Add rhubarb.vim for fugitive Github support
Add rhubarb.vim for fugitive Github support

We do most of our client work on Github,
and a large portion of our personal projects
are hosted there.

fugitive.vim currently supports
opening the current file in the current branch
in a browser at Github through the `Gbrowse` command.
That command is [slated to be removed to make fugitive
agnostic about coding sites](fugitive-docs).

The capability to quickly generate or view a Github URL
specific to the current branch
can be useful in PR reviews
or other discussions about code.

This change adds rhubarb.vim,
a plugin that implements the slated-to-be-removed
functionality of fugitive that works with Github.
It also provides the user with omni-completion (`<C-x><C-o>`)
to autocomplete Github issues, issue URLs, and collaborators.

[fugitive-docs]: https://github.com/tpope/vim-fugitive/blob/18d6d1ab82d9ac15586d7d3c1a36f9ef6fb50eae/doc/fugitive.txt

voanhduy1512/dotfiles,lannn/dotfiles,ajkamel/dotfiles,ncuesta/dotfiles,rootulp/dotfiles,moofish32/dotfiles,robkilby/dotfiles,soon0009/thoughtbot-dotfiles,toobulkeh/dotfiles,dainmiller/thoughtbot-dotfile-mods,soon0009/thoughtbot-dotfiles,T1D/dotfiles,aliceyoung9/dotfiles,Jiwoong/dotfiles,koerbcm/dotfiles,tsigo/dotfiles-thoughtbot,astoellis/dotfiles,ZloeSabo/dotfiles,kkelleey/dotfiles,Jiwoong/dotfiles,rootulp/dotfiles,ren/dotfiles,ajkamel/dotfiles,prabinv/dotfiles,lannn/dotfiles,koerbcm/dotfiles,bschmoker/dotfiles,bigbam505/dotfiles-work,alexbaldwin/dotfiles,Danielpk/dotfiles,moofish32/dotfiles,ZloeSabo/dotfiles,dainmiller/thoughtbot-dotfile-mods,koerbcm/dotfiles,mspringfield/dotfiles,tchiarato/dotfiles,prabinv/dotfiles,ransingh/dotfiles,aliceyoung9/dotfiles,koerbcm/dotfiles,kkelleey/dotfiles,T1D/dotfiles,ransingh/dotfiles,turino/dotfiles,YepengFan/dotfiles,bschmoker/dotfiles,koerbcm/dotfiles,voanhduy1512/dotfiles,mspringfield/dotfiles,astoellis/dotfiles,ren/dotfiles,bigbam505/dotfiles-work,Danielpk/dotfiles,tchiarato/dotfiles,YepengFan/dotfiles,ransingh/dotfiles,ncuesta/dotfiles,ecnalyr/dotfiles