Makefile `fullinstall` target not working on default Ubuntu 20.04

We have been working on the migration of SVN repositories and came across reposurgeon. Thank you for this wonderful tool!

  1. The following line does not work on Ubuntu 20.04: (https://gitlab.com/esr/reposurgeon/-/blob/master/Makefile#L71)
sudo apt-get install asciidoctor awk

As the original awk package is now renamed to be original-awk.

Running make helpers will result in the following error:

Package awk is a virtual package provided by:
  original-awk 2012-12-20-6
  mawk 1.3.4.20200120-2
  gawk 1:5.0.1+dfsg-1
You should explicitly select one to install.

E: Package 'awk' has no installation candidate

Any of these packages already install awk, I suspect an easier alternative is to either require the user to have awk installed or detect whether awk is available in the system before proceeding to install (https://gitlab.com/esr/reposurgeon/-/blob/master/Makefile#L33 already requires awk to be present).

  1. make testhelpers does not work due to (https://gitlab.com/esr/reposurgeon/-/blob/master/Makefile#L74) the requested package hg-git-fast-import does not exist on Ubuntu.

For normal users, this package is only available as a Rust Crate or via Snap. The suggestion is to remove this package from the Makefile and document whether hg-git-fast-import is a mandatory install of reposurgeon, and if so, link to https://github.com/kilork/hg-git-fast-import for detailed installation instructions.