Optimize Git Repo – Handling Large Binary Files

For this kind of work, I suggest you to learn about Maven which deals with dependency compatibility (among a lot of other things).

With Maven, you could for example use one of these two ways:

Either the "standard" way: by creating a Nexus repository which you will feed with a compiled jar of each version of your common package and to fully exploit maven/nexus the version(s) of JDBC you use. Each time you build your project from any commit, the versioned config file will be read and will use the good revision of your library "common".

(I say Nexus, but there are others software doing the same thing, I've also heard of one named Artifactory).

Or, you could make a more complicated script which, when you build your server or client project, go download the source of your library on your "common" repository and build it.

Maven may seems a bit overkill and is (in my opinion) a pain to learn alone, but it's handy, powerful, and is the professional standard in Java and works seamlessly with Eclipse.

As for the Maven usage, the Nexus way is (depending on your scripting skill) a bit heavier to init, but more standard, easy to scale with your project, and can be used for all your other future projects.

If you're working in a professional context, I strongly advise to look for a colleague knowing it to help you mavenize your project.

Wow, that's a long question (and a complex problem). I'll try to have a go at it.

I'm not sure I understand why each user has to have a full local history when using git?

This is a central design decision with git. For the exact reasons you'd need to ask the author (Linus Torvalds), but as far as I know, the main reason is speed: Having everything local (on a fast disk or even cached in RAM) makes operations on history much faster by avoiding network access.

The biggest reason for the large repository size is that there are a lot of binary documents being inputs to tests. These files vary between .5mb and 30mb, and there are hundreds. They also have quite a lot of changes.

That is the point I would think about first. Having so many constantly changing binary files in source control seems problematic to me (even with SVN). Can't you use a different approach? Ideas:

• Unlike source code, a 3 MB binary file is probably not written by hand. If some tool/process generates it, consider integrating that into your build, instead of storing the data.

• If that is not practical, binary files are typically better off in an artifact repository (such as Artifactory for Maven & co.). Maybe that is an option for you.

I have looked at submodules, git-annex etc, but having the tests in a submodule feels wrong, as does having annex for many files for which you want full history.

Actually, this looks like git-annex would fit perfectly. git-annex basically allows you to store file contents outside a git repository (the repository contains a placeholder instead). You can store the file contents in a variety of ways (central git repo, shared drive, cloud storage...), and you can control which contents you want to have locally.

Did you maybe misunderstand how git-annex works? git-annex does store full history for all the files it manages - it just lets you choose which file contents you want to have locally.

Finally, about your questions:

What is a good best practice for using git with large repos containing many binary files that you do want history for?

In my experience, the options usually are:

• avoid the need for binaries in the repo (generate them on demand, store them elsewhere)
• use git-annex (or a similar solution, such as Git LFS)
• live with a big repo (not all git operations are affected by big files, and if you have a fast computer and drive, it can be quite workable)

Is shallow cloning usable as a normal mode of operation or is it a "hack"?

That might be doable; however, I don't think this will solve your problem:

• you'd lose of git's benefits that come from having full history, such as quick searching of the history
• merges can become tricky, because AKAIK you must have at least the history back to the branch point to merge
• users would need to re-clone periodically to keep the size of their clone small
• it's just an uncommon way of using git, so you'd likely run into problems with many tools

How big is "too big" for a git repository (on premises)? Should we avoid switching if we can get it down to 4GB? 2GB?

That depends on the structure of the repo (few/many files etc.), on what you want to do, on how beefy your computers are, and on your patience :-).

To give you a quick idea: On my (newish, but low-spec) laptop, committing a 500 MB file takes 30-60s. Just listing history (git log etc.) is not affected by big files; things like "git log -S" which must scan file content are very slow - however, the speed is mainly dominated by I/O, so it's not really git's fault.

On a 3 GB repo with a handful of revisions, "git log -S" takes about a minute.

So I'd say a couple of GB is ok, though not ideal. More than 10-20 GB is probably pushing it, but it might be doable - you'd have to try it.