Replace static ChangeLog with dist-hook to generate from git log

ChangeLog

-2006-02-13  Adam Jackson  <ajax@freedesktop.org>
-
-	* src/screen.c:
-	Minimal hack to enable EXT_texture_from_pixmap.
-
-2006-01-18  Adam Jackson  <ajax@freedesktop.org>
-
-	* include/comp.h:
-	* src/screen.c:
-	* src/texture.c:
-	Allow using EXT_texture_from_drawable as well as MESA_render_texture.
-
-	* src/screen.c:
-	Also check for EXT_tfd in the GLX extension string.
-
-	* plugins/Makefile.am:
-	Deconfuse automake.
-
-2005-12-31  Zack Rusin  <zack@freedesktop.org>
-
-	Initial import.  (David Reveman)

Makefile.am

@@ -6,3 +6,13 @@ EXTRA_DIST =	      \
 
 pkgconfigdir = $(libdir)/pkgconfig
 pkgconfig_DATA = glxcomp.pc
+
+EXTRA_DIST += ChangeLog
+MAINTAINERCLEANFILES = ChangeLog
+
+.PHONY: ChangeLog
+
+ChangeLog:
+	(GIT_DIR=$(top_srcdir)/.git git-log > .changelog.tmp && mv .changelog.tmp ChangeLog; rm -f .changelog.tmp) || (touch ChangeLog; echo 'git directory not found: installing possibly empty changelog.' >&2)
+
+dist-hook: ChangeLog