CODEWITHSUNDEEP
gitmergemerge-strategy
tanager
tanager

Reputation: 189

How can I merge changes which git believes it already has (due to 'strategy ours' merge)?

We have two branches A and B. For a while, all commits to B were being automatically merged into A by a backend process. At some point, we switched directions, now merging A commits into B. When the switch occurred, we did a git merge --strategy=ours so that B would believe it had all content from A and only new content should actually be merged. Whether or not this was correct, it is done.

Now, we need to merge all content from A into B, but various git commands tell me there is no missing content. This makes sense, given the 'strategy' merge.

How should I approach this problem? Here are a few things I am exploring, where nothing is quite working as I hoped it would.

  1. Create a new branch, A', based on the same commit that A was created from. Play every commit from A into A' using cherry-pick. Now I have a new branch A' with a whole new set of SHAs, so I could merge it into B. One problem with this approach might be that many (30%) of the commits on A are merge commits. My first attempt using this idea, and cherry-picking only the first commit from A, did not produce what I expected.
  2. Create a diff and then use git apply. The entire set of changes in A is very large, so I tried doing this by first generating a diff of only one logical set of changes (from tag 1 to tag 2 on A). When I try to apply it, I get lots of 'patch does not apply' messages.

Is there any way to tell git to merge even though it has already been told the commit has been merged? I don't mind writing a script if a manual approach is the best. (We have 111 tags on branch A. At a minimum, the ones which occurred before the switch in merge direction need to be merged to B.)

Thanks for any advice.

Upvotes: 0

Views: 38

Answers (1)

eftshift0
eftshift0

Reputation: 30277

If you want to do a merge that makes B just like A, you can do:

git checkout B
git merge --no-commit A
git restore --source A -- .
git merge --continue

Voila! Check with git diff A and it should be empty.

If git complained because there is nothing to merge, that means that A is already merged (it's tip) into B.... So you could run a restore just like the one I used there and then a commit so that B looks exactly like A or you could create a new empty commit in A and then follow the recipe I posted there from the beginning or (the hackish way) you could force creating a new commit out of thin air that has B and A as parents and A's tree like this:

git commit-tree -p B -p A -m "a merge commit out of thin air" A^{tree}

That will print the ID of a commit that is just what you want.... Check its history and contents and if you like it, merge that commit ID into B.

Upvotes: 0

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