>From 5a07e65cd38fa949294e384fd5635408df4f2fab Mon Sep 17 00:00:00 2001
From: Bernhard Voelker <address@hidden>
Date: Thu, 13 Dec 2018 00:35:23 +0100
Subject: [PATCH] maintainer-makefile: provide make target to update gnulib to
 latest

* top/maint.mk (gnulib-sync, update-gnulib-to-latest): Add targets,
using the following hook variable to optionally e.g copy some files
from gnulib into the own package after pulling.
(_gl_GNULIB_SYNC_HOOK): Add hook variable to be
optionally overridden in 'cfg.mk'.  Default to ...
(_gl_GNULIB_SYNC_HOOK_empty): ... this empty target.
---
 ChangeLog    | 10 ++++++++++
 top/maint.mk | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index e3c929b52..313eb2a83 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2018-10-28  Bernhard Voelker  <address@hidden>
+
+	maintainer-makefile: provide make target to update gnulib to latest
+	* top/maint.mk (gnulib-sync, update-gnulib-to-latest): Add targets,
+	using the following hook variable to optionally e.g copy some files
+	from gnulib into the own package after pulling.
+	(_gl_GNULIB_SYNC_HOOK): Add hook variable to be
+	optionally overridden in 'cfg.mk'.  Default to ...
+	(_gl_GNULIB_SYNC_HOOK_empty): ... this empty target.
+
 2018-12-13  Bruno Haible  <address@hidden>
 
 	select tests: Avoid test failure on Cygwin.
diff --git a/top/maint.mk b/top/maint.mk
index 4889ebacc..b90a776dc 100644
--- a/top/maint.mk
+++ b/top/maint.mk
@@ -1571,6 +1571,42 @@ update-copyright:
 	  $$(export VC_LIST_EXCEPT_DEFAULT=COPYING && $(VC_LIST_EXCEPT)) \
 	  | $(update-copyright-env) xargs $(srcdir)/$(_build-aux)/$@
 
+# 'gnulib-sync': Update gnulib to latest.
+# Prerequisite: the working tree of both your package and gnulib are clean
+# (which is checked first).
+# To optionally copy some additional files from there right after the pull,
+# override the '_gl_GNULIB_SYNC_HOOK' make variable in your 'cfg.mk' with
+# the name of the make target which is then actually taking over the files.
+# This can be useful for files you need to have physically in your repository,
+# like e.g. 'COPYING' (for legal reasons) or 'bootstrap'.
+# Example:
+#   my_GNULIB_SYNC_HOOK:
+#   	@{ cd $(srcdir) \
+#   	    && cp gnulib/doc/COPYINGv3 COPYING \
+#   	    && cp gnulib/build-aux/bootstrap bootstrap \
+#   	; }
+#   export _gl_GNULIB_SYNC_HOOK = my_GNULIB_SYNC_HOOK
+#
+# Declare the default hook target (empty).
+.PHONY: _gl_GNULIB_SYNC_HOOK_empty
+_gl_GNULIB_SYNC_HOOK ?= _gl_GNULIB_SYNC_HOOK_empty
+_gl_GNULIB_SYNC_HOOK_empty:
+
+.PHONY: gnulib-sync update-gnulib-to-latest
+gnulib-sync update-gnulib-to-latest:
+	@{ cd $(srcdir) \
+	    && { printf 'gnulib: ' && git -C gnulib describe --always --dirty \
+		  && printf 'your package: ' && git describe --always --dirty \
+		  || echo dirty; \
+		  } | grep 'dirty$$' \
+			&& { echo "$@: error: tree is dirty" >&2; exit 1; } \
+			|| : \
+	    && set -x \
+	    && git -C gnulib pull origin master \
+	    && $(MAKE) $(_gl_GNULIB_SYNC_HOOK) \
+	    && git status --short --untracked-files=no \
+	; }
+
 # This tight_scope test is skipped with a warning if $(_gl_TS_headers) is not
 # overridden and $(_gl_TS_dir)/Makefile.am does not mention noinst_HEADERS.
 
-- 
2.19.2