[gnome-boxes] Improve git diff output for vala files

[Christophe Fergeau <teuf src gnome org>]

commit a1c7ae28a3d3b6fb045761e682cbc24a4c1136ec
Author: Marc-Andrà Lureau <marcandre lureau gmail com>
Date:   Tue Jul 10 10:19:55 2012 +0200

    Improve git diff output for vala files
    
    Telling git that .vala files should be diff'ed as if they are
    java files makes the output more readable since the current method
    name appears in the hunk header. For some reason, using diff=csharp
    gives worse results than diff=java, that's why the latter is used.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=679666

 .gitattributes |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..ffaf68c
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1 @@
+*.vala   diff=java