Split autogen.sh into autopull.sh and autogen.sh.

* autopull.sh: New file, based on autogen.sh.
* autogen.sh: Remove code that was moved to autopull.sh.
* Makefile.in (SOURCE_FILES): Add autogen.sh.

autopull.sh

@@ -0,0 +1,42 @@
+#!/bin/sh
+# Convenience script for fetching auxiliary files that are omitted from
+# the version control repository of this package.
+#
+# This script requires either
+#   - the GNULIB_TOOL environment variable pointing to the gnulib-tool script
+#     in a gnulib checkout, or
+#   - an internet connection.
+
+# 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
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+# Usage: ./autopull.sh
+
+GNULIB_REPO_URL="https://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=blob_plain;hb=HEAD;f="
+
+for file in build-aux/install-sh build-aux/mkinstalldirs \
+            build-aux/compile build-aux/ar-lib \
+            lib/filename.h; do
+  if test -n "$GNULIB_TOOL"; then
+    $GNULIB_TOOL --copy-file $file $file
+  else
+    wget -q --timeout=5 -O $file.tmp "${GNULIB_REPO_URL}$file" \
+      && mv $file.tmp $file
+  fi
+done
+chmod a+x build-aux/install-sh build-aux/mkinstalldirs \
+          build-aux/compile build-aux/ar-lib
+
+echo "$0: done.  Now you can run './autogen.sh'."