gnulib: update

bootstrap

@@ -4,7 +4,7 @@ scriptversion=2021-04-11.09; # UTC
 
 # Bootstrap this package from checked-out sources.
 
-# Copyright (C) 2003-2021 Free Software Foundation, Inc.
+# Copyright (C) 2003-2022 Free Software Foundation, Inc.
 
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -763,9 +763,25 @@ if $use_gnulib; then
       shallow=
       if test -z "$GNULIB_REVISION"; then
         git clone -h 2>&1 | grep -- --depth > /dev/null && shallow='--depth 2'
+        git clone $shallow ${GNULIB_URL:-$default_gnulib_url} "$gnulib_path" \
+          || cleanup_gnulib
+      else
+        git fetch -h 2>&1 | grep -- --depth > /dev/null && shallow='--depth 2'
+        mkdir -p "$gnulib_path"
+        # Only want a shallow checkout of $GNULIB_REVISION, but git does not
+        # support cloning by commit hash. So attempt a shallow fetch by commit
+        # hash to minimize the amount of data downloaded and changes needed to
+        # be processed, which can drastically reduce download and processing
+        # time for checkout. If the fetch by commit fails, a shallow fetch can
+        # not be performed because we do not know what the depth of the commit
+        # is without fetching all commits. So fallback to fetching all commits.
+        git -C "$gnulib_path" init
+        git -C "$gnulib_path" remote add origin ${GNULIB_URL:-$default_gnulib_url}
+        git -C "$gnulib_path" fetch $shallow origin "$GNULIB_REVISION" \
+          || git -C "$gnulib_path" fetch origin \
+          || cleanup_gnulib
+        git -C "$gnulib_path" reset --hard FETCH_HEAD
       fi
-      git clone $shallow ${GNULIB_URL:-$default_gnulib_url} "$gnulib_path" \
-        || cleanup_gnulib
 
       trap - 1 2 13 15
     fi