DC2: DIALS installer

Proposal	DIALS installer
Created	2020-02-23
Status	Accepted

1. WP1: We can use conda-pack to pack up the environment.
   • This does not depend on anything else really, so we can start here.
   • Having this would mean that we have a valid (non-relocated) conda environment in the installation, which would resolve eg. the readline/ncurses issues. So this has an immediate benefit.
   • The installer should be able to run offline.
   • Workflow would be:
     • use conda-pack to pack up the correct environment
     • unpack that manually
     • do the equivalent of the create-installer script using the conda-pack‘d environment
   • And then on installation:
     • unpack the conda-pack‘d environment
     • run the conda-pack post install fixer-upper
     • do the remainder of the DIALS installer bit
     • done
   • Also: disconnect the DIALS installer scripts from libtbx
2. WP2: Support an offline developer installation. Currently this is covered by downloading a release.
   • Add a --download option to bootstrap that
     • downloads and unpacks miniconda
     • tells miniconda to resolve and download the environment (not: install)
     • clones all sources repositories
   • Add an --offline option to bootstrap that
     • takes all the above files and does the base & build step
3. WP3: have a run-time spec and a development environment
   • Split up eg. linux.txt into run/dev, and then there will be some overlap between platforms and it can probably be simplified
   • Not on the critical path.
   • This would allow us to remove C compilers, alabaster, sphinx, scons, pytest, …, and make
4. WP4: The installer should only install user installation, not development installation
   • Not reasonable to provide an ‘upgrade’ path, as that would need to rebuild everything anyway. We can provide manual instructions for converting.
   • With this we can remove all C++ source code and intermediate files

Ancillary:

• Make bootstrap print out ‘you’re in uncharted territory’ if you change the Python version on a release build that has otherwise pinned conda-forge packages. Unpin the CF packages.