When to use git subtree?

Question

What problem does git subtree solve? When and why should I use that feature?

I\'ve read that it is used for repository separation. But why would I not j

Answer 1

First of: I believe your question tends to get strongly opinionated answers and may be considered off-topic here. However I don't like that SO policy and would push the border of being on-topic a bit outward, so I like to answer instead and hope others do as well.

On the GitHub tutorial that you pointed to there's a link to How to use the subtree merge strategy which gives a viewpoint on advantages/disadvantages:

Comparing subtree merge with submodules

The benefit of using subtree merge is that it requires less administrative burden from the users of your repository. It works with older (before Git v1.5.2) clients and you have the code right after clone.

However if you use submodules then you can choose not to transfer the submodule objects. This may be a problem with the subtree merge.

Also, in case you make changes to the other project, it is easier to submit changes if you just use submodules.

Here's my viewpoint based on the above:

I often work with folks (=committers) who are no regular git users, some still (and will forever) struggle with version control. Educating them about how to use the submodule merge strategy is basically impossible. It involves the concepts of additional remotes, about merging, branches, and then mixing it all into one workflow. Pulling from upstream and pushing upstream is a two stage process. Since branches is difficult to understand for them, this is all hopeless.

With submodules it's still too complicated for them (sigh) but it is easier to understand: It's just a repo within a repo (they are familiar with hierarchy) and you can do your pushing and pulling as usual.

Providing simple wrapper scripts is easier imho for the submodule workflow.

For large super-repos with many sub-repos the point of choosing not to clone data of some sub-repos is an important advantage of the submodules. We can limit this based on work requirements and disk space usage.

Access control might be different. Haven't had this issue yet, but if different repos require different access controls, effectively banning some users from some sub-repos, I wonder if that's easier to accomplish with the submodule approach.

Personally I'm undecided what to use myself. So I share your confusion :o]