[GSoC][PATCH] userdiff: add built-in pattern for golang

[Alban Gruin <alban.gruin@gmail.com>]

This adds xfuncname and word_regex patterns for golang, a quite
popular programming language. It also includes test cases for the
xfuncname regex (t4018) and an updated documentation.

The xfuncname regex finds functions, structs and interfaces. The
word_regex pattern finds identifiers, integers, floats, complex
numbers and operators, according to the go specification.

Signed-off-by: Alban Gruin <alban.gruin@gmail.com>
---
 Documentation/gitattributes.txt | 2 ++
 t/t4018-diff-funcname.sh        | 1 +
 t/t4018/golang-complex-function | 8 ++++++++
 t/t4018/golang-func             | 4 ++++
 t/t4018/golang-interface        | 4 ++++
 t/t4018/golang-long-func        | 5 +++++
 t/t4018/golang-struct           | 4 ++++
 userdiff.c                      | 9 +++++++++
 8 files changed, 37 insertions(+)
 create mode 100644 t/t4018/golang-complex-function
 create mode 100644 t/t4018/golang-func
 create mode 100644 t/t4018/golang-interface
 create mode 100644 t/t4018/golang-long-func
 create mode 100644 t/t4018/golang-struct

diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt
index c21f5ca10..d52b254a2 100644
--- a/Documentation/gitattributes.txt
+++ b/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.
diff --git a/t/t4018-diff-funcname.sh b/t/t4018-diff-funcname.sh
index 1795ffc3a..22f9f88f0 100755
--- a/t/t4018-diff-funcname.sh
+++ b/t/t4018-diff-funcname.sh
@@ -33,6 +33,7 @@ diffpatterns="
 	css
 	fortran
 	fountain
+	golang
 	html
 	java
 	matlab
diff --git a/t/t4018/golang-complex-function b/t/t4018/golang-complex-function
new file mode 100644
index 000000000..a9211ed18
--- /dev/null
+++ b/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
+}
diff --git a/t/t4018/golang-func b/t/t4018/golang-func
new file mode 100644
index 000000000..b17698218
--- /dev/null
+++ b/t/t4018/golang-func
@@ -0,0 +1,4 @@
+func RIGHT() {
+	a := 5
+        b := ChangeMe
+}
diff --git a/t/t4018/golang-interface b/t/t4018/golang-interface
new file mode 100644
index 000000000..2e03d4fc0
--- /dev/null
+++ b/t/t4018/golang-interface
@@ -0,0 +1,4 @@
+type RIGHT interface {
+	a() Type
+        b() ChangeMe
+}
diff --git a/t/t4018/golang-long-func b/t/t4018/golang-long-func
new file mode 100644
index 000000000..ac3a77b5c
--- /dev/null
+++ b/t/t4018/golang-long-func
@@ -0,0 +1,5 @@
+func RIGHT(aVeryVeryVeryLongVariableName AVeryVeryVeryLongType,
+	anotherLongVariableName AnotherLongType) {
+	a := 5
+	b := ChangeMe
+}
diff --git a/t/t4018/golang-struct b/t/t4018/golang-struct
new file mode 100644
index 000000000..5cd70c8dc
--- /dev/null
+++ b/t/t4018/golang-struct
@@ -0,0 +1,4 @@
+type RIGHT struct {
+	a Type
+        b ChangeMe
+}
diff --git a/userdiff.c b/userdiff.c
index dbfb4e13c..8f5028f6b 100644
--- a/userdiff.c
+++ b/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",
-- 
2.16.1