How to merge branches in a repository?

Question

git

It was decided to merge the developer branches in one place. The following dances with a tambourine were done: An empty repository was created, the current state of the project was put into it, updates from the programmer were poured on top, now you need to upload the layout designer updates here. BUT forked the programmer's project, how to send its commit to this new (merged) repository? A branch has been created for it, I read that somehow through diff you can strictly calculate its changes, but how to do it without a clue.

Answer 1

kill everything and business. what is the problem?
there is also git-filter-branch for completely running cases.