From d7a0495000e35d06993605a9a31a5f9823292f8a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Carlos=20Mart=C3=ADn=20Nieto?= <cmn@dwim.me>
Date: Tue, 19 May 2015 14:56:01 +0200
Subject: [PATCH] Index: Add OpenIndex

This lets you persist an index at an arbitrary location.
---
 index.go      | 18 ++++++++++++++++++
 index_test.go | 24 ++++++++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/index.go b/index.go
index 009aeb6..2082ebd 100644
--- a/index.go
+++ b/index.go
@@ -96,6 +96,24 @@ func NewIndex() (*Index, error) {
 	return &Index{ptr: ptr}, nil
 }
 
+// OpenIndex creates a new index at the given path. If the file does
+// not exist it will be created when Write() is called.
+func OpenIndex(path string) (*Index, error) {
+	var ptr *C.git_index
+
+	var cpath = C.CString(path)
+	defer C.free(unsafe.Pointer(cpath))
+
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	if err := C.git_index_open(&ptr, cpath); err < 0 {
+		return nil, MakeGitError(err)
+	}
+
+	return &Index{ptr: ptr}, nil
+}
+
 // Add adds or replaces the given entry to the index, making a copy of
 // the data
 func (v *Index) Add(entry *IndexEntry) error {
diff --git a/index_test.go b/index_test.go
index a1f0c9c..9b54945 100644
--- a/index_test.go
+++ b/index_test.go
@@ -2,6 +2,7 @@ package git
 
 import (
 	"io/ioutil"
+	"os"
 	"runtime"
 	"testing"
 )
@@ -148,6 +149,29 @@ func TestIndexAddAllCallback(t *testing.T) {
 	}
 }
 
+func TestIndexOpen(t *testing.T) {
+	repo := createTestRepo(t)
+	defer cleanupTestRepo(t, repo)
+
+	path := repo.Workdir() + "/heyindex"
+
+	_, err := os.Stat(path)
+	if !os.IsNotExist(err) {
+		t.Fatal("new index file already exists")
+	}
+
+	idx, err := OpenIndex(path)
+	checkFatal(t, err)
+
+	err = idx.Write()
+	checkFatal(t, err)
+
+	_, err = os.Stat(path)
+	if os.IsNotExist(err) {
+		t.Fatal("new index file did not get written")
+	}
+}
+
 func checkFatal(t *testing.T, err error) {
 	if err == nil {
 		return