Split git-issue.sh into multiple files

[vyrondrosos]

With the main script file nearing 1200 lines of code --and my GSoC version at 1500-- and getting a bit unwieldy, I was considering splitting out some of the functions to a secondary source file(for example the ones concerning GitHub/GitLab import/export). Would that be OK, or would it be preferable to keep it to the single file, e.g for easier installation?

[dspinellis]

Good point! Some files would then need to be installed in a library folder (e.g. /usr/lib/git-issue. Is there precedent for this? Where are Git internal helper files located? How is then installation handled? Alternatively, the split could involve creating some internal helper binaries e.g. git-issue-import git-issue-export and install them as usual in a bin folder.

[vyrondrosos]

Those are some good points! It seems that git does install some library script files under /usr/lib/git-core, so I think that installing a /usr/lib/git-issue directory wouldn't be unprecedented. The 'separate executables for some subcommands' method is certainly interesting and could be useful but I believe there still would need to be a library file for them to source, since most commands currently rely on some common helper functions.