Use transient instead of magit-popup in magithub-feature-list

[mgcyung]

Fix #402

[vermiculus]

Hm, we should probably fix all the transient-related stuff in one go -- otherwise we'll fix one error and then find another. Would you have time to migrate each popup introduced here? (Search for magit-define-popup.)

If not (which is totally fine! I'm grateful for any help you can give me here), if you explicitly (require 'magit-popup) in each of the files that call magit-define-popup and add it explicitly to the Package-Requires header in magithub.el, does the project compile successfully? (Run make install test.)

[mgcyung]

How to deal with magit--set-popup-variable and magit--format-popup-variable:choices. There is an error in make install test

In toplevel form:
magithub-settings.el:383:1:Error: the following functions are not known to be defined: magit--set-popup-variable, magit--format-popup-variable:choices
emake: compiling magithub-settings.el...done
emake: Running target "compile" with function `emake-compile' with arguments ("~error-on-warn")...done
There were compile-time errors
make: *** [emake.mk:74: compile] Error 255

[mgcyung]

There is an error of no "magit-checkout-pull-request" when run "make install test". The following code snippet which is irrelevant to transient is also commented

;; (make-obsolete 'magithub-pull-request-checkout 'magit-checkout-pull-request "0.1.6")
;; (defalias 'magithub-pull-request-checkout #'magit-checkout-pull-request)

[vermiculus]

Great! I'll give this a quick run through tonight and give some feedback / merge as appropriate.

Thanks for taking this on!

[hexmode]

Please merge this PR. It works for me!

[vermiculus]

@hexmode I'm trusting you, here 😄

I've not had the bandwidth or frankly the energy for F/OSS work lately – I've been dealing with some safety-critical systems at work and they've been consuming all my efforts.

I'm merging this PR now. If it stops working, please let me know and I'll rewind ASAP.

[hexmode]

Thank you! testing now.