I have a repo set up on GitHub, with a Dev branch, which I clone to my local machine using:
git clone https://github....
I then switch to my Dev branch using:
git checkout -b Dev
I then pull just to make sure all is up to date
git pull origin Dev
I am now in my Dev branch, write some code and add the files using:
git add filename
I then commit using:
git commit -m "message"
I then push using:
git push origin Dev
This works all good. A second user then comes along and enters some code. At the same time I am working on a separate file but we are working on the same branch. I add and commit as before. However, when I try to push, I receive the following:
To
https://github.com/ex/ex.git! [rejected]
Dev -> Dev (fetch first) error: failed to push some refs to 'https://github.com/ex/ex.git' hint: Updates were rejected because the remote contains work that you do hint: not have locally. This is usually caused by another repository pushing hint: to the same ref. You may want to first merge the remote changes (e.g., hint: 'git pull') before pushing again. hint: See the 'Note about fast-forwards' in 'git push --help' for details.
I do as it says and perform:
git pull origin Dev
I can then push as before and all seems well. However, back on GitHub when I check the commit history I see this:
Merge branch 'Dev' of https://github.com/ex/ex into Dev
amongst the commits I just added. Why is this merge happening? How can I stop this from happening?
The merge was needed because you and your second user diverged; each of you committed something off of a common base. Getting back in sync requires combining the two development paths.
A 'merge commit' does no harm whatsoever; it really isn't worth worrying about it. However, if you want to avoid it, often to keep a cleaner history, you perform:
git pull --rebase ...
which will rebase your new commits onto whatever is pulled from the repository. The history will then appear linear.
Here is an example. A repository with two branches:
$ git log --oneline --graph --all
* 678ea83 c
| * 2c1e48f b
|/
* 5836f6f a
The result of merge:
$ git merge dev
Merge made by the 'recursive' strategy.
0 files changed
create mode 100644 b
$ git log --oneline --graph --all
* 6d50134 Merge branch 'dev'
|\
| * 2c1e48f b
* | 678ea83 c
|/
* 5836f6f a
Alternately, the result of rebase:
$ git rebase dev
First, rewinding head to replay your work on top of it...
Applying: c
$ git log --oneline --graph --all
* 89a3771 c
* 2c1e48f b
* 5836f6f a