rbenv 1.0 发布 Ruby 版本管理工具

rbenv 是个健壮的工具，遵循 UNIX 标准来实现 Ruby 每个项目版本和相关运行时环境的管理。

rbenv 1.0 相比 0.4.0 版本，改进内容如下：

Speed up rbenv with dynamically loaded realpath C extension
Speed up rbenv rehash when there are many Ruby versions with similar sets of executables
Improve performance of rbenv-which for “system” version
Avoid rbenv-exec calling out to rbenv-version-name twice

New plugin hooks version-name and version-origin enable plugin authors to hook into version selection logic.
rbenv versions --skip-aliases --bare will only list versions that are not aliases (symlinks) for other versions.
rbenv version-file <dir> finds a .ruby-version file in the target directory or any of its parent directories.
rbenv init now recognizes and supports fish shell syntax.
rbenv --debug <command> is a shortcut for enabling RBENV_DEBUG.

rbenv local now respects .ruby-version file in parent directories as well
rbenv versions now emits a warning when no Ruby versions were found
Consistently support rbenv <command> --help as alternative to rbenv help <command>
Improve parsing of git revision in rbenv --version when rbenv was installed from git
Export PS4 when RBENV_DEBUG is set for more informative debug output

Fix incorrect formatting of rbenv-help output under MAWK (Ubuntu)
Prefer gawk over awk if both are available
Fix resolving symlinks in rbenv-hooks
Fix iterating through paths that have spaces in them
Fix rbenv rehash when paths have spaces in them
More useful error message when rehash fails on a non-writable directory
Make rbenv-exec fail for invalid Ruby version
Bail out early if readlink is not available
Properly resolve symlinks when listing hook scripts
Better error message for rbenv prefix system
Fix reading .ruby-version on platforms that don’t support process substitution
Remove carriage return characters in .ruby-version files
Fixes rbenv on OpenBSD and other systems that don’t support head -c
Guard against exported CDPATH
Ensure that IFS is reset to its original value within hook scripts