[llvm-dev] [RFC] One or many git repositories?

[Renato Golin via llvm-dev]

On 21 July 2016 at 01:39, Justin Lebar <jlebar at google.com> wrote:
> This is true if you s/checkout/clone/.  With a single repo, you must
> clone (download) everything (*), but after you've done so you can use
> sparse checkouts to check out (create a working copy of) only llvm and
> clang.  So you should only notice the fact that there exist things
> other than llvm and clang when you first clone (download) llvm.

So, we use that to a certain extent.

Linaro's GCC validation uses the full checkout, then do a shallow
checkout that only has the updates.

Our LLVM scripts, OTOH, clone all repos and use worktree for *all*
branches, and we only branch on the repos that we choose, for each
"working dir".

Our scripts probably would need certain modifications... but it should be fine.

But I'm not, by far, the most problematic user.

The real problem, and why people accepted sub-modules, is that a lot
of downstream people only use one or another projects. Mostly LLVM or
Clang or libc++.

Checking out all of it is bad, but having them officially interlinked,
it seems, is worse. IIUC, the problem is that the projects are now
built independently on their projects, but more and more CMake changes
are creeping in, making it harder and harder to separate their
projects from the rest of LLVM. This means they'll now depend on a
much larger body of sources that will need to be compiled together,
and will probably mean they'll abandon LLVM in favour of something
lighter.

I honestly don't know how big is that problem, I don't have it myself,
but I "can imagine" compiling LLVM and Clang without need would be
pretty bad.

cheers,
--renato