Tab completion does not work with C-Shell

[jessemapel]

ISIS version(s) affected: 3.6.2

Description
Using 3.6.2 and the conda environment installation, tab completion does not work for application parameters and files.

How to reproduce

1. Follow the conda installation instructions for 3.6.2
2. Activate the conda environment with 3.6.2 installed
3. enter cam2map and then tab
   1. this should list all of cam2map's paramters
4. enter cam2map from= and then tab
   1. this should list all of the cube files in the current directory

Additional context
more info from @lwellerastro and possible solution from @scsides here

Related to #1599

[SgStapleton]

Possible Solution: Move tab complete logic from /etc/conda/activate.d/env_vars.csh to it's own script inside the isis3 repo scripts and call it from the env_vars.csh. (Repeat same for bash, but logic needs to be re-written for bash.)

[SgStapleton]

As most users are moved/moving to bash, does it make sense to complete this for bash as well and rename this ticket?

[jessemapel]

@SgStapleton If they get worked on at the same time, I think that's good

[scsides]

Getting tcsh tab completion going is trivial (a few minutes), Jesse has already done this by hand using my script, so we know what it will take. Getting it working for bash will be significantly more work (hours). The syntax for bash is completely different than the existing tcsh syntax, and will have to be learned before work can begin. There is some overlap though, the simple changes for tcsh will also need to be done for bash.

[jessemapel]

@scsides I've manually added your script, but we need to make it automatic or a part of the isis3VarInit script.

[scsides]

Thanks, I clarified it

[SgStapleton]

Sorry I have not been updating on this ticket. I have one simple question for the tcsh process: It looks like the isis3VarInit.py script is writing the bash files for activate and deactivate, but I can't seem to figure out where the .tcsh files are being written? All the other logic should be in place for tcsh to call a script in $CONDA_PREFIX/scripts. It WAS very simple.

The bash is another story entirely. I have been looking into the complete and compgen commands in bash and it is going to need to be handled ENTIRELY different. I have been playing around with it getting some ideas of what can be done, but this is going to be a much bigger time sink.

[SgStapleton]

Once this PR is merged, I will be closing this ticket as there already exists a ticket for bash tab completion: #1599