How to create a single commit with the differences between the local and remote Git repositories?

Question

In Git, let's say I've been working on a local branch:

  Common ancestor      
        /\
       A  \
      /    X
     B      \
    /        Y
   C       remote
 local

I made local commits A, B and C and in the mean time the remote branch moved on with commits X and Y. So I do a pull and get:

  Common ancestor      
        /\
       A  \
      /    X
     B      \
    /        Y
   C        /remote
    \      /
     \    /
      \  /
       \/
       M
     local

If I now push, the remote history will include all my A, B, C and M commits... but this isn't what I want.

I want to just push a single commit with the differences from my local branch so the remote branch will just look like this with none of the merging complexity:

  Common ancestor      
         \
          \
           X
            \
             Y
              \
               N
             remote

How can I achieve this?

Answer 1

Do a

git pull --rebase

Which is equivalent to git fetch and a git rebase instead of a git merge.

Answer 2

Just merge the local changes into the remove ones to get the N commit:

1. Create, checout a branch remote_n locally, and pull all data from remote's master into the remote_n branch:

   git branch remote_n
   git checkout remote_n
   git pull origin master
   

2. Do a merge of master's HEAD into remote_n, fix inconsisences, and commit changes, so you will get the single N commit (by using --squash option):

   git merge --squash master
   vim ...
   git add .
   git commit
   

3. Push the result N commit into remote's master branch:

   git push remote master
   

NOTE: You will get the local remote_n branch as a new master branch for your repo.

If you really need to avoid the merge do manually something like:

1. Get diff of Common, and C commits:

   git diff Common_sha C_sha > common_c.diff
   

2. Reset tree down to Common commit, pull remote changes, apply the diff, and commit it:

   git reset --hard Common_sha
   git pull remote master
   git apply --ignore-space-change common_c.diff
   git commit
   

3. Push the result N commit into remote's master branch:

   git push remote master
   

NOTE: this model don't take into account binary files that can't be displayed by git diff.