I have one repository with a library.
I have another repository with a service, which uses library, but does this by embedding this library instead of using it as a dependency.

Today library in service repository is seriously outdated, we want to sync the code and get rid of the first repository and end up with having 2 different builds (for service and library).

I want to retain the commit history and not just have a single commit made by me, so basically I want to merge commits made to one file in the first repository to a second, which has completely different history. Is this poossible? If so, how can I do this?