gitk: Add emacs editor variable block

Help contributors use the correct indentation style.
Signed-off-by: NPat Thoyts <patthoyts@users.sourceforge.net>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

gitk

@@ -11610,3 +11610,9 @@ if {[tk windowingsystem] eq "win32"} {
 }
 
 getcommits {}
+
+# Local variables:
+# mode: tcl
+# indent-tabs-mode: t
+# tab-width: 8
+# End: