[beast: 8/24] BUILD: Makefile.decl: provide GITSTAMPS for dependecy checking

[Tim Janik <timj src gnome org>]

commit 9748295f8fa8614d4bf24298994166bb38a332d5
Author: Tim Janik <timj gnu org>
Date:   Mon Sep 14 09:44:10 2015 +0200

    BUILD: Makefile.decl: provide GITSTAMPS for dependecy checking

 Makefile.decl |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/Makefile.decl b/Makefile.decl
index 14d0cf7..5929702 100644
--- a/Makefile.decl
+++ b/Makefile.decl
@@ -21,6 +21,12 @@ QSTDERR = $(Q:@=2>/dev/null)
 AM_CFLAGS   += -D_BIRNET_SOURCE_EXTENSIONS
 AM_CXXFLAGS += -D_BIRNET_SOURCE_EXTENSIONS
 
+# == GITSTAMPS ==
+# list of stamp files touched by commits
+GITSTAMPS = $(shell test -e "$${GIT_DIR:-.git}" && \
+               ls 2>/dev/null "$${GIT_DIR:-.git}/`git symbolic-ref -q HEAD || \
+               echo HEAD`" "$${GIT_DIR:-.git}/packed-refs" "$${GIT_DIR:-.git}/HEAD")
+
 # == download ==
 # recursive rule supported by all Makefiles to download files hosted online
 .PHONY: download download-recursive download-local