Prefer https: URLs

In Gnulib, Emacs, etc. we are changing ftp: and http: URLs to use
https:, to discourage man-in-the-middle attacks when downloading
software. The attached patch propagates these changes upstream to
Automake.  This patch does not affect files that Automake is
downstream of, which I'll patch separately.

Althouth the resources are not secret, plain HTTP is vulnerable to
malicious routers that tamper with responses from GNU servers,
and this sort of thing is all too common when people in some other
countries browse US-based websites. See, for example:

Aceto G, Botta A, Pescapé A, Awan MF, Ahmad T, Qaisar
S. Analyzing internet censorship in Pakistan. RTSI
2016. https://dx.doi.org/10.1109/RTSI.2016.7740626

HTTPS is not a complete solution here, but it can be a significant
help. The GNU project regularly serves up code to users, so we should
take some care here.

3 files changed, 8 insertions, 8 deletions

diff --git a/bin/aclocal.in b/bin/aclocal.in
index 87dc9d6ec..016550a49 100644
--- a/bin/aclocal.in
+++ b/bin/aclocal.in
@@ -20,7 +20,7 @@ eval 'case $# in 0) exec @PERL@ -S "$0";; *) exec @PERL@ -S "$0" "$@";; esac'
 # 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 <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 # Written by Tom Tromey <tromey@redhat.com>, and
 # Alexandre Duret-Lutz <adl@gnu.org>.
@@ -664,7 +664,7 @@ sub scan_file ($$$)
 	    {
 	      msg ('syntax', "$file:$.", "underquoted definition of $2"
 		   . "\n  run info Automake 'Extending aclocal'\n"
-		   . "  or see http://www.gnu.org/software/automake/manual/"
+		   . "  or see https://www.gnu.org/software/automake/manual/"
 		   . "automake.html#Extending-aclocal")
 		unless $underquoted_manual_once;
 	      $underquoted_manual_once = 1;
@@ -768,7 +768,7 @@ sub trace_used_macros ()
   # When AC_CONFIG_MACRO_DIRS is used, avoid possible spurious warnings
   # from autom4te about macros being "m4_require'd but not m4_defun'd";
   # for more background, see:
-  # http://lists.gnu.org/archive/html/autoconf-patches/2012-11/msg00004.html
+  # https://lists.gnu.org/archive/html/autoconf-patches/2012-11/msg00004.html
   # as well as autoconf commit 'v2.69-44-g1ed0548', "warn: allow aclocal
   # to silence m4_require warnings".
   my $early_m4_code .= "m4_define([m4_require_silent_probe], [-])";
@@ -1062,7 +1062,7 @@ Warning categories include:
 
 Report bugs to <@PACKAGE_BUGREPORT@>.
 GNU Automake home page: <@PACKAGE_URL@>.
-General help using GNU software: <http://www.gnu.org/gethelp/>.
+General help using GNU software: <https://www.gnu.org/gethelp/>.
 EOF
   exit $status;
 }
diff --git a/bin/automake.in b/bin/automake.in
index 62eb13fe5..895f0b5c9 100644
--- a/bin/automake.in
+++ b/bin/automake.in
@@ -19,7 +19,7 @@ eval 'case $# in 0) exec @PERL@ -S "$0";; *) exec @PERL@ -S "$0" "$@";; esac'
 # 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 <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 # Originally written by David Mackenzie <djm@gnu.ai.mit.edu>.
 # Perl reimplementation by Tom Tromey <tromey@redhat.com>, and
@@ -5238,7 +5238,7 @@ sub scan_autoconf_traces
 	    {
               msg 'obsolete', $where, <<'EOF';
 AM_INIT_AUTOMAKE: two- and three-arguments forms are deprecated.  For more info, see:
-http://www.gnu.org/software/automake/manual/automake.html#Modernize-AM_005fINIT_005fAUTOMAKE-invocation
+https://www.gnu.org/software/automake/manual/automake.html#Modernize-AM_005fINIT_005fAUTOMAKE-invocation
 EOF
 	      $package_version = $args[2];
 	      $package_version_location = $where;
@@ -7928,7 +7928,7 @@ Library files:
     print '
 Report bugs to <@PACKAGE_BUGREPORT@>.
 GNU Automake home page: <@PACKAGE_URL@>.
-General help using GNU software: <http://www.gnu.org/gethelp/>.
+General help using GNU software: <https://www.gnu.org/gethelp/>.
 ';
 
     # --help always returns 0 per GNU standards.
diff --git a/bin/local.mk b/bin/local.mk
index c63f670b8..b5617f50a 100644
--- a/bin/local.mk
+++ b/bin/local.mk
@@ -11,7 +11,7 @@
 ## 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 <http://www.gnu.org/licenses/>.
+## along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 ## ----------------------------------- ##
 ##  The automake and aclocal scripts.  ##