userdiff: add builtin diff driver for kotlin language.

The xfuncname pattern finds func/class declarations
in diffs to display as a hunk header. The word_regex
pattern finds individual tokens in Kotlin code to generate
appropriate diffs.

This patch adds xfuncname regex and word_regex for Kotlin
language.

Signed-off-by: Jaydeep P Das <[email protected]>
Acked-by: Johannes Sixt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: JDeepD

Documentation/gitattributes.txt

@@ -829,6 +829,8 @@ patterns are available:
 
 - `java` suitable for source code in the Java language.
 
+- `kotlin` suitable for source code in the Kotlin language.
+
 - `markdown` suitable for Markdown documents.
 
 - `matlab` suitable for source code in the MATLAB and Octave languages.

t/t4018/kotlin-class

@@ -0,0 +1,5 @@
+class RIGHT {
+	//comment
+	//comment
+	return ChangeMe
+}

t/t4018/kotlin-enum-class

@@ -0,0 +1,5 @@
+enum class RIGHT{
+	// Left
+	// a comment
+	ChangeMe
+}

t/t4018/kotlin-fun

@@ -0,0 +1,5 @@
+fun RIGHT(){
+	//a comment
+	//b comment
+    return ChangeMe()
+}

t/t4018/kotlin-inheritace-class

@@ -0,0 +1,5 @@
+open class RIGHT{
+	// a comment
+	// b comment
+	// ChangeMe
+}

t/t4018/kotlin-inline-class

@@ -0,0 +1,5 @@
+value class RIGHT(Args){
+	// a comment
+	// b comment
+	ChangeMe
+}

t/t4018/kotlin-interface

@@ -0,0 +1,5 @@
+interface RIGHT{
+	//another comment
+	//another comment
+	//ChangeMe
+}

t/t4018/kotlin-nested-fun

@@ -0,0 +1,9 @@
+class LEFT{
+	class CENTER{
+		fun RIGHT(  a:Int){
+			//comment
+			//comment
+			ChangeMe
+		}
+	}
+}

t/t4018/kotlin-public-class

@@ -0,0 +1,5 @@
+public class RIGHT{
+	//comment1
+	//comment2
+	ChangeMe
+}

t/t4018/kotlin-sealed-class

@@ -0,0 +1,5 @@
+sealed class RIGHT {
+	// a comment
+	// b comment
+	ChangeMe
+}