Index: gen_git_commit_h.sh
--- gen_git_commit_h.sh.orig
+++ gen_git_commit_h.sh
@@ -1,8 +1,7 @@
 #!/bin/sh
 cd $(dirname $0)
-commit=$(git rev-parse HEAD)
-git diff-index --quiet HEAD
-dirty=$?
+commit=${COMMIT}
+dirty=0
 printf "#pragma once\n#define GIT_COMMIT \"$commit\"\n#define GIT_DIRTY $dirty\n" > auto/git_info.h.new
 if cmp -s auto/git_info.h.new auto/git_info.h 2>&1 > /dev/null
 then