[gitg] Add --with-gtk option in the configure.ac. By default it is used gtk+ 2.

[Ignacio Casal Quinteiro <icq src gnome org>]

commit 4b2bbd9bd76f6ebf441fdc228c2a56a8e3447401
Author: Ignacio Casal Quinteiro <icq gnome org>
Date:   Thu Dec 30 15:07:32 2010 +0100

    Add --with-gtk option in the configure.ac. By default it is used gtk+ 2.

 configure.ac |   38 ++++++++++++++++++++++++++------------
 1 files changed, 26 insertions(+), 12 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 86cb61f..23bb98b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -51,18 +51,32 @@ AC_DEFINE_UNQUOTED(GETTEXT_PACKAGE,"$GETTEXT_PACKAGE", [Gettext package])
 
 AC_CHECK_LIB([m], [sinf])
 
-PKG_CHECK_EXISTS([gtk+-3.0 >= 2.90],
-		 [
-			GTK_REQUIRED=gtk+-3.0
-			GTK_REQUIRED_VERSION=2.90.0
-			GTKSOURCEVIEW_REQUIRED=gtksourceview-3.0
-			GTKSOURCEVIEW_REQUIRED_VERSION=2.90.0
-		 ],[
-			GTK_REQUIRED=gtk+-2.0
-			GTK_REQUIRED_VERSION=2.18.0
-			GTKSOURCEVIEW_REQUIRED=gtksourceview-2.0
-			GTKSOURCEVIEW_REQUIRED_VERSION=2.8.0
-		 ])
+# Which gtk+ API version to compile against
+
+AC_MSG_CHECKING([which gtk+ version to compile against])
+AC_ARG_WITH([gtk],
+	[AS_HELP_STRING([--with-gtk=2.0|3.0],[which gtk+ version to compile against (default: 2.0)])],
+	[case "$with_gtk" in
+		2.0|3.0) ;;
+		*) AC_MSG_ERROR([invalid gtk version specified]) ;;
+	esac],
+	[with_gtk=2.0])
+AC_MSG_RESULT([$with_gtk])
+
+case "$with_gtk" in
+	2.0)
+		GTK_REQUIRED=gtk+-2.0
+		GTK_REQUIRED_VERSION=2.18.0
+		GTKSOURCEVIEW_REQUIRED=gtksourceview-2.0
+		GTKSOURCEVIEW_REQUIRED_VERSION=2.8.0
+		;;
+	3.0)
+		GTK_REQUIRED=gtk+-3.0
+		GTK_REQUIRED_VERSION=2.90.0
+		GTKSOURCEVIEW_REQUIRED=gtksourceview-3.0
+		GTKSOURCEVIEW_REQUIRED_VERSION=2.90.0
+		;;
+esac
 
 GLIB_REQUIRED_VERSION=2.26