mesa/bin/extract_git_sha1

#!/bin/sh
touch src/mesa/main/git_sha1.h
if which git > /dev/null; then
    # Extract the 7-digit "short" SHA1 for the current HEAD, convert
    # it to a string, and wrap it in a #define.  This is used in
    # src/mesa/main/version.c to put the GIT SHA1 in the GL_VERSION string.
    git log -n 1 --oneline |\
	sed 's/^\([^ ]*\) .*/#define MESA_GIT_SHA1 "git-\1"/' \
	> src/mesa/main/git_sha1.h
fi