implements curl docker image and build/test/push processes

[xquery]

This is a refactor of the last effort (#4) where we simplify to implement a single image (alpine based) and resolves #5 (and supersedes the original curl/curl#3714):

• fixed -enable-static to —enable-static
• added and will push with specific tag
• removed cruft (.la, .a files)
• remove curl from alpine in a sane manner
• ensure ca certs is avail (resolves which ssl backend and how to keep ca updated #3)
• add security scan
• pinned alpine version (3.10.2)
• and a lot of other minor little tweaks
• run under non root user

Once this gets reviewed we will push to docker hub to show up here

https://cloud.docker.com/u/curlimages/repository/docker/curlimages/curl/general

[xquery]

turns out my .gitignore was ignoring 'Makefile' ! fixed it

[cmeister2]

Random thoughts:

If I were doing this for work, I would:

• Have Dockerfile taking a curl-version argument
• Builder step of Dockerfile:
  • Download, compile and install curl
• End image step:
  • Copy compiled curl and libraries into place (and install any dependencies).

I think downloading the source outside of the Dockerfile clutters up the working directory for no real benefit.

I think pinning the dependencies to a single curl-version variable is much cleaner than autodetecting the latest version. It allows you more control over what you're releasing.

Please let's not have recursive Makefiles if we don't absolutely need them.

---

Up to you how many of these you want to do. Some of these might be nit-picking but I feel like if we can make this as maintainable as possible up front, let's try.