From fc6eaf36388841b16ff004e1d48e887d3f9613dc Mon Sep 17 00:00:00 2001
From: michael boulton <61595820+mbfr@users.noreply.github.com>
Date: Fri, 14 Aug 2020 19:19:21 +0100
Subject: [PATCH] Fix null pointer dereference in status.ByIndex (#628)

`git_status_byindex` can return a null pointer if there is no statuses.
---
 status.go      |  4 ++++
 status_test.go | 28 ++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/status.go b/status.go
index e37a96d..3923e1a 100644
--- a/status.go
+++ b/status.go
@@ -6,6 +6,7 @@ package git
 import "C"
 
 import (
+	"errors"
 	"runtime"
 	"unsafe"
 )
@@ -86,6 +87,9 @@ func (statusList *StatusList) ByIndex(index int) (StatusEntry, error) {
 		return StatusEntry{}, ErrInvalid
 	}
 	ptr := C.git_status_byindex(statusList.ptr, C.size_t(index))
+	if ptr == nil {
+		return StatusEntry{}, errors.New("index out of Bounds")
+	}
 	entry := statusEntryFromC(ptr)
 	runtime.KeepAlive(statusList)
 
diff --git a/status_test.go b/status_test.go
index 17ed94f..d5cd530 100644
--- a/status_test.go
+++ b/status_test.go
@@ -61,3 +61,31 @@ func TestStatusList(t *testing.T) {
 		t.Fatal("Incorrect entry path: ", entry.IndexToWorkdir.NewFile.Path)
 	}
 }
+
+func TestStatusNothing(t *testing.T) {
+	t.Parallel()
+	repo := createTestRepo(t)
+	defer cleanupTestRepo(t, repo)
+
+	seedTestRepo(t, repo)
+
+	opts := &StatusOptions{
+		Show:  StatusShowIndexAndWorkdir,
+		Flags: StatusOptIncludeUntracked | StatusOptRenamesHeadToIndex | StatusOptSortCaseSensitively,
+	}
+
+	statusList, err := repo.StatusList(opts)
+	checkFatal(t, err)
+
+	entryCount, err := statusList.EntryCount()
+	checkFatal(t, err)
+
+	if entryCount != 0 {
+		t.Fatal("expected no statuses in empty repo")
+	}
+
+	_, err = statusList.ByIndex(0)
+	if err == nil {
+		t.Error("expected error getting status by index")
+	}
+}