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, 12 insertions, 12 deletions

diff --git a/doc/automake.texi b/doc/automake.texi
index dbe222d20..050c9811d 100644
--- a/doc/automake.texi
+++ b/doc/automake.texi
@@ -2277,7 +2277,7 @@ support new architectures and fix probes broken by changes in new
 kernel versions.  Each new release of Automake comes with up-to-date
 copies of these programs.  If your copy of Automake is getting old,
 you are encouraged to fetch the latest versions of these files from
-@url{http://savannah.gnu.org/git/?group=config} before making a
+@url{https://savannah.gnu.org/git/?group=config} before making a
 release.
 
 @item depcomp
@@ -2321,7 +2321,7 @@ testsuite harness.
 Not a program, this file is required for @samp{make dvi}, @samp{make
 ps} and @samp{make pdf} to work when Texinfo sources are in the
 package.  The latest version can be downloaded from
-@url{http://www.gnu.org/software/texinfo/}.
+@url{https://www.gnu.org/software/texinfo/}.
 
 @item ylwrap
 This program wraps @command{lex} and @command{yacc} to rename their
@@ -9857,7 +9857,7 @@ a Java-based project implementing both a TAP producer and a TAP consumer.
 @node DejaGnu Tests
 @section DejaGnu Tests
 
-If @uref{ftp://ftp.gnu.org/gnu/dejagnu/, @command{dejagnu}} appears in
+If @uref{https://ftp.gnu.org/gnu/dejagnu/, @command{dejagnu}} appears in
 @code{AUTOMAKE_OPTIONS}, then a @command{dejagnu}-based test suite is
 assumed.  The variable @code{DEJATOOL} is a list of names that are
 passed, one at a time, as the @option{--tool} argument to
@@ -10461,7 +10461,7 @@ performing @ref{Automatic Rule Rewriting, , VPATH rewrites, autoconf,
 The Autoconf Manual}).
 
 Finally, Automake also emits rules to support the
-@uref{http://www.gnu.org/software/global/, GNU Global Tags program}.
+@uref{https://www.gnu.org/software/global/, GNU Global Tags program}.
 The @code{GTAGS} rule runs Global Tags and puts the
 result in the top build directory.  The variable @code{GTAGS_ARGS}
 holds arguments that are passed to @command{gtags}.
@@ -11050,7 +11050,7 @@ If the @option{--add-missing} option is given, @command{automake} will
 add a generic version of the @file{INSTALL} file as well as the
 @file{COPYING} file containing the text of the current version of the
 GNU General Public License existing at the time of this Automake release
-(version 3 as this is written, @uref{http://www.gnu.org/@/copyleft/@/gpl.html}).
+(version 3 as this is written, @uref{https://www.gnu.org/@/copyleft/@/gpl.html}).
 However, an existing @file{COPYING} file will never be overwritten by
 @command{automake}.
 
@@ -13077,8 +13077,8 @@ To make it possible for us to fix a bug, please report it. In order to
 do so effectively, it helps to know when and how to do it.
 
 Before reporting a bug, it is a good idea to see if it is already known.
-You can look at the @uref{http://debbugs.gnu.org/, GNU Bug Tracker}
-and the @uref{http://lists.gnu.org/@/archive/@/html/@/bug-automake/,
+You can look at the @uref{https://debbugs.gnu.org/, GNU Bug Tracker}
+and the @uref{https://lists.gnu.org/@/archive/@/html/@/bug-automake/,
 bug-automake mailing list archives} for previous bug reports.  We
 previously used a
 @uref{http://sourceware.org/@/cgi-bin/@/gnatsweb.pl?database=automake,
@@ -13097,7 +13097,7 @@ features.
 
 For a bug report, a feature request or other suggestions, please send
 email to @email{@value{PACKAGE_BUGREPORT}}.  This will then open a new
-bug in the @uref{http://debbugs.gnu.org/@/automake, bug tracker}.  Be
+bug in the @uref{https://debbugs.gnu.org/@/automake, bug tracker}.  Be
 sure to include the versions of Autoconf and Automake that you use.
 Ideally, post a minimal @file{Makefile.am} and @file{configure.ac} that
 reproduces the problem you encounter.  If you have encountered test
diff --git a/doc/help2man b/doc/help2man
index 829a8713b..f7a9c455c 100755
--- a/doc/help2man
+++ b/doc/help2man
@@ -15,10 +15,10 @@
 # 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 Brendan O'Dea <bod@debian.org>
-# Available from ftp://ftp.gnu.org/gnu/help2man/
+# Available from https://ftp.gnu.org/gnu/help2man/
 
 use 5.008;
 use strict;
@@ -759,7 +759,7 @@ sub convert_option
 }
 
 # Insert spacing escape characters \, and \/ before and after italic text.  See
-# http://www.gnu.org/software/groff/manual/html_node/Ligatures-and-Kerning.html
+# https://www.gnu.org/software/groff/manual/html_node/Ligatures-and-Kerning.html
 sub fix_italic_spacing
 {
     local $_ = shift;
diff --git a/doc/local.mk b/doc/local.mk
index 807c29308..b6742e6aa 100644
--- a/doc/local.mk
+++ b/doc/local.mk
@@ -13,7 +13,7 @@
 ## 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/>.
 
 ## ---------------- ##
 ##  Documentation.  ##