[network-manager-pptp] build: use GIT_SHA_RECORD(NM_GIT_SHA) macro from "m4/git-sha-record.m4"

[Thomas Haller <thaller src gnome org>]

commit 78782c5db56677b88abba984b80d4a1bf5e2d9cc
Author: Thomas Haller <thaller redhat com>
Date:   Wed Sep 14 14:20:13 2016 +0200

    build: use GIT_SHA_RECORD(NM_GIT_SHA) macro from "m4/git-sha-record.m4"
    
    See 
https://cgit.freedesktop.org/NetworkManager/NetworkManager/commit/?id=b33aacbc91864f20f4733919af1a4cf8f725ca94

 configure.ac         |    2 ++
 m4/git-sha-record.m4 |   15 +++++++++++++++
 2 files changed, 17 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index cfe9a6a..e3d58fb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -51,6 +51,8 @@ AC_PROG_GCC_TRADITIONAL
 AC_FUNC_MEMCMP
 AC_CHECK_FUNCS(select socket uname)
 
+GIT_SHA_RECORD(NM_GIT_SHA)
+
 AC_SEARCH_LIBS([dlopen], [dl dld], [], [ac_cv_search_dlopen=])
 AC_SUBST([DL_LIBS], "$ac_cv_search_dlopen")
 
diff --git a/m4/git-sha-record.m4 b/m4/git-sha-record.m4
new file mode 100644
index 0000000..e259b39
--- /dev/null
+++ b/m4/git-sha-record.m4
@@ -0,0 +1,15 @@
+dnl GIT_SHA_RECORD($1, $2)
+dnl
+dnl $1: the name of the assigned variable. For example NM_GIT_SHA,
+dnl     NMA_GIT_SHA, LIBNL_GIT_SHA.
+dnl $2: by default, a define to config.h is added. This can be
+dnl     suppressed by passing "no-config-h".
+dnl
+AC_DEFUN([GIT_SHA_RECORD], [
+    m4_define([git_sha_record_v],
+              [m4_esyscmd([ ( [ -d ./.git/ ] && [ "$(readlink -f ./.git/)" = "$(readlink -f "$(git rev-parse 
--git-dir 2>/dev/null)" 2>/dev/null)" ] && git rev-parse --verify -q HEAD 2>/dev/null ) || true ])])
+$1=git_sha_record_v
+if test ""$2"" != "no-config-h" ; then
+    AC_DEFINE_UNQUOTED($1,"$$1",[git commit id of the original source code version])
+fi
+])