Use shallow clones for submodules by jyn514 · Pull Request #89757 · rust-lang/rust (original) (raw)

using --depth=1 doesn't work, because the submodule commit referenced here may not be the latest in the submodule repo, and apparently git cannot clone at a specific commit.

Is this fixed by something?

I'm not sure what error they ran into originally, but I tested cloning rust-lang/rust from scratch and having x.py do a shallow clone for the first time, and it worked fine.

I also have some recollection that fetching new commits in a shallow repository is more work for GitHub and the client, but I could be wrong about that...

Hmm, so in CocoaPods/CocoaPods#4989 (comment) Github said shallow clones were more expensive over time if you don't subsequently use --depth=1. But we do use --depth=1 in further updates; e.g. here's a change from nightly to 1.55, which has to update most submodules:

$ git checkout 1.55
M	library/backtrace
M	library/stdarch
M	src/tools/cargo
M	src/tools/miri
M	src/tools/rls
$ x check
Updating only changed submodules
Updating submodule src/tools/cargo
Submodule path 'src/tools/cargo': checked out '32da73ab19417aa89686e1d85c1440b72fdf877d'
Updating submodule src/tools/rls
Submodule path 'src/tools/rls': checked out 'a82a0527057eab59c24a0452add35ccb39584e80'
Updating submodule src/tools/miri
Submodule path 'src/tools/miri': checked out 'e2872a3f2a26154b91a6a6085d56016509803c61'
Updating submodule library/backtrace
Submodule path 'library/backtrace': checked out '221483ebaf45df5c956adffee2d4024e7c3b96b8'
Submodule 'backtrace-sys/src/libbacktrace' (https://github.com/rust-lang/libbacktrace) registered for path 'library/backtrace/crates/backtrace-sys/src/libbacktrace'
Cloning into '/home/joshua/src/rust/rust-shallow/library/backtrace/crates/backtrace-sys/src/libbacktrace'...
remote: Enumerating objects: 363, done.        
remote: Total 363 (delta 0), reused 0 (delta 0), pack-reused 363        
Receiving objects: 100% (363/363), 846.61 KiB | 2.20 MiB/s, done.
Resolving deltas: 100% (262/262), done.
Submodule path 'library/backtrace/crates/backtrace-sys/src/libbacktrace': checked out '5c88e094a691bb803d4bba342403a10459abad9e'
Updating submodule library/stdarch
Submodule path 'library/stdarch': checked out '3001c75a1d2a81d2a76bef139c69387cb2ebb820'

So I'm not sure that problem is relevant here. (We also don't have many thousands of people running fetch every second, I would expect most contributors to only update submodules maybe once or twice a week depending how often they contribute.)