Managing Dotfiles With Git

Managing so-called “dotfiles” (config files starting with a . in your home directory) in git is a fairly common practice. There are many write-ups on this topic already, but I wanted to share my own workflow as well as some potentially useful tips and tricks.

For those unaware, dotfile management basically consists of adding files such as your .vimrc, .tmux.conf or other files in a git repository so that you can both track changes in these files over time as well as share them across multiple computers. If you have a home laptop and a work computer, you can ensure you have the same setup on both by keeping your files in a git repository that is synchronized on both machines.

There are a few common strategies for doing this. Perhaps the simplest (and the method I used for quite a while) is to keep all of the files in a separate directory and symlink them into your home directory. For example, you might have a directory called .dotfiles in your home directory that contains your .vimrc file and symlink it into your home directory using

$ ln -s ~/.dotfiles/.vimrc ~/.vimrc

The advantage of this approach is that it allows you to use any file naming and organizational scheme you want. You can keep all files related to Vim in a vim directory and all files related to a program called foo in a separate foo directory. As long as the symlink is in the right place with the right name, it doesn’t matter where it is in your git repo.

A second approach, which I now use, is to use your home directory as the git repository and manage the files directly. Atlassian has a good write up on this method. My setup is almost identical to the one explained in that article, with the exception that I clone my git repo to .dotfiles instead of .cfg and instead of using a separate cfg alias to manage my dotfiles repo, I simply created a wrapper shell function that behaves differently if I am in my home directory:

git() {
	if [ "$PWD" = "$HOME" ]; then
		command git --git-dir="$HOME/.dotfiles" --work-tree="$HOME" "$@"
	else
		command git "$@"
	fi
}

What I like most about this method is how easy it is to bootstrap a new machine with your dotfiles repo:

$ git clone --bare [email protected]:gpanders/dotfiles .dotfiles
$ git --git-dir=$HOME/.dotfiles --work-tree=$HOME checkout -f

You’ll also probably want to set the status.showUntrackedFiles config option to no so that git status doesn’t list all of the untracked files in your home directory.

I use many different computers on a day-to-day basis. I have a personal laptop, a work laptop, and a work desktop, as well as multiple servers that I often SSH into. In my dotfiles repository, I keep all of the files that I want to use across all of my machines in the master branch, and on each individual machine I create a new branch that contains commits that are specific to that machine. For example, on my work computers I add my work email into my mutt and mbsync configurations, which I do not want on my other machines. Changes that I want to propagate across all of my different computers get committed onto master and then I simply rebase my machine-specific branch onto master.

What is the best method for adding a commit to master while on the machine-specific branch? The simplest and naïve approach is to simply checkout the master branch, add and commit the changes, checkout the machine branch, and then rebase:

$ git checkout master
$ git add file1 file2
$ git commit -m "Updated file1 and file2"
$ git checkout machine
$ git rebase master

This is not ideal. Not only is it rather cumbersome, it also can introduce a lot of friction if there are conflicts between the modified files in your machine-specific branch and master, requiring you to first do a git stash before git checkout, followed by a git stash pop and resolving any conflicts that occur. Instead, we can create the commit directly on our machine-specific branch, and then just copy it on to master after the fact:

$ git add file1 file2
$ git commit -m "Updated file1 and file2"
$ git checkout master
$ git cherry-pick machine
$ git checkout machine
$ git rebase master

This can also be nice for creating multiple commits all at once:

$ git add file1 file2
$ git commit -m "Updated file1 and file2"
$ git add file3
$ git commit -m "Updated file3"
$ git checkout master
$ git cherry-pick machine~2..machine
$ git checkout machine
$ git rebase master

This is what I did for a long time. I even smashed it all together into one single, long command that was conveniently saved in my shell history so that I didn’t have to keep retyping it.

This is still not perfect though. Every time you change branches in your dotfiles repository, the config files for your programs change. This can be annoying or even cause problems for programs that live reload when they detect a change in their config file. Therefore, we would ideally like to be able to commit changes onto master without ever having to leave the machine-specific branch.

Enter the interactive rebase.

In case you’re not aware, the interactive rebase is the single greatest tool git provides. It is extraordinarily powerful, and learning and becoming comfortable with this tool will actually change your life. Check out the chapter in the Git book for more info.

What we’ll do is create our commits on our machine-specific branch as before, then use interactive rebase to move them to the “bottom” of the machine-specific branch, then update the master pointer to point to the last of those commits. This will make more sense in picture form.

Before making any changes:

[ C1 ] <- machine
   |
[ C2 ]
   |
[ C3 ]
   |
[ C4 ] <- master

Now, while still on the machine-specific branch, we create the commits that we want to put on master (represented as commits M1 and M2 in the diagram below):

[ M1 ] <- machine
   |
[ M2 ]
   |
[ C1 ]
   |
[ C2 ]
   |
[ C3 ]
   |
[ C4 ] <- master

Now we run

$ git rebase -i master

which brings up the following in your editor:

pick C3 Commit message for C3
pick C2 Commit message for C2
pick C1 Commit message for C1
pick M2 Update file1 and file2
pick M1 Update file3

We modify this in our editor to move the last two lines (commits M1 and M2) to the top of the stack, and then add an exec line to update the master branch:

pick M2 Update file1 and file2
pick M1 Update file3
exec git branch -f master
pick C3 Commit message for C3
pick C2 Commit message for C2
pick C1 Commit message for C1

Save and close the editor, and done! Now the commits are on master and we never had to change our current branch.

The files in the work tree are still modified during the rebase, however. I haven’t yet figured out a way around this, but if I do I will update this post.

We can of course also push master up to the remote:

$ git push origin master:master

And we can also update master with any changes that were pushed from another machine:

$ git fetch origin master:master
$ git rebase master

This describes my workflow with how I manage my dotfiles. If you’re not used to using rebase, it might seem a little daunting at first. But I assure you that once you get used to it it takes no time at all and becomes just another git operation.