[gtkglext] Added make rule to generate ChangeLog from git.

[Braden McDaniel <bradenmcd src gnome org>]

commit 0631da0a8eabbc0eae6811451315887db822a2a1
Author: Braden McDaniel <braden bolt endoframe net>
Date:   Sat Dec 19 23:36:10 2009 -0500

    Added make rule to generate ChangeLog from git.

 .gitignore                     |    1 +
 ChangeLog => ChangeLog.pre-1-2 |    0
 Makefile.am                    |   20 +++++++++++++++-----
 3 files changed, 16 insertions(+), 5 deletions(-)
---
diff --git a/.gitignore b/.gitignore
index fa191f8..0a89b86 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,6 +9,7 @@
 .libs
 ABOUT-NLS
 AUTHORS
+ChangeLog
 INSTALL
 Makefile
 Makefile.in
diff --git a/ChangeLog b/ChangeLog.pre-1-2
similarity index 100%
rename from ChangeLog
rename to ChangeLog.pre-1-2
diff --git a/Makefile.am b/Makefile.am
index 475498b..92d4d2a 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -10,6 +10,7 @@ ACLOCAL_AMFLAGS = -I m4macros
 EXTRA_DIST = \
 	README.win32			\
 	ChangeLog.pre-1-0		\
+	ChangeLog.pre-1-2		\
 	gdkglext.pc.in			\
 	gtkglext.pc.in			\
 	gdkglext-uninstalled.pc.in	\
@@ -64,7 +65,7 @@ DISTCLEANFILES = \
 	gtkglext-$(GDK_TARGET)-$(API_VER)-uninstalled.pc	\
 	gtkglext-$(API_VER)-uninstalled.pc
 
-.PHONY: examples clean-examples
+.PHONY: examples clean-examples ChangeLog
 
 examples: all
 	( cd $(top_builddir)/examples && $(MAKE) $(MFLAGS) )
@@ -72,7 +73,16 @@ examples: all
 clean-examples:
 	( cd $(top_builddir)/examples && $(MAKE) $(MFLAGS) clean )
 
-.PHONY: changelog
-changelog:
-	cvs2cl -b -t --hide-filenames
-
+ChangeLog:
+	@echo Creating $@
+	@if test -d "$(srcdir)/.git"; then \
+	  (GIT_DIR=$(top_srcdir)/.git $(top_srcdir)/missing --run git log --stat) | fmt --split-only > $  tmp \
+	  && mv -f $  tmp $@ \
+	  || ($(RM) $  tmp; \
+	      echo Failed to generate ChangeLog, your ChangeLog may be outdated >&2; \
+	      (test -f $@ || echo git-log is required to generate this file >> $@)); \
+	else \
+	  test -f $@ || \
+	  (echo A git checkout and git-log is required to generate ChangeLog >&2 && \
+	  echo A git checkout and git-log is required to generate this file >> $@); \
+	fi