Merge branch 'ag/userdiff-go-funcname'

"git diff" and friends learned funcname patterns for Go language
source files.

* ag/userdiff-go-funcname:
  userdiff: add built-in pattern for golang

Documentation/gitattributes.txt

@@ -714,6 +714,8 @@ patterns are available:
 
 - `fountain` suitable for Fountain documents.
 
+- `golang` suitable for source code in the Go language.
+
 - `html` suitable for HTML/XHTML documents.
 
 - `java` suitable for source code in the Java language.

t/t4018-diff-funcname.sh

@@ -33,6 +33,7 @@ diffpatterns="
 	css
 	fortran
 	fountain
+	golang
 	html
 	java
 	matlab

t/t4018/golang-complex-function

@@ -0,0 +1,8 @@
+type Test struct {
+	a Type
+}
+
+func (t *Test) RIGHT(a Type) (Type, error) {
+	t.a = a
+	return ChangeMe, nil
+}

t/t4018/golang-func

@@ -0,0 +1,4 @@
+func RIGHT() {
+	a := 5
+	b := ChangeMe
+}

t/t4018/golang-interface

@@ -0,0 +1,4 @@
+type RIGHT interface {
+	a() Type
+	b() ChangeMe
+}

t/t4018/golang-long-func

@@ -0,0 +1,5 @@
+func RIGHT(aVeryVeryVeryLongVariableName AVeryVeryVeryLongType,
+	anotherLongVariableName AnotherLongType) {
+	a := 5
+	b := ChangeMe
+}

t/t4018/golang-struct

@@ -0,0 +1,4 @@
+type RIGHT struct {
+	a Type
+	b ChangeMe
+}

userdiff.c

@@ -38,6 +38,15 @@ IPATTERN("fortran",
 	 "|//|\\*\\*|::|[/<>=]="),
 IPATTERN("fountain", "^((\\.[^.]|(int|ext|est|int\\.?/ext|i/e)[. ]).*)$",
 	 "[^ \t-]+"),
+PATTERNS("golang",
+	 /* Functions */
+	 "^[ \t]*(func[ \t]*.*(\\{[ \t]*)?)\n"
+	 /* Structs and interfaces */
+	 "^[ \t]*(type[ \t].*(struct|interface)[ \t]*(\\{[ \t]*)?)",
+	 /* -- */
+	 "[a-zA-Z_][a-zA-Z0-9_]*"
+	 "|[-+0-9.eE]+i?|0[xX]?[0-9a-fA-F]+i?"
+	 "|[-+*/<>%&^|=!:]=|--|\\+\\+|<<=?|>>=?|&\\^=?|&&|\\|\\||<-|\\.{3}"),
 PATTERNS("html", "^[ \t]*(<[Hh][1-6]([ \t].*)?>.*)$",
 	 "[^<>= \t]+"),
 PATTERNS("java",