maint: generate ChangeLog from git log

* Makefile.am (gen-ChangeLog): New rule.
(dist-hook): Depend on it.
(EXTRA_DIST): Distribute the two ChangeLog-* files.
* bootstrap.conf (gnulib_modules): Add gitlog-to-changelog.
(bootstrap_post_import_hook): Ensure that ChangeLog exists.
* build-aux/git-log-fix: New file.
* ChangeLog-2012: Renamed ...
* ChangeLog: ... from this.
* ChangeLog-1998: Renamed ...
* OChangeLog: ...from this
* .gitignore: Add ChangeLog.
(cherry picked from commit 5ef4a3c71c)

Conflicts:

	Makefile.am
	bootstrap.conf
	build-aux/.gitignore

bootstrap.conf

@@ -19,7 +19,8 @@
 gnulib_modules='
   announce-gen argmatch assert calloc-posix close config-h c-strcase
   configmake dirname error extensions fdl fopen-safer gendocs getopt-gnu
-  gettext git-version-gen gpl-3.0 hash inttypes isnan javacomp-script
+  gettext git-version-gen gitlog-to-changelog
+  gpl-3.0 hash inttypes isnan javacomp-script
   javaexec-script ldexpl maintainer-makefile malloc-gnu mbschr mbsrchr
   mbswidth obstack perror pipe-posix quote quotearg realloc-posix
   spawn-pipe stdbool stpcpy strdup-posix strerror strtoul strverscmp
@@ -60,6 +61,14 @@ excluded_files='
     m4/visibility.m4
 '
 
+gnulib_tool_option_extras='--symlink --makefile-name=gnulib.mk'
+
+bootstrap_post_import_hook()
+{
+  # Ensure that ChangeLog exists, for automake.
+  test -f ChangeLog || touch ChangeLog
+}
+
 bootstrap_epilogue()
 {
   # Make sure we don't need src/bison, which usually doesn't exist at