I was looking for a simple git client app inside nextcloud (something similar to the stopped project GitHub - klaussilveira/gitlist: An elegant and modern git repository viewer), but apparently that does not exist (yet).
Then I found this discussion and I am a bit confused about it: is it about setting up a git server or about working on files that are inside a git repository?
Setting up a git server is quite trivial (at least, if you have command line root access to the host) and needs to be done only once; and therefore not a case for an app in my opinion. What other regular tasks would you want to do through this app?
Working on the content of a git repository is much more complicated, depending on what you want to do. Simple browsing of files and histories and displaying metadata like commit comments should be ok, I guess (that is for example what the above mentioned gitlist application does), but modifying, committing, merging, branching etc. is quite complex and there are interfaces like gitlab who do that very well. Any nextcloud app could never reach that level of sophistication.
In my opinion, a read-only graphical interface with a feature set similar to gitlist, along with the possibility to initialise bare repositories which can be filled by any git client on your local PC would be perfect. Is that what you meant, too?