Since 2013, we have been giving credit to our fellow co-authors when integrating changes in our code bases. This was done by using commit message trailers like this one:
Co-authored-by: FirstName LastName <email@domain.org>
Here are the earliest occurrences of such acknowledgment: commontk/CTK@9aa389d and Slicer/Slicer@43808ca.
What is great is that GitHub now support this too. It will be part of your contribution statistics:
Additionally, we often use trailer like this one:
Thanks: FirstName LastName <email@domain.org>
Reviewed-by: FirstName LastName <email@domain.org>
Suggested-by: FirstName LastName <email@domain.org>