[PATCH cygport v3] autotools.cygclass: correctly detect Autoconf 2.70+

[Adam Dinwoodie <adam@dinwoodie.org>]

The latest version of Autoconf is 2.71, but the version detection
incorrectly considers 2.70 and higher as being the same as 2.59 and
lower for the purposes of specifying documentation directories.  Correct
that, and make the version detection a bit more future-proof by parsing
out the actual version parts and performing numeric comparison.

While we're at it, add a bit more commentary explaining the intent of
the different behaviour over the different Autoconf versions.
---
Interdiff against v2:
  diff --git a/cygclass/autotools.cygclass b/cygclass/autotools.cygclass
  index 38ac8f0..b40828b 100644
  --- a/cygclass/autotools.cygclass
  +++ b/cygclass/autotools.cygclass
  @@ -652,7 +652,7 @@ cygconf() {
   	fi
   
   	configure="${confdir}/configure"
  -	confver=$(grep -m 1 'GNU Autoconf' ${configure} | cut -d ' ' -f 6)
  +	confver="$("$configure" --version | sed -rn 's/.*GNU Autoconf ([0-9\.]+)/\1/p')"
   	confver_maj=${confver%%.*}
   	confver_min=${confver##*.}
   	if [ $confver_maj -ne 2 ]

 cygclass/autotools.cygclass | 40 ++++++++++++++++++++++++++-----------
 1 file changed, 28 insertions(+), 12 deletions(-)

diff --git a/cygclass/autotools.cygclass b/cygclass/autotools.cygclass
index cce9be0..b40828b 100644
--- a/cygclass/autotools.cygclass
+++ b/cygclass/autotools.cygclass
@@ -619,6 +619,8 @@ cygconf() {
 	local confdir;
 	local configure;
 	local confver;
+	local confver_maj;
+	local confver_min;
 	local f;
 	local foo_config;
 	local prefix;
@@ -650,7 +652,13 @@ cygconf() {
 	fi
 
 	configure="${confdir}/configure"
-	confver=$(grep -m 1 'GNU Autoconf' ${configure} | cut -d ' ' -f 6)
+	confver="$("$configure" --version | sed -rn 's/.*GNU Autoconf ([0-9\.]+)/\1/p')"
+	confver_maj=${confver%%.*}
+	confver_min=${confver##*.}
+	if [ $confver_maj -ne 2 ]
+	then
+		error "unexpected autoconf version";
+	fi
 
 	# AC_CONFIG_FILES should not be dist'ed, but it sometimes happens anyway
 	eval $(grep -h '^ac_config_files=' ${configure})
@@ -678,18 +686,26 @@ cygconf() {
 		confargs+=" --libdir=${prefix}/${MULTILIB_LIBDIR}"
 	fi
 
-	case "x${confver}" in
-		x2.6[0-9]*)
-			confargs+=" --docdir=/usr/share/doc/${PN} --htmldir=/usr/share/doc/${PN}/html"
-			;;
-		*)
-			confargs+=" --infodir=${prefix}/share/info --mandir=${prefix}/share/man"
-			;;
-	esac
+	if [ $confver_min -ge 60 ]
+	then
+		# Autoconf version supports --docdir and --htmldir, which will
+		# need to be specified manually.  It also supports --infodir
+		# and --mandir, but the defaults for those match the FHS.
+		confargs+=" --docdir=/usr/share/doc/${PN} --htmldir=/usr/share/doc/${PN}/html"
+	else
+		# Autoconf version does not support --docdir or --htmldir, so
+		# don't specify those.  Set --infodir and --mandir, as those
+		# have defaults that don't match the FHS.
+		confargs+=" --infodir=${prefix}/share/info --mandir=${prefix}/share/man"
+	fi
 
-	case "x${confver}" in
-		x2.[5-9]*)	confargs+=" -C" ;;
-	esac
+
+	if [ $confver_min -ge 50 ]
+	then
+		# Always use a cache file; prior to 2.50, this was the default,
+		# thereafter it needs to be requested explicitly.
+		confargs+=" -C"
+	fi
 
 	if cross_compiling || inherited toolchain
 	then
-- 
2.35.1