Maktaba added to runtimepath twice when symlinked and installed manually

[glts]

Minor issue. When using the manual installation procedure described at https://github.com/google/maktaba/blob/master/vroom/manual.vroom, and Maktaba is symlinked, then it is added to the runtimepath twice, once with the symlink location and once with the resolved symlink. See also #31.

Example vimrc:

" ~/.vim -> ~/code/dotfiles/.vim
set runtimepath+=~/.vim/maktaba

Resulting runtimepath is ...,/home/glts/code/dotfiles/.vim/maktaba,.../home/glts/.vim/maktaba.

[dbarnett]

It looks like the problem is that maktaba#plugin#GetOrInstall doesn't call maktaba#plugin#Detect first. It tries to install maktaba instead of finding it on rtp, creating a plugin dict for it, and then finding that plugin dict and skipping installation.

I'd have to check if maktaba#rtp#Split caching is enough to keep this from causing a significant performance regression. Otherwise, we might still be able to optimize it so it's not a problem.

[fowles]

https://github.com/google/vim-codefmt/issues/6 is related