make-dist: Add script to generate release tarballs

Because the source archives from GitHub tags may not always produce the
same tarball when fetching at different times. Having proper tarballs
for releases also allows signing them i.e. with PGP.

.gitattributes

@@ -0,0 +1,3 @@
+/.gitignore export-ignore
+/.travis.yml export-ignore
+/make-dist export-ignore

make-dist

@@ -0,0 +1,10 @@
+#! /bin/sh
+set -e
+
+GIT_TAG=$(git describe --tags HEAD)
+VERSION=${GIT_TAG#v}
+PV="ngx-fancyindex-${VERSION}"
+
+set -x
+git archive --worktree-attributes --prefix="${PV}/" -o "${PV}.tar" "${GIT_TAG}"
+xz -f9 "${PV}.tar"