When `rbenv --version` is called, this now happens:

1. It changes into the directory where `libexec/rbenv--version` resides
   and checks if it's a checkout of the rbenv repo (as opposed to
   Homebrew checkout or something else). Then it reads the git revision.

2. If that failed, change to `$RBENV_ROOT` directory and repeat step 1.

Use `command` to run rbenv rehash

Closes #529

If set by the user's environment, `git config --global` writes will go
to that destination instead of temporary $HOME. We definitely don't want
that.

Fixes #742

rbenv-init: do not use basename for $shell

Include gems dir in .gitignore

Closes #725

Display version origin with non-installed versions

This is useful as an indicator where it is coming from.

Provide uninstall instructions in the README

It's not that this is a preferred way to set a global version (one
should use `rbenv global <version>` instead), but this fixes the
function purely for correctness: all parent directories should be
scanned, even the root directory.

Fixes #745

This can be done using bash directly.

Fix test for adding shims in fish

Commit e2173df4 (for issue #369) did not handle the fish test properly.

This renames it and fixes the assertion.

Closes #699, fixes #666 [ci skip]

Fix pattern replacement to allow flags with commas.

Remove dead links to History and License from README

Cfr. #688

Remove history, license information from README

Remove warning about extraneous "ruby-" prefix in `.ruby-version`

Update README to make rbenv version consistent with previous `versions` output

The `rbenv versions` info highlights 1.9.3-p327 as the current version, and
making `rbenv version` sample output match that helps make it clearer.

[README] Updated link to bundler.io

The license information is already present in the LICENSE file.

We won't maintain it anymore. Instead, the changelogs can be obtained
from the project's Releases page: https://github.com/sstephenson/rbenv/releases

When we started to support reading `.ruby-version` files, we made a
commitment to not support fuzzy version matching. Treating "ruby-2.1.5"
as "2.1.5" is a sort of fuzzy matching, so we put in place a warning
telling you to remove the extraneous "ruby-" prefix popularly used by
other Ruby version managers to denote MRI. (Their logic is that MRI is
"ruby" and other rubies are not "ruby", apparently.)

However, people are often not able to remove the prefix in their
projects because they want to support other coworkers and tools that
sadly still require the prefix, like RubyMine.

So to restore sanity for a big portion of our users, the warning is gone.

Since communal-gems is maintainer-approved, thought it would be useful to include the directory it uses in the ignore list.

(This also helps me, since I install rbenv as submodule and without this entry, the submodule is perpetually marked dirty.)

In the event that `eval "$(rbenv init -)"` is called from a function named
rbenv (which I do to get rbenv to load lazily in my shell), evaluating the
phrase `rbenv rehash` will cause the outer function to run again (causing an
infinite loop).

This change makes it clear you want the command named rbenv and not a function
which may exist in the environment.

As it seems, JRuby 1.7 complains on stderr every time you invoke `system`:

    warning: executable? does not in this environment and will return a dummy value

It doesn't seem to complain when backtics are used. It's safe to use
backticks here because `rbenv rehash` doesn't output anything on stdout,
and the exit status of the command is irrelevant.

Bring rbenv-gem-rehash functionality to core

This bakes in the functionality of rbenv-gem-rehash plugin.

The Rubygems hook is improved:

- It will not rehash for gems installed in locations that rbenv otherwise
  doesn't search for binstubs; for instance in case of
  `bundle --path vendor/bundle`.
- It rescues exceptions and makes them non-lethal by warning on stderr.

This allows rbenv source code to ship with built-in hooks.

Speed up `rbenv rehash`

Speed up rbenv by dynamically loading compiled command

It doesn't need to be a bash array and we don't need a separate index of
shims registered. Simply keep everything in a space-separated string and
use that as an index as well.

This assumes that executable names *never* have spaces in them.

On my system that has 25 versions under rbenv, this speeds up rehash
almost 3-fold:

- before: 391 ms
- after:  134 ms

This is achieved by removing duplicate names of executables before
registering them as shims. Since most Rubies will share a lot of the
same executable names ("ruby", "rake", "bundle", ...), this is a
considerable reduction in number of shims registered.