How to 'git remote add' and track a branch in the same filesystem

I have 2 local git archives in /a and in /b which were cloned from remotes/origin.

There is a new branch z on /b

How can I track and fetch branch z from archive /a ?

I tried this:

cd /a
git remote add b /b

This creates 2 config entries, but I did not manage to fetch something or to list remote branches on /a that would show the branches on /b

After trying different things I found the following that works:

1) git remote show b lists all the remote branches in b

2) I can fetch using this syntax:

git fetch file:///a/ z

Other things that also work:

$ cd /b
$ git checkout -b z
Switched to a new branch 'z'
$ git pull b z

But those commands still dont work and I cannot understand why:

git branch -a 

does not list the remote branches in b (onlz the ones in origin are shown)

git checkout -t b/z

Does not checkout anything but returns an error message

So far you've only added b as a remote. You can try git branch -a to list your remote branches after you've fetched them.

Here's the commands to checkout the z branch from b:

git remote add b /b              # you've already done
git fetch b                      # get it so we can see it
git checkout -t b/z              # check out a local tracking branch

The -t (or --track) creates a tracking branch, otherwise you'll be in detached head state.

Then you should see:

/a$ git branch
  master
* z

For anyone unclear on the steps involved, here's what I did:

create origin

$ mkdir origin
$ cd origin/
/origin$ git init --bare
Initialized empty Git repository in /origin/
/origin$ cd ..

clone 'a' and add some content

$ git clone origin/ a
Initialized empty Git repository in /a/.git/
warning: You appear to have cloned an empty repository.
$ cd a
/a$ echo hi there > hello
/a$ git add hello
/a$ git ci -m'first commit'
[master (root-commit) 0867b93] first commit
 1 files changed, 1 insertions(+), 0 deletions(-)
 create mode 100644 hello
/a$ git push origin master 
Counting objects: 3, done.
Writing objects: 100% (3/3), 210 bytes, done.
Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
To /origin/
 * [new branch]      master -> master

clone 'b' and add more content on new branch

/a$ cd ..
$ git clone origin/ b
Initialized empty Git repository in /b/.git/
$ cd b
/b$ git checkout -b z
Switched to a new branch 'z'
/b$ echo new guy reporting in >> hello 
/b$ git ci -am "new recruits"
[z 81044ee] new recruits
 1 files changed, 1 insertions(+), 0 deletions(-)

Add 'b' as a remote to 'a'

/b$ cd ../a
/a$ git remote add b ../b
/a$ git fetch b
remote: Counting objects: 5, done.
remote: Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
From ../b
 * [new branch]      master     -> b/master
 * [new branch]      z          -> b/z
/a$ git br
* master
/a$ git checkout -t b/z
Branch z set up to track remote branch z from b.
Switched to a new branch 'z'
/a$ git br
  master
* z

I've put the above commands into a script so you can test it out yourself.

I don't think you can do that.

I think you'll need to push branch z to origin in b and fetch it from a.

cd /b
git push origin z

That last command pushes local branch z to remote (so pushing z -> origin/z)

then you can track it locally in repo a:

cd /a
git checkout -b z origin/z

That last command creates (and checks out) a local branch z that tracks origin/z