax

Add support for recognition of Objective-C class & instance methods,
C functions, and class implementation/interfaces.
Signed-off-by: NJonathan del Strother <jon.delStrother@bestbefore.tv>
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>

Documentation/gitattributes.txt

@@ -315,6 +315,8 @@ patterns are available:
 
 - `java` suitable for source code in the Java language.
 
+- `objc` suitable for source code in the Objective-C language.
+
 - `pascal` suitable for source code in the Pascal/Delphi language.
 
 - `php` suitable for source code in the PHP language.

diff.c

@@ -1429,6 +1429,16 @@ static const struct funcname_pattern_entry builtin_funcname_pattern[] = {
 	  "!^[ \t]*(catch|do|for|if|instanceof|new|return|switch|throw|while)\n"
 	  "^[ \t]*(([ \t]*[A-Za-z_][A-Za-z_0-9]*){2,}[ \t]*\\([^;]*)$",
 	  REG_EXTENDED },
+	{ "objc",
+	  /* Negate C statements that can look like functions */
+	  "!^[ \t]*(do|for|if|else|return|switch|while)\n"
+	  /* Objective-C methods */
+	  "^[ \t]*([-+][ \t]*\\([ \t]*[A-Za-z_][A-Za-z_0-9* \t]*\\)[ \t]*[A-Za-z_].*)$\n"
+	  /* C functions */
+	  "^[ \t]*(([ \t]*[A-Za-z_][A-Za-z_0-9]*){2,}[ \t]*\\([^;]*)$\n"
+	  /* Objective-C class/protocol definitions */
+	  "^(@(implementation|interface|protocol)[ \t].*)$",
+	  REG_EXTENDED },
 	{ "pascal",
 	  "^((procedure|function|constructor|destructor|interface|"
 		"implementation|initialization|finalization)[ \t]*.*)$"