From 62ff854174fa73fc5a26796b8857cd3c390c3959 Mon Sep 17 00:00:00 2001
From: Dimitrios Apostolou <address@hidden>
Date: Mon, 16 Mar 2015 13:09:06 +0100
Subject: [PATCH 1/1] GNU Tar now uses --hard-dereference when possible

Historically "make dist" tries to store only files inside the tarball,
avoiding all symlinks/hardlinks in order to bypass limitations of the
tar format (for example the "ustar" format allows only 100 characters
filenames for symlinks). For that reason -o (i.e. --dereference) has
been passed to the tar command.

However GNU Tar changed its behaviour since v1.24 and stores symlinks as
hardlinks if --dereference is passed. Thus we now need to pass
--hard-dereference to make sure no links are stored in the
tarball. Unfortunately this option is available since GNU tar v1.28,
which means that for versions 1.24-1.28 "make dist" will create tarballs
containing hardlinks, with all the limitations of the respective format
(see [1]).

[1] http://www.gnu.org/software/tar/manual/html_section/tar_68.html
---
 m4/tar.m4 | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/m4/tar.m4 b/m4/tar.m4
index d8054cb..c7fc521 100644
--- a/m4/tar.m4
+++ b/m4/tar.m4
@@ -72,18 +72,27 @@ m4_if([$1], [v7],
   _am_tools=${am_cv_prog_tar_$1-$_am_tools}
 
   for _am_tool in $_am_tools; do
     case $_am_tool in
     gnutar)
       for _am_tar in tar gnutar gtar; do
         AM_RUN_LOG([$_am_tar --version]) && break
       done
-      am__tar="$_am_tar --format=m4_if([$1], [pax], [posix], [$1]) -chf - "'"$$tardir"'
-      am__tar_="$_am_tar --format=m4_if([$1], [pax], [posix], [$1]) -chf - "'"$tardir"'
+      AM_RUN_LOG([$_am_tar --hard-dereference  2>&1 | grep 'unrecognized option'])
+      # Check if --hard-dereference is supported by this version of GNU Tar
+      if test "$ac_status" -eq 0; then
+        _am_gnutar_hard_dereference=false
+        am__tar="$_am_tar --format=m4_if([$1], [pax], [posix], [$1]) -chf - "'"$$tardir"'
+        am__tar_="$_am_tar --format=m4_if([$1], [pax], [posix], [$1]) -chf - "'"$tardir"'
+      else
+        _am_gnutar_hard_dereference=true
+        am__tar="$_am_tar --format=m4_if([$1], [pax], [posix], [$1]) --hard-dereference -chf - "'"$$tardir"'
+        am__tar_="$_am_tar --format=m4_if([$1], [pax], [posix], [$1]) --hard-dereference -chf - "'"$tardir"'
+      fi
       am__untar="$_am_tar -xf -"
       ;;
     plaintar)
       # Must skip GNU tar: if it does not support --format= it doesn't create
       # ustar tarball either.
       (tar --version) >/dev/null 2>&1 && continue
       am__tar='tar chf - "$$tardir"'
       am__tar_='tar chf - "$tardir"'
@@ -122,11 +131,21 @@ m4_if([$1], [v7],
       grep GrepMe conftest.dir/file >/dev/null 2>&1 && break
     fi
   done
   rm -rf conftest.dir
 
   AC_CACHE_VAL([am_cv_prog_tar_$1], [am_cv_prog_tar_$1=$_am_tool])
   AC_MSG_RESULT([$am_cv_prog_tar_$1])])
 
+  if test $_am_tool = gnutar; then
+    # We've checked already, so we're just printing here
+    AC_MSG_CHECKING([if GNU tar supports --hard-dereference])
+    if test x$_am_gnutar_hard_dereference = xtrue; then
+      AC_MSG_RESULT([yes])
+    else
+      AC_MSG_RESULT([no])
+    fi
+  fi
+
 AC_SUBST([am__tar])
 AC_SUBST([am__untar])
 ]) # _AM_PROG_TAR
-- 
1.9.1