+.PHONY: ChangeLog change-history change-history-commit
+.PHONY: master-branch-is-current no-ChangeLog unchanged-history-files
+
+# The newest revision that should not appear in the generated ChangeLog.
+gen_origin = 2c1b8604946efbcd8ec5dd6c6dda7541ce4fc3c0
+
+# Convert git commit log to ChangeLog file. make-dist uses this.
+ChangeLog:
+ $(AM_V_GEN)distprefix=$(distprefix) srcprefix=$(srcdir)/ \
+ $(srcdir)/build-aux/gitlog-to-emacslog $(gen_origin)
+
+# The ChangeLog history files are called ChangeLog.1, ChangeLog.2, ...,
+# ChangeLog.$(CHANGELOG_HISTORY_INDEX_MAX). $(CHANGELOG_N) stands for
+# the newest (highest-numbered) ChangeLog history file.
+CHANGELOG_HISTORY_INDEX_MAX = 2
+CHANGELOG_N = ChangeLog.$(CHANGELOG_HISTORY_INDEX_MAX)
+
+# Check that we are in a good state for changing history.
+no-ChangeLog:
+ test ! -f ChangeLog
+master-branch-is-current:
+ git branch | grep -q '^\* master$$'
+unchanged-history-files:
+ x=$$(git diff-files --name-only $(CHANGELOG_N) Makefile.in) && \
+ test -z "$$x"
+
+# Copy newer commit messages to the start of the ChangeLog history file,
+# and consider them to be older.
+change-history: no-ChangeLog master-branch-is-current unchanged-history-files \
+ ChangeLog
+ (sed '/^;; [L]ocal Variables:/,$$d' <ChangeLog && cat $(CHANGELOG_N)) \
+ >$(CHANGELOG_N).tmp
+ new_origin=$$(git log --pretty=format:%H HEAD^!) && \
+ sed 's/^\(gen_origin *= *\).*/\1'"$$new_origin/" \
+ <Makefile.in >Makefile.in.tmp
+ mv $(CHANGELOG_N).tmp $(CHANGELOG_N)
+ mv Makefile.in.tmp Makefile.in
+ $(MAKE) $@-commit
+
+# If 'make change-history' fails because the newest ChangeLog history
+# file contains invalid text, fix the file by hand and then run
+# 'make change-history-commit'.
+change-history-commit:
+ git commit -m'; make $@' $(CHANGELOG_N) Makefile.in
+