Created faq (markdown)

faq.md

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+## FAQ/Troubleshooting
+
+### Plugins are not installed/updated in parallel
+
+Your Vim does not support Ruby interface. `:echo has('ruby')` should print 1.
+
+In order to setup Vim with Ruby support, you may refer to [this
+page](https://github.com/junegunn/vim-plug/wiki/ruby).
+
+### *Vim: Caught deadly signal SEGV*
+
+If your Vim crashes with the above message, first check if its Ruby interface is
+working correctly with the following command:
+
+```vim
+:ruby puts RUBY_VERSION
+```
+
+If Vim crashes even with this command, it is likely that Ruby interface is
+broken, and you have to rebuild Vim with a working version of Ruby.
+(`brew remove vim && brew install vim` or `./configure && make ...`)
+
+If you're on OS X, one possibility is that you had installed Vim with
+[Homebrew](http://brew.sh/) while using a Ruby installed with
+[RVM](http://rvm.io/) or [rbenv](https://github.com/sstephenson/rbenv) and later
+removed that version of Ruby.
+
+[Please let me know](https://github.com/junegunn/vim-plug/issues) if you can't
+resolve the problem. In the meantime, you can set `g:plug_threads` to 1, so that
+Ruby installer is not used at all.
+
+### Errors on fish shell
+
+If vim-plug doesn't work correctly on fish shell, you might need to add `set
+shell=/bin/sh` to your .vimrc.
+
+Refer to the following links for the details:
+- http://badsimplicity.com/vim-fish-e484-cant-open-file-tmpvrdnvqe0-error/
+- https://github.com/junegunn/vim-plug/issues/12
+
+### Freezing plugin version with commit hash
+
+vim-plug does not allow you to freeze the version of a plugin with its commit
+hash. This is by design. I don't believe a user of a plugin should be looking
+at its individual commits. Instead, one should be choosing the right version
+using release tags or versioned branches (e.g. 1.2.3, stable, devel, etc.)
+
+```vim
+Plug 'junegunn/vim-easy-align', '2.9.2'
+```
+
+If the repository doesn't come with such tags or branches, you should think of
+it as "unstable" or "in development", and always use its latest revision.
+
+If you really must choose a certain untagged revision, consider forking the
+repository.
+
+### Migrating from other plugin managers
+
+vim-plug does not require any extra statement other than `plug#begin()` and
+`plug#end()`. You can remove `filetype off`, `filetype plugin indent on` and
+`syntax on` from your .vimrc as they are automatically handled by
+`plug#end()`.