From 8f84fef2ebe0d957c30ed162a76ef605d2a11518 Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyering@redhat.com>
Date: Wed, 15 Jul 2009 09:54:26 +0200
Subject: [PATCH] build: submodule machinery now works also when no tag is
 reachable

The code in cfg.mk to detect when the git submodule was out of date
worked most of the time, but not when checked out in a certain way.
* cfg.mk: Extract submodule hash from command output and file,
and compare only that, since the format of the full line may vary.
Reported by Mike Burns, with some diagnosis by Daniel P Berrange.
---
 cfg.mk | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/cfg.mk b/cfg.mk
index 0bf935d51a..64bd26e0ff 100644
--- a/cfg.mk
+++ b/cfg.mk
@@ -242,9 +242,17 @@ prev_version_file = /dev/null
 
 ifeq (0,$(MAKELEVEL))
   _curr_status = .git-module-status
-  _update_required :=							\
-    $(shell t=$$(git submodule status);					\
-      test "$$t" = "$$(cat $(_curr_status) 2>/dev/null)"; echo $$?)
+  # The sed filter accommodates those who check out on a commit from which
+  # no tag is reachable.  In that case, git submodule status prints a "-"
+  # in column 1 and does not print a "git describe"-style string after the
+  # submodule name.  Contrast these:
+  # -b653eda3ac4864de205419d9f41eec267cb89eeb .gnulib
+  #  b653eda3ac4864de205419d9f41eec267cb89eeb .gnulib (v0.0-2286-gb653eda)
+  _submodule_hash = sed 's/.//;s/ .*//'
+  _update_required := $(shell						\
+      actual=$$(git submodule status | $(_submodule_hash));		\
+      stamp="$$($(_submodule_hash) $(_curr_status) 2>/dev/null)";	\
+      test "$$stamp" = "$$actual"; echo $$?)
   ifeq (1,$(_update_required))
     $(error gnulib update required; run ./autogen.sh first)
   endif