Git: merge only the changes made on the branch

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  G---H             // Release Branch
 /
/
A---B---E---F---    // master
    \
     \
      C---D---     // bug fix branch

Based on our particular needs for our project, it is quite common for the above scenario to occur. We have our master/dev branch with some commits. Then we get a bug report and start fixing that on the bug branch (commits C and D above). More commits happen in the dev branch in the meantime. Next we are told we need to create a release for a customer which cannot include the changes introduced by commits B, E and F above, but it should include the bug fix.

So we branch off of dev before change B was ever applied, but what is the best way to get the bug fix into this release branch too? If I perform a merge of the branch it will include the change that was made in B which I don't want. I could perform a cherry-pick of commits C and D but I read that cherry picking is not always a good idea based on this answer basically because my repo would then look like:

  G---H---C'---D'--- // Release Branch
 /
/
A---B---E---F---     // master
    \
     \
      C---D---       // bug fix branch

So C' and D' appear as completely new commits with different sha-1 IDs as C and D. Is this really a bad thing? What problems can this lead to? Is there a better way of getting the changes from the bug fix branch into the release branch?

git-branch branch merge version-control git
4 Answers

Create a patch file containing the unique content from the bugfix branch. Then apply that patch file to the release branch.

Example:

> git checkout bugfix_branch
> git diff B HEAD > unique_changes.patch /* where "B" is the point where bugfix_branch split from dev */
> git checkout release_branch
> git apply unique_changes.patch

Et voila! You now have only the unique changes from the bugfix branch in your release branch. Note that format-patch tends to more gracefully handle situations where files have been moved or deleted, so you may need to play around with the actual process by which the patch is generated, but this approach should get you close.

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