man pages: Escape interpolated Make variables.

	* makevarescape.sed: Transform - to \-, ~ to \(ti, and so forth,
	(with an extra layer of backslashes--see below) so that Makefile
	variables containing ASCII characters that do not represent
	themselves literally in *roff (see groff_char(7)) are correctly
	interpolated into man page text.

	* Makefile.am (.man): Transform Makefile variables with the
	above script when interpolating them into man page text.

	Note that while the script, combined with this target, will
	transform ` to \(ga, including grave accents in Makefile
	variables is likely to fail when the shell lexes the argument to
	echo within the old-style command substitution ``.  Testing
	shows that grave accents should work[1] if POSIX-style command
	substitution $() is done instead.  However, $() is less
	portable.  (Triple-escaping grave accents \\\` inside the
	interpolated Makefile variable will work, but is not attempted
	at present.)

	Note also that the amount of backslash-escaping in the sed
	script is excessive (and incorrect) for normal purposes, but
	required here because a command substitution is being nested
	inside yet another invocation of sed.

	[1] For this target; no assurances about the good behavior of
	unusual characters in Makefile variables in other aspects of the
	groff build are offered.

	Fixes <https://savannah.gnu.org/bugs/index.php?55004>.

Signed-off-by: G. Branden Robinson <g.branden.robinson@gmail.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/makevarescape.sed b/makevarescape.sed
new file mode 100644
index 000000000..54f551300
--- /dev/null
+++ b/makevarescape.sed
@@ -0,0 +1,6 @@
+s/\\/\\\\e/g
+s/'/\\\\(aq/g
+s/-/\\\\&/g
+s/\^/\\\\(ha/g
+s/`/\\\\(ga/g
+s/~/\\\\(ti/g