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.

.gitignore

@@ -1,4 +1,3 @@
-
 /*.cache
 /*.flc
 /*.prj
@@ -7,6 +6,7 @@
 /.version
 /ABOUT-NLS
 /COPYING
+/ChangeLog
 /GNUmakefile
 /INSTALL
 /Makefile
@@ -31,4 +31,3 @@
 /patches
 /releases
 /stamp-h*
-

Makefile.am

@@ -27,8 +27,7 @@ aclocaldir = @aclocaldir@
 aclocal_DATA = m4/bison-i18n.m4
 
 EXTRA_DIST = .prev-version .version \
-  cfg.mk \
+  cfg.mk ChangeLog-1998 ChangeLog-2012 PACKAGING
-  OChangeLog PACKAGING
 
 # Initialization before completion by local.mk's.
 AM_CFLAGS = $(WARN_CFLAGS)
@@ -62,7 +61,7 @@ include tests/local.mk
 BUILT_SOURCES += $(top_srcdir)/.version
 $(top_srcdir)/.version: configure
 	echo $(VERSION) > $@-t && mv $@-t $@
-dist-hook:
+dist-hook: gen-ChangeLog
 	echo $(VERSION) > $(distdir)/.tarball-version
 
 .PHONY: update-b4-copyright update-package-copyright-year
@@ -73,3 +72,15 @@ update-b4-copyright:
 	@echo 'warning: src/parse-gram.[hc] may need to be regenerated.'
 update-package-copyright-year:
 	$(build_aux)/$@ configure.ac
+
+gen_start_date = 2012-01-16
+.PHONY: gen-ChangeLog
+gen-ChangeLog:
+	$(AM_V_GEN)if test -d .git; then				\
+	  $(top_srcdir)/build-aux/gitlog-to-changelog			\
+	    --no-cluster						\
+	    --amend=$(srcdir)/build-aux/git-log-fix			\
+	    --since=$(gen_start_date) > $(distdir)/cl-t;		\
+	  rm -f $(distdir)/ChangeLog;					\
+	  mv $(distdir)/cl-t $(distdir)/ChangeLog;			\
+	fi

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
@@ -66,6 +67,9 @@ bootstrap_post_import_hook()
 {
   # Massage lib/gnulib.mk before using it later in the bootstrapping process.
   etc/prefix-gnulib-mk lib/$gnulib_mk
+
+  # Ensure that ChangeLog exists, for automake.
+  test -f ChangeLog || touch ChangeLog
 }
 
 bootstrap_epilogue()

build-aux/.gitignore

@@ -1,4 +1,3 @@
-
 /announce-gen
 /arg-nonnull.h
 /c++defs.h
@@ -9,6 +8,7 @@
 /depcomp
 /gendocs.sh
 /git-version-gen
+/gitlog-to-changelog
 /install-sh
 /javacomp.sh.in
 /javaexec.sh.in
@@ -21,4 +21,3 @@
 /vc-list-files
 /warn-on-use.h
 /ylwrap
-

build-aux/git-log-fix

@@ -0,0 +1,3 @@
+# This file is expected to be used via gitlog-to-changelog's --amend=FILE
+# option.  It specifies what changes to make to each given SHA1's commit
+# log and metadata, using Perl-eval'able expressions.