-d: exclude non-directories

Adding flag, and supporting functionality for exluding entries that are
non-directories

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

test/cli/0006.sh

@@ -0,0 +1,33 @@
+#!/bin/bash
+set -e
+
+name=$(basename $0)
+root=$1
+gomtree=$(readlink -f ${root}/gomtree)
+t=$(mktemp -d /tmp/go-mtree.XXXXXX)
+
+echo "[${name}] Running in ${t}"
+# This test is for basic running check of manifest, and check against tar and file system
+#
+
+pushd ${root}
+
+git archive --format=tar HEAD^{tree} . > ${t}/${name}.tar
+
+prev_umask=$(umask)
+umask 0 # this is so the tar command can set the mode's properly
+mkdir -p ${t}/extract
+tar -C ${t}/extract/ -xf ${t}/${name}.tar
+umask ${prev_umask}
+
+# create manifest from tar, ignoring non directories
+${gomtree} -d -c -k type -T ${t}/${name}.tar > ${t}/${name}.mtree
+
+# check tar-manifest against the tar
+${gomtree} -d -f ${t}/${name}.mtree -T ${t}/${name}.tar
+
+# check filesystem-manifest against the filesystem
+${gomtree} -f ${t}/${name}.mtree -p ${t}/extract/
+
+popd
+rm -rf ${t}