I use RVM all the time when I develop Ruby (and Rails) applications. It’s great for isolating Ruby environments and gem packages for a specific project. I also use git extensively – especially branching when developing new features for an app.
Sometimes a branch works with new gems, that I do not want to pollute my main project-specific gemset with. So I create a new RVM gemset for this particularly branch. This has had its own problems because a “git checkout” now also needed to be followed by a “rvm use” statement. Also having a .ruby-gemset file in the project root led to RVM resetting the current gemset as soon as I changed directory.
One solution could be to check-in the .ruby-version/.ruby-gemset files in each branch, but I don’t want to annoy fellow developers with my RVM files. So I came up with the solution below instead.
First for this example, I assume that you have a git repository containing a master branch and another branch. If not, here’s a quickstart to make this happen:
$ mkdir myproject && cd myproject $ git init . $ touch 1.txt $ git add -A $ git commit -m 'First master commit' [master (root-commit) b578056] First master commit 2 files changed, 2 insertions(+) create mode 100644 .gitignore create mode 100644 1.txt $ git checkout -b somebranch Switched to a new branch 'somebranch' $ touch 2.txt $ git add -A $ git commit -m 'First somebranch commit' [somebranch d10e2c1] First somebranch commit 1 file changed, 0 insertions(+), 0 deletions(-) create mode 100644 2.txt $ git checkout master Switched to branch 'master' $ git branch * master somebranch
Okay with that squared away, let’s get on with the actual steps. You need to create a RVM gemset for each branch (master and somebranch) with the appropiate .ruby-version/.ruby-gemset files. The principle is, that you rename them, so they have a postfix named after the branch.
First create for the master branch:
$ rvm --create --ruby-version 2.0.0@myproject-master ruby-2.0.0-p643 - #gemset created /home/carsten/.rvm/gems/ruby-2.0.0-p643@myproject-master ruby-2.0.0-p643 - #generating myproject-master wrappers.......... $ ls -a . .. .git .ruby-gemset .ruby-version
Then rename the files:
$ mv .ruby-gemset .ruby-gemset-master $ mv .ruby-version .ruby-version-master $ ls -a . .. .git .ruby-gemset-master .ruby-version-master
Now do the same for the branch “somebranch”:
$ rvm --create --ruby-version 2.0.0@myproject-somebranch ruby-2.0.0-p643 - #gemset created /home/carsten/.rvm/gems/ruby-2.0.0-p643@myproject-somebranch ruby-2.0.0-p643 - #generating myproject-somebranch wrappers.......... $ ls -a . .. .git .ruby-gemset .ruby-gemset-master .ruby-version .ruby-version-master $ mv .ruby-version .ruby-version-somebranch $ mv .ruby-gemset .ruby-gemset-somebranch
Since the files are renamed as shown, they will not by themselves trigger an RVM gemset switch, if you enter the directory.
If you look at your git repo now, you will see the files as untracked.
$ git status On branch master Untracked files: (use "git add..." to include in what will be committed) .ruby-gemset-master .ruby-gemset-somebranch .ruby-version-master .ruby-version-somebranch nothing added to commit but untracked files present (use "git add" to track)
As stated in the beginning, we don’t want these files in the repository, so create a .gitignore file and add this:
.gitignore
.ruby-version* .ruby-gemset*
Now comes the fun part. We are going to make a hook in our git config. Create this file
.git/hooks/post-checkout
#!/bin/sh # Find current branch name BRANCH=`git rev-parse --abbrev-ref HEAD` # Copy branch-specific RVM files, if available - default to master-branch if [ -f .ruby-gemset-$BRANCH ]; then cp -f .ruby-gemset-$BRANCH .ruby-gemset else cp -f .ruby-gemset-master .ruby-gemset fi if [ -f .ruby-version-$BRANCH ]; then cp -f .ruby-version-$BRANCH .ruby-version else cp -f .ruby-version-master .ruby-version fi
And make sure, that the file is executable, since it is just a script:
chmod +x .git/hooks/post-checkout
After you have done this, everytime you checkout a branch, this script will be called. If you checkout somebranch, it will look for a .ruby-version-somebranch and .ruby-gemset-somebranch and copy them to .ruby-version and .ruby-gemset respectively. If you create a new branch but do not make a specific gemset for this branch, the script will instead copy .ruby-version-master/.ruby-gemset-master. So always as a minimum create these.
You might think that now you a all done. However if you try to checkout a “somebranch” now, things will seem strange. The .ruby-gemset file will be an exact copy of .ruby-gemset-somebranch, but if you call “rvm current”, you will still be on the master gemset. Why is this so?
The thing is: .ruby-gemset is now placed correctly, but will not be read by RVM until you change into the actual directory. Try this:
$ git checkout somebranch Switched to branch 'somebranch' $ rvm current ruby-2.0.0-p643@myproject-master <== Not what we expected $ cd . $ rvm current ruby-2.0.0-p643@myproject-somebranch <== Much better
But this is still an extra manual step, that complicates things. You WILL forget this at some point, so let's get rid of it.
You need to edit your $HOME/.bashrc file and add this line:
$HOME/.bashrc
git () { /usr/bin/git "$@"; cd .; }
This changes the git command to a function, which calls the executable git in /usr/bin with all arguments, and afterwards does the otherwise harmless "cd ." which will then make RVM reload the .ruby-version/.ruby-gemset files.
Exit the shell and open a new to reload .bashrc, and you're good to go.
Please let me know, if you have any trouble with the above. Everything has been tested, but evil typos may have creeped into the text.
Have fun!