Add contrib Dockerfile about how to build from tarball

- rename README.txt -> README.md
- Add contrib Dockerfile as sample how to build from tarball
- Fix bashism 'set -o posix'

1 files changed, 29 insertions, 0 deletions

diff --git a/contrib/build-using-docker/README.md b/contrib/build-using-docker/README.md
new file mode 100644
index 0000000..503136e
--- /dev/null
+++ b/contrib/build-using-docker/README.md
@@ -0,0 +1,29 @@
+
+Showcase how to build and install
+=================================
+
+Make and install inside a dockerimage.
+
+```sh
+    curl -sSL http://git.hiddenalpha.ch/bulk-ln.git/plain/contrib/build-using-docker/Dockerfile | sudo docker build . -f -
+```
+
+Afer that we can use the image hash printed in last line to refer to our built
+image (replace IMG_REF in commands below by that hash). Alternatively we could
+add [`--tag`](https://docs.docker.com/engine/reference/commandline/build/)
+option to our build command to give the resulting image a name.
+
+Most probably we wanna get the distribution archive. We can copy it out the
+dockerimage to our host using:
+
+```sh
+    sudo docker run --rm -i  IMG_REF  sh -c 'true && cd dist && tar c *' | tar x
+```
+
+Or if we wanna browse the image or play around with the built utility we could
+launch a shell. Once in the shell, try `bulk-ln --help`.
+
+```sh
+    sudo docker run --rm -ti  IMG_REF  sh
+```
+