How can I set up the working directory and the local repository on different drives?

Question

In Git, how can I set up the working directory and the local repository on different drives? The reason being to back up code on every local commit.

We employ a gatekeep

Answer 1

Use git init's --separate-git-dir flag

The git init command has a flag for that:

--separate-git-dir=<git dir>

Instead of initializing the repository as a directory to either $GIT_DIR or ./.git/, create a text file there containing the path to the actual repository. This file acts as filesystem-agnostic Git symbolic link to the repository.

Example

For this example, let's assume that /Volumes/My_USB/ is the path to a USB drive. (/Volumes is specific to Mac OS, but, other than this path, this example translates to other operating systems in a straightforward manner.)

To initialise a Git repository

• whose working tree is the current directory,
• whose "git directory" is /Volumes/My_USB/projectA_gitdir,

simply run

git init --separate-git-dir="/Volumes/My_USB/projectA_gitdir"

To fix ideas,

• inspect the contents of the .git file:

  $ cat .git
  gitdir: /Volumes/My_USB/projectA_gitdir
  

  As you can see, it's just a text file containing the path to the git directory of your repo.

• inspect the config of your local repo, by running

  $ git config --local --list
  

  You should notice a line that isn't normally present when a repo has been initialised without the --separate-git-dir flag:

  core.worktree=<pwd> 
  

  where <pwd> is the path to the current directory.

• inspect the contents of the git directory; if everything went well, a folder called projectA_gitdir must have been created on the USB drive and populated with everything that normally goes into the .git folder:

  $ ls /Volumes/My_USB/projectA_gitdir
  HEAD        description info        refs
  config      hooks       objects
  

  All good :)

Of course, you will only be able to run Git commands on this repo if the drive is accessible. For instance, after unmounting it, here is what happens:

$ git status
fatal: Not a git repository: /Volumes/My_USB/projectA_gitdir