t3508: add check_head_differs_from() helper function and use it

diff --git a/GIT-VERSION-GEN b/GIT-VERSION-GEN
index d4cb58e5df10d560cf7fe8680ca81ec217036b23..e45513dee938dde3a8428a833fb43023b04ca95b 100755 (executable)
--- a/GIT-VERSION-GEN
+++ b/GIT-VERSION-GEN
@@ -1,7 +1,7 @@
 #!/bin/sh
 
 GVF=GIT-VERSION-FILE
-DEF_VER=v1.7.1.1
+DEF_VER=v1.7.1.GIT
 
 LF='
 '