git pull conflicts when pulling a non current branch

Question

I have a problem when manipulating git pull. Consider I have 2 branches on my remote (origin) repository : A and B.

The remote B branch is ahead of the local B branch by 1 commit.

This additional commit (on the remote B branch) just add a new file, say "newfile".

In my local branch A, I have a file "newfile" and its content is different from the one of the remote B branch.

Then, I run this commands:

git checkout A
git pull origin B:B

I can see the following behavior: the branch B is updated as I expected. B has been fast-forwarded, and then contains "newfile". But I also have a conflict on "newfile". and in my current directory, the file "newfile" contains the conflicts markers.

Why is there a conflict while the merge has already been done ?

Thank you.

Answer 1

When you do a pull, (by default) it gets everything that it can without overwriting any changes you have made. Anything that it could not get because it would have had to modify your edit is considered a conflict. Conflicts need to be resolved manually, or you can undo your changes and do another pull. Once you complete your merge, you can do a push to commit your change.

This is the default behavior because think of how bad this could be if it didn't do this- your changes could be blown away by a pull without your permission.

Answer 2

I think I misunderstood the semantics of git pull. I thought that :

git pull origin B:B

meant :

fetch the remote B 
         + 
merge the remote B into the local B

I realize that it means :

fetch the remote B and updates (if fast-forward is possible)  the local B
             +
merge the remote B into the local branch

In fact git pull will always make its merge into the local branch, independently of the refspec.

In other words, pull = fetch + merge. The update of the local B branch is done by "fetch", and the conflict is generated by the following merge operation (into the local branch).