每当我跑步时，rails s我都会得到：
在任何来源中都找不到 multi_json-1.11.0 尝试运行
bundle install。
bundle install依次运行给我：
Fetching source index from https://rubygems.org/
Updating git://github.com/rails/activerecord-session_store.git
fatal: Refusing to fetch into current branch refs/heads/master of non-bare repository
Retrying git fetch --force --quiet --tags 'git://github.com/rails/activerecord-session_store.git' "refs/heads/*:refs/heads/*" due to error (2/3): Bundler::Source::Git::GitCommandError Git error: command `git fetch --force --quiet --tags 'git://github.com/rails/activerecord-session_store.git' "refs/heads/*:refs/heads/*"` in directory /usr/local/rvm/gems/cache/bundler/git/activerecord-session_store-cf0cfe22b7614cc4fcd416e139ff2bd62ebd6f1d has failed.
If this error persists you could try removing the cache directory '/usr/local/rvm/gems/ruby-2.1.2@global/cache/bundler/git/activerecord-session_store-cf0cfe22b7614cc4fcd416e139ff2bd62ebd6f1d'
fatal: Refusing to fetch into current branch refs/heads/master of non-bare repository
Retrying git fetch --force --quiet --tags 'git://github.com/rails/activerecord-session_store.git' "refs/heads/*:refs/heads/*" due to error (3/3): Bundler::Source::Git::GitCommandError Git error: command `git fetch --force --quiet --tags 'git://github.com/rails/activerecord-session_store.git' "refs/heads/*:refs/heads/*"` in directory /usr/local/rvm/gems/cache/bundler/git/activerecord-session_store-cf0cfe22b7614cc4fcd416e139ff2bd62ebd6f1d has failed.
If this error persists you could try removing the cache directory '/usr/local/rvm/gems/ruby-2.1.2@global/cache/bundler/git/activerecord-session_store-cf0cfe22b7614cc4fcd416e139ff2bd62ebd6f1d'
fatal: Refusing to fetch into current branch refs/heads/master of non-bare repository
Git error: command `git fetch --force --quiet --tags
'git://github.com/rails/activerecord-session_store.git'
"refs/heads/*:refs/heads/*"` in directory
/usr/local/rvm/gems/cache/bundler/git/activerecord-session_store-cf0cfe22b7614cc4fcd416e139ff2bd62ebd6f1d
has failed.
If this error persists you could try removing the cache directory
'/usr/local/rvm/gems/ruby-2.1.2@global/cache/bundler/git/activerecord-session_store-cf0cfe22b7614cc4fcd416e139ff2bd62ebd6f1d'
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