--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2010-11-20  Joel E. Denny  <joeldenny@joeldenny.org>
+
+	bootstrap: add bootstrap_sync option.
+	See discussion at
+	<http://lists.gnu.org/archive/html/bug-gnulib/2010-10/msg00369.html>,
+	<http://lists.gnu.org/archive/html/bug-gnulib/2010-11/msg00200.html>.
+	* build-aux/bootstrap: Accept --bootstrap-sync to update
+	bootstrap if it is not identical to the local gnulib's
+	bootstrap.  Accept bootstrap_sync=true in bootstrap.conf to
+	enable this by default.  Accept --no-bootstrap-sync to disable
+	it.
+
 2010-11-20  Bruno Haible  <bruno@clisp.org>
 
 	Ensure that <features.h> is included before __GLIBC__ is tested.

--- a/build-aux/bootstrap
+++ b/build-aux/bootstrap
@@ -1,6 +1,6 @@
 #! /bin/sh
 # Print a version string.
-scriptversion=2010-11-12.21; # UTC
+scriptversion=2010-11-20.03; # UTC
 
 # Bootstrap this package from checked-out sources.
 
@@ -54,6 +54,12 @@
                           have gnulib sources on your machine, and
                           do not want to waste your bandwidth downloading
                           them again.  Defaults to \$GNULIB_SRCDIR.
+ --bootstrap-sync         If this bootstrap script is not identical to
+                          the version in the local gnulib sources,
+                          update this script, and then restart it with
+                          /bin/sh or the shell \$CONFIG_SHELL if
+                          defined.
+ --no-bootstrap-sync      Do not check whether bootstrap is out of sync.
  --copy                   Copy files instead of creating symbolic links.
  --force                  Attempt to bootstrap even if the sources seem
                           not to have been checked out.
@@ -168,6 +174,10 @@
 # on which version control system (if any) is used in the source directory.
 vc_ignore=auto
 
+# Set this to true in bootstrap.conf to enable --bootstrap-sync by
+# default.
+bootstrap_sync=false
+
 # find_tool ENVVAR NAMES...
 # -------------------------
 # Search for a required program.  Use the value of ENVVAR, if set,
@@ -239,6 +249,10 @@
     checkout_only_file=;;
   --copy)
     copy=true;;
+  --bootstrap-sync)
+    bootstrap_sync=true;;
+  --no-bootstrap-sync)
+    bootstrap_sync=false;;
   *)
     echo >&2 "$0: $option: unknown option"
     exit 1;;
@@ -501,6 +515,16 @@
   ;;
 esac
 
+if $bootstrap_sync; then
+  cmp -s "$0" "$GNULIB_SRCDIR/build-aux/bootstrap" || {
+    echo "$0: updating bootstrap and restarting..."
+    exec sh -c \
+      'cp "$1" "$2" && shift && exec "${CONFIG_SHELL-/bin/sh}" "$@"' \
+      -- "$GNULIB_SRCDIR/build-aux/bootstrap" \
+      "$0" "$@" --no-bootstrap-sync
+  }
+fi
+
 gnulib_tool=$GNULIB_SRCDIR/gnulib-tool
 <$gnulib_tool || exit