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Git upstream

01 Mar 2017   Git  #git 

Whenever I push my newly created local repository to a remote repo, I am prompted with this message.

fatal: The current branch master has no upstream branch.
To push the current branch and set the remote as upstream, use

    git push --set-upstream origin master

Enough is enough, I have searched about it and I am going to write about it.

What is Upstream?

Upstream is the name of remote branch to which our local branch is synced. Every local branch has exactly one upstream set. Say we have a local branch A and its upstream is set to origin/B, then every push will push the changes to origin/B etc. git branch -vv can be used to print the remote tracking branch.

$ git branch -vv
* master 8061b7f [origin/master] update

Here master branch is tracking origin/master.

Why Upstream?

Setting upstream has effect on many commands e.g. push, pull, merge. When these commands are used without any conditional arguments, remote branch information is retrieved from its upstream. Say, I have created a new repository and added its origin

$ git init test # create a new empty repo
Initialized empty Git repository in F:/Sandbox/gitdemo/test/.git/

$ cd test # move to newly created repo

$ git remote add origin /f/Sandbox/gitdemo/myremote/ # add remote

$ git remote show origin # print remote
* remote origin
  Fetch URL: F:/Sandbox/gitdemo/myremote/
  Push  URL: F:/Sandbox/gitdemo/myremote/
  HEAD branch: master
  Remote branches:
    master    new (next fetch will store in remotes/origin)
    newbranch new (next fetch will store in remotes/origin)

Everything is fine till now. Let’s use pull to fetch data from remote

$ git pull # sync data with remote
remote: Counting objects: 6, done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 6 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (6/6), done.
From F:/Sandbox/gitdemo/myremote
 * [new branch]      master     -> origin/master
 * [new branch]      newbranch  -> origin/newbranch
There is no tracking information for the current branch.
Please specify which branch you want to merge with.
See git-pull(1) for details.

    git pull <remote> <branch>

If you wish to set tracking information for this branch you can do so with:

    git branch --set-upstream-to=origin/<branch> master

See, git pull need to know which remote branch it needs to pull data from. As we haven’t set any upstream yet, git provides us two options.

  • Either use git pull <remote> <branch>, pass everything explicitly to pull command.

OR

  • Set it’s upstream to
git branch --set-upstream-to=origin/<branch> master

next time you don’t need to pass everything. Just use git fetch/status/merge/pull whatever you want.

Let’s chose the first option and see the result.

$ git pull origin master # pull from origin/master
From F:/Sandbox/gitdemo/myremote
 * branch            master     -> FETCH_HEAD

It syncs out current branch with orgin/master but still we haven’t set its upstream we need to write the whole command again if we want to push or fetch. e.g.

$ touch c.txt # create new file c.txt

$ git add . && git commit -m "test" # add to index and commit
[master f1be4b8] test
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 c.txt

$ git push # we haven't set upstream, we need write the complete command (git push <remote> <branch>)
fatal: The current branch master has no upstream branch.
To push the current branch and set the remote as upstream, use

    git push --set-upstream origin master


$ git push origin master # it works with complete command.
Counting objects: 2, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (2/2), done.
Writing objects: 100% (2/2), 258 bytes | 0 bytes/s, done.
Total 2 (delta 0), reused 0 (delta 0)
To F:/Sandbox/gitdemo/myremote/
   8061b7f..f1be4b8  master -> master

$ git branch -vv # SEE! we don't have any remote tracking branch for our current branch yet. I will use same
# command after setting upstream in next command snippet.
* master 8061b7f update

Now let’s try all this with setting upstream first.

$ git branch --set-upstream-to=origin/master master # set upstream to origin/master
Branch master set up to track remote branch master from origin.

$ git branch -vv # confirm master branch is tracking origin/master
* master f1be4b8 [origin/master] test

$ touch another.txt # update working directory

$ git add . && git commit -m "another file" # add to index and commit
[master 0d6cc8a] another file
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 another.txt

$ git push # use just push with any other argument.
Counting objects: 2, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (2/2), done.
Writing objects: 100% (2/2), 238 bytes | 0 bytes/s, done.
Total 2 (delta 1), reused 0 (delta 0)
To F:/Sandbox/gitdemo/myremote/
   f1be4b8..0d6cc8a  master -> master

Upstream for newly created branch

When a new branch is created using (git branch branch-name), it is created locally without having any link to remote. Pushing it to remote will do this

  • Create a new branch in remote repo
  • Add its reference to remote tracking branches locally.

Despite of all this, git does not set any upstream for this local branch. In this case, you can use

git branch --set-upstream-to=origin/new-branch new-branch

I have done the same in above example.

Upstream for cloned repository

Let’s end it with this observation, “whenever I clone a repository, I don’t need to set its upstream. Everything just works fine.”. This is because when I clone a remote repository, git checkouts into master branch and sets master branch to track origin/master.

Push with -u

Another thing that is mentioned when a new repo is created on Github or any other site

# this snippet is copied from github after creating a new repo (demo)

…or create a new repository on the command line

echo "# demo" >> README.md
git init
git add README.md
git commit -m "first commit"
git remote add origin https://github.com/allaudin/demo.git
git push -u origin master # see -u here
…or push an existing repository from the command line

git remote add origin https://github.com/allaudin/demo.git
git push -u origin master # see -u here

In either case, they tell you to use push with -u switch.

git push -u origin master # see -u here

Push -u does one special thing, apart from pushing data to remote, it also sets the upstream for current branch.

Hopefully, next time you will know what’s going on while setting upstream and it will not bother you or me anymore.

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