diff --git a/bootstrap b/bootstrap
index eddacfb6..002edf68 100755
--- a/bootstrap
+++ b/bootstrap
@@ -1,6 +1,6 @@
 #! /bin/sh
 # Print a version string.
-scriptversion=2018-04-28.14; # UTC
+scriptversion=2018-05-27.20; # UTC
 
 # Bootstrap this package from checked-out sources.
 
@@ -47,6 +47,8 @@ PERL="${PERL-perl}"
 
 me=$0
 
+default_gnulib_url=git://git.sv.gnu.org/gnulib
+
 usage() {
   cat <<EOF
 Usage: $me [OPTION]...
@@ -76,6 +78,37 @@ contents are read as shell variables to configure the bootstrap.
 For build prerequisites, environment variables like \$AUTOCONF and \$AMTAR
 are honored.
 
+Gnulib sources can be fetched in various ways:
+
+ * If this package is in a git repository with a 'gnulib' submodule
+   configured, then that submodule is initialized and updated and sources
+   are fetched from there.  If \$GNULIB_SRCDIR is set (directly or via
+   --gnulib-srcdir) and is a git repository, then it is used as a reference.
+
+ * Otherwise, if \$GNULIB_SRCDIR is set (directly or via --gnulib-srcdir),
+   then sources are fetched from that local directory.  If it is a git
+   repository and \$GNULIB_REVISION is set, then that revision is checked
+   out.
+
+ * Otherwise, if this package is in a git repository with a 'gnulib'
+   submodule configured, then that submodule is initialized and updated and
+   sources are fetched from there.
+
+ * Otherwise, if the 'gnulib' directory does not exist, Gnulib sources are
+   cloned into that directory using git from \$GNULIB_URL, defaulting to
+   $default_gnulib_url.
+   If \$GNULIB_REVISION is set, then that revision is checked out.
+
+ * Otherwise, the existing Gnulib sources in the 'gnulib' directory are
+   used.  If it is a git repository and \$GNULIB_REVISION is set, then that
+   revision is checked out.
+
+If you maintain a package and want to pin a particular revision of the
+Gnulib sources that has been tested with your package, then there are two
+possible approaches: either configure a 'gnulib' submodule with the
+appropriate revision, or set \$GNULIB_REVISION (and if necessary
+\$GNULIB_URL) in $me.conf.
+
 Running without arguments will suffice in most cases.
 EOF
 }
@@ -634,9 +667,11 @@ if $use_gnulib; then
       trap cleanup_gnulib 1 2 13 15
 
       shallow=
-      git clone -h 2>&1 | grep -- --depth > /dev/null && shallow='--depth 2'
-      git clone $shallow git://git.sv.gnu.org/gnulib "$gnulib_path" ||
-        cleanup_gnulib
+      if test -z "$GNULIB_REVISION"; then
+        git clone -h 2>&1 | grep -- --depth > /dev/null && shallow='--depth 2'
+      fi
+      git clone $shallow ${GNULIB_URL:-$default_gnulib_url} "$gnulib_path" \
+        || cleanup_gnulib
 
       trap - 1 2 13 15
     fi
@@ -671,6 +706,11 @@ if $use_gnulib; then
     ;;
   esac
 
+  if test -d "$GNULIB_SRCDIR"/.git && test -n "$GNULIB_REVISION" \
+     && ! git_modules_config submodule.gnulib.url >/dev/null; then
+    (cd "$GNULIB_SRCDIR" && git checkout "$GNULIB_REVISION") || cleanup_gnulib
+  fi
+
   # $GNULIB_SRCDIR now points to the version of gnulib to use, and
   # we no longer need to use git or $gnulib_path below here.
 
diff --git a/gnulib b/gnulib
index 0d10473b..0d45ec7c 160000
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 0d10473be6fb40c42c0d10c3417a818b0ebfcce1
+Subproject commit 0d45ec7c033c165ad73a6509c7fa84aa67edf4ea
diff --git a/lib/.gitignore b/lib/.gitignore
index c833c2bb..39d86665 100644
--- a/lib/.gitignore
+++ b/lib/.gitignore
@@ -36,7 +36,6 @@
 /closeout.h
 /concat-filename.c
 /concat-filename.h
-/config.charset
 /config.h
 /config.in.h
 /configmake.h
@@ -159,9 +158,7 @@
 /rawmemchr.valgrind
 /realloc.c
 /ref-add.sed
-/ref-add.sin
 /ref-del.sed
-/ref-del.sin
 /sched.h
 /sched.in.h
 /sig-handler.c