Using the slash character in Git branch name

I'm pretty sure I saw somewhere in a popular Git project the branches had a pattern like "feature/xyz".

However when I try to create a branch with the slash character, I get an error:

$ git branch labs/feature
error: unable to resolve reference refs/heads/labs/feature: Not a directory
fatal: Failed to lock ref for update: Not a directory

Same problem for (my initial attempt):

$ git checkout -b labs/feature

How does one create a branch in Git with the slash character?

Are you sure branch labs does not already exist (as in this thread)?

You can't have both a file, and a directory with the same name.

You're trying to get git to do basically this:

% cd .git/refs/heads
% ls -l
total 0
-rw-rw-r-- 1 jhe jhe 41 2009-11-14 23:51 labs
-rw-rw-r-- 1 jhe jhe 41 2009-11-14 23:51 master
% mkdir labs
mkdir: cannot create directory 'labs': File exists

You're getting the equivalent of the "cannot create directory" error.
When you have a branch with slashes in it, it gets stored as a directory hierarchy under .git/refs/heads.

Note that labs must not be an existing branch, as ddruganov points out in the comments:

 git switch -c 19023-commerce/19033-commerce-view 19023-commerce

 # Fails with:

 fatal: cannot lock ref 'refs/heads/19073-commerce-view/99999-test-branch': 
 'refs/heads/19073-commerce-view' exists; 
  cannot create 'refs/heads/19073-commerce-view/99999-test-branch'

As explained in "git push: refs/heads/my/subbranch exists, cannot create":

• If branch b exists, no branch named b/anything can be created.
• Likewise, if branch dev/b exists, dev/b/c cannot be created.

This is a git internal limitation.

It is possible to have hierarchical branch names (branch names with slash). For example in my repository I have such branch(es). One caveat is that you can't have both branch 'foo' and branch 'foo/bar' in repository.

Your problem is not with creating branch with slash in name.

$ git branch foo/bar
error: unable to resolve reference refs/heads/labs/feature: Not a directory
fatal: Failed to lock ref for update: Not a directory

The above error message talks about 'labs/feature' branch, not 'foo/bar' (unless it is a mistake in copy'n'paste, i.e you edited parts of session). What is the result of git branch or git rev-parse --symbolic-full-name HEAD?

I forgot that I had already an unused labs branch. Deleting it solved my problem:

git branch -d labs
git checkout -b labs/feature

Explanation:

Each name can only be a parent branch or a normal branch, not both. Thats why the branches labs and labs/feature can't exists both at the same time.

The reason: Branches are stored in the file system and there you also can't have a file labs and a directory labs at the same level.

Sometimes that problem occurs if you already have a branch with the base name.

I tried this:

git checkout -b features/aName origin/features/aName

Unfortunately, I already had a branch named features, and I got the exception of the question asker.

Removing the branch features resolved the problem, the above command worked.

Branch name is case sensitive and so if there are folders created in Azure by your release manager, folder names should match exactly. Learned it hard way raising it with manager.