[gnome-directory-thumbnailer] build: Use AX_GENERATE_CHANGELOG to generate the ChangeLog

[Philip Withnall <pwithnall src gnome org>]

commit 983b90bbbbd6de147b182aad531941b236051a21
Author: Philip Withnall <philip withnall collabora co uk>
Date:   Tue Jun 9 13:27:36 2015 +0100

    build: Use AX_GENERATE_CHANGELOG to generate the ChangeLog
    
    http://www.gnu.org/software/autoconf-archive/ax_generate_changelog.html

 ChangeLog    |    2 ++
 Makefile.am  |   20 ++------------------
 configure.ac |    1 +
 3 files changed, 5 insertions(+), 18 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
new file mode 100644
index 0000000..92bcb9b
--- /dev/null
+++ b/ChangeLog
@@ -0,0 +1,2 @@
+The ChangeLog is auto-generated when releasing.
+If you are seeing this, use 'git log' for a detailed list of changes.
diff --git a/Makefile.am b/Makefile.am
index ba4c4de..1800f0c 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -67,23 +67,7 @@ MAINTAINERCLEANFILES += \
        $(NULL)
 
 # ChangeLog
-ChangeLog: $(srcdir)/ChangeLog
-$(srcdir)/ChangeLog:
-       @echo Creating $@
-       @if test -d "$(srcdir)/.git"; then \
-         (GIT_DIR=$(top_srcdir)/.git ./build-aux/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-             echo Failed to generate ChangeLog, your ChangeLog may be outdated 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
-.PHONY: $(srcdir)/ChangeLog
-
-MAINTAINERCLEANFILES += ChangeLog
+ GENERATE_CHANGELOG_RULES@
+dist-hook: dist-ChangeLog
 
 -include $(top_srcdir)/git.mk
diff --git a/configure.ac b/configure.ac
index 6e26c38..450e94c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -49,6 +49,7 @@ IT_PROG_INTLTOOL([0.40.0])
 GNOME_DEBUG_CHECK
 GNOME_COMPILE_WARNINGS([maximum])
 GNOME_MAINTAINER_MODE_DEFINES
+AX_GENERATE_CHANGELOG
 
 AC_SUBST([AM_CPPFLAGS])
 AC_SUBST([AM_CFLAGS])