Add bash completions

[TobiPeterG]

This will complete started commands and provide a list of possible commands and options.

Closes #61

Unfortunately, we can't access the available snapshots, so the user still has to know which ones are available on his system. Equally, we can't enter snapshots to find kernel versions, so we recommend only the currently installed kernels.

[lnussel]

I'd probably add a hidden function to sdbootutil that can be eval'd from the completion script to avoid duplicating all that code

[TobiPeterG]

I'd probably add a hidden function to sdbootutil that can be eval'd from the completion script to avoid duplicating all that code

I've looked a bit into how bash completion works and it seems like the bash completion has to happen in the same shell context. So I can A) source the sdbootutil script, but that would execute the functions that might fail as the bash completion can be called as non-super user
B) call a function in sdbootutil where I echo the recommendations, but that would also not be a nice solution
C) Create two functions in sdbootutil that are callable that return the architecture/image name and kernels in the current snapshot.

Or do you have a different idea?
I agree that the code duplication isn't nice

[lnussel]

something like eval $(sdbootutil _print_bash_completion_data)

[TobiPeterG]

something like eval $(sdbootutil _print_bash_completion_data)

I've tried to implement this. I couldn't test it yet though, but please tell me if this is what you had in mind :)
The code also isn't nice yet, it's just thought as a concept currently :)

[lnussel]

almost there

[TobiPeterG]

@aplanas can you have a look at this one please? :)

[aplanas]

@TobiPeterG the PR is looking good. Give me some time to test it a bit

[TobiPeterG]

Should I just rebase or do you have any issues with the functionality/code that I should fix with a rebase?

[aplanas]

Yes please, do a rebase. But I need to research a bit more. I found a good reference

[aplanas]

I think we can split this PR is two: one for all the bash completions, but another one for the commands refactoring. This last part is the main source of conflicts right now

[TobiPeterG]

Now depends on #172

I have refactored this PR and split it into multiple commits. Please have a look :)

[TobiPeterG]

To also support snapshots as completion, it would be the easiest to add a new option "--snapshot" that I can check for i nthe completion script. Otherwise it's impossible to know if the user wants to add an option or a snapshot number and I don't want to show both in one list.

[TobiPeterG]

Rebased :)

I added the "_none" function when no completion is useful.

[TobiPeterG]

@aplanas Rebased :)

[aplanas]

I would merge it after the commented issue

[aplanas]

Sorry that this takes so long : (

And thanks!

Many changes after this request of change

[TobiPeterG]

Sorry that this takes so long : (

And thanks!

All good :)