In every project I've worked on, the preferred form for making changes is actually files in a filesystem. I've also seen projects where the preferred form is a particular IDE's configuration. Unless you've got a compiler that builds object files out of git and a build process that uses multiple commits to generate the output, git is the medium of transfer, not the form of the work.
That said, you may well have a build process that generates srpms out of git repositories. If you imagine a project whose goal is to package the Linux kernel, and whose developers work to produce a git repository with an "origin" branch and a HEAD, and, in addition to this git repository, they have a build system which produces packages containing an origin tarball, a set of patches, a changelog, and scripts to apply the patches, the git repository is part of their source. On the other hand, the project need not be under the GPL just because the kernel is, any more than the kernel being under the GPL requires compilers that compile it to be under the GPL. And the GPL doesn't mean that I can insist that RMS loan me his computer to work on gcc with.
To my knowledge, there are no distro-maintenance projects that actually function like that, in part because such a project would have a hard time finding a version control system that could handle it; to my knowledge, there aren't any version control systems that handle repositories as revision contents, without getting confused and trying to handle the revision contents of the repositories as the revision contents. In order to keep them straight, metaprojects either aren't stored in revision control, or they track patch series (possibly preparing commits using a version control system applied to the project they package, which may be a common resource or may be individual and not in any way official).
Kuhn: Thoughts On GPL Compliance of Red Hat's Linux Distribution
Posted Mar 12, 2011 20:55 UTC (Sat) by ballombe (subscriber, #9523)
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Debian has a system (git-buildpackage and svn-buildpackage) that generates a source packages from a git or SVN repository by converting commit in the Debian branch to a quilt series, and updating the changelog. The Debian kernel is packaged that way.
Kuhn: Thoughts On GPL Compliance of Red Hat's Linux Distribution
Posted Mar 13, 2011 0:28 UTC (Sun) by vonbrand (subscriber, #4458)
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No, this is nonsense. For, e.g., Ubuntu people (who use bzr, not git) or others who just don't like VCS this isn't exactly "preferred". Also, if I happen to hack on my program by keeping XEmacs buffers open on each file, do I have to distribute the memory image of the editor?