twrpme: add gitactivity changelog tag to device markdowns

Change-Id: I437a42c1b2ccd79b3f85ad0962c362680c28d171
diff --git a/_devices/samsunggalaxytab77.markdown b/_devices/samsunggalaxytab77.markdown
index 9629aa0..ce39bb8 100644
--- a/_devices/samsunggalaxytab77.markdown
+++ b/_devices/samsunggalaxytab77.markdown
@@ -5,6 +5,7 @@
 downloadfolder: degas
 oldurl: http://teamw.in/project/twrp2/108
 supportstatus: Current
+devicetree: https://github.com/TeamWin/android_device_samsung_degas.git
 maintainer: None
 oem: Samsung
 ---