I'm just writing a flatpak manifest for SourceGit. After I test it, I'll ask for permission to submit it on flathub

Edit: after a quick look, there have been some issues with flatpak (#462), however it has been almost a year since there was last activity... I'll try it anyways

Update:

I managed to get a successfull Flatpak build (https://github.com/MicrogamerCz/flathub/tree/sourcegit-submission for those who want to try it out), unfortunately it needs access to home directory. This branch was created and pushed from gitsource itself and clone and push via ssh works as well (tested it by updating AUR package and pushing the changes)
(The flatpak manifest and data are on my flathub submission repo, even the branch has the name, but I'm not going to submit it without permission from maintainer/s)

This is a good effort, but I don't know if you read about previous attempts and why they failed well. Your Flatpak lacks LFS and GnuPG signing. Does "open terminal" feature work properly? Don't get me wrong, I support your initiative, but there's a bit more to look into.

LFS should be working, I use org.freedesktop.Sdk as the runtime so that the bundled git and git-lfs can be used. I'm not sure about GnuPG signing, I haven't used that at all yet and "open terminal" shouldn't be difficult to implement, you can run anything (that doesn't require root access) from flatpak via flatpak-spawn --host <command>. I'll try to implement it tomorrow

Update (I haven't had much time to work on it, so it took longer)

LFS works on flatpak (LFS push (even on system) is currently broken, because it doesn't specify branch when pushing to remote origin, fixed it in my fork)

Open terminal also works

Just the GnuPG signing, which I have to learn how to do
(which also should work as it's also a part of org.freedesktop.Sdk)