Introduce global gap variable GAP_jl

[lgoettgens]

Initial step towards #1053.

I would only call it resolved, once the special case for Julia.GAP is indeed removed.

[codecov]

Codecov Report

Attention: Patch coverage is 80.76923% with 5 lines in your changes missing coverage. Please review.

Project coverage is 82.74%. Comparing base (be6e4e2) to head (2fe0d26).
Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/JuliaInterface/gap/convert.gi	63.63%	4 Missing ⚠️
pkg/JuliaInterface/gap/JuliaInterface.gi	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1126      +/-   ##
==========================================
+ Coverage   74.66%   82.74%   +8.07%     
==========================================
  Files          55       50       -5     
  Lines        4713     3824     -889     
==========================================
- Hits         3519     3164     -355     
+ Misses       1194      660     -534     

Files with missing lines	Coverage Δ
gap/exec.g	100.00% <100.00%> (ø)
pkg/JuliaInterface/gap/JuliaInterface.gd	100.00% <ø> (ø)
pkg/JuliaInterface/gap/calls.gi	96.66% <100.00%> (ø)
pkg/JuliaInterface/gap/convert.gd	100.00% <ø> (ø)
pkg/JuliaInterface/gap/juliahelp.g	90.38% <100.00%> (ø)
pkg/JuliaInterface/read.g	88.00% <100.00%> (ø)
pkg/JuliaInterface/gap/JuliaInterface.gi	91.46% <80.00%> (ø)
pkg/JuliaInterface/gap/convert.gi	68.11% <63.63%> (ø)

... and 13 files with indirect coverage changes

[fingolfin]

Thinking this through: the immediate name for this object that comes to mind is just GAP, on the top level. But that somehow "feels" wrong, or at least pretentious for us to claim that name. It feels as if a global variable with this name should either not exist, or "belong" to the GAP library.

So GAP_jl then seems rather natural. I can't say I love it (no offense), but as my language makes clear, everything I am saying here is about "feeling" and so extremely subjective anyway.

Of course it somewhat breaks with the usual GAP naming conventions that suggest CamelCase for globals, but GAPJl or GAPJL don't seem seem better, and GAPJulia is worse.

I am pretty sure I'll get used to GAP_jl if we use it shrug.

If we do this, then we should also consider renaming the global Oscar object in OscarInterface to Oscar_jl (or rather: have both names, at least for a while, but move everything to use Oscar_jl).

All that said, I'd really like to hear from @ThomasBreuer, perhaps he sees something I am not or has some other ideas and suggestions.

[ThomasBreuer]

I would expect that the variable name GAP in a GAP session describes some important object of this GAP session, for example we could have called the GAPInfo record just GAP.
Inside a GAP session, using the name GAP for a Julia module would indeed be irritating.

Since we really need a variable for this module, I think GAP_jl is fine.

I found Julia.GAP very elegant: It expresses that it is something in the Julia world, and relative to that, GAP is exactly what one means.

I think there is no naming problem in the other direction: In Julia, GAP stands for the Julia module GAP, and GAP.Globals stands for the objects on the GAP side --the only problem is the ambiguity of GAP in sentences like this.

[ThomasBreuer]

see the comment which I just made

(I had thought that I had approved this pull request on Friday.)