Git specialist (rather admin than developer) needed for one-time help with chose proper strategy for move changes between 2 repos

I'm managing 2 repositories. Both of them may be on different VCS (for example github and self hosted gitlab). First repo (Repo 1 on attachment) is used by many developers for features development. They creating feature branches and they commits/pushing changes into repo1/master with their own commit messages and all commits are authored by developer name/email. Second repo (repo 2) is "official" repo. I want to merge/pull changes from repo1/master into repo2/master BUT with my own commit message and another author. Other words - in git history of repo1 I want to see entire history including commit authors but in repo2 history I want to see only one author of changes (changes are picked from repo1 master). I would say - i trying to achieve functionality of merging of branches but between 2 completely separated repos (in meantime i want to erase commits history and set my own commit message and author). Searching for GIT specialist who could show me how I can solve my problem and eventually explain me that