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ci: fetch git-pinned crates shallowly in the splice - #4019
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crate_universe clones every git dependency's full history into an empty CARGO_HOME on each splice; asupersync alone is about 1 GB. Cargo's shallow-deps fetch takes only the pinned commits. The splice runs the stable host cargo, so RUSTC_BOOTSTRAP lets it read the unstable option. Cold `bazel build --config=ci //:rustfmt_check` locally: 417 s and 364 s before, 75 s and 76 s after. The generated @c hub is byte-identical. With the fetch cheap again, restore the 15-minute Repository gates limit that #4017 raised to 30.
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ScriptedAlchemy
enabled auto-merge
October 15, 2026 10:29
The shallow fetch should bring the splice well under 15 minutes, but no CI run has confirmed it yet. Keep #4017's limit until one does.
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Why
Since #3983 pinned asupersync to a git rev, every CI job's crate_universe splice clones the full history of each git dependency into an empty
CARGO_HOME. asupersync alone is about 1 GB, and the clone ran past 7 minutes on a hosted runner. #4017 raised the Repository gates limit to 30 minutes as a stopgap.Cargo's
shallow-depsgit option fetches only the pinned commit of each git dependency. The splice runs rules_rust's stable host cargo (1.98.0), which ignores unstable options unlessRUSTC_BOOTSTRAP=1is set, so.bazelrcsets both through--repo_env. The mechanism covers every git dependency, so it stays in place after asupersync 0.6.0 reaches crates.io.Scope
.bazelrc: add--repo_env=CARGO_UNSTABLE_GIT=shallow-depsand--repo_env=RUSTC_BOOTSTRAP=1next to the existingCARGO_NET_GIT_FETCH_WITH_CLI..github/workflows/ci.yml: revert ci: give Repository gates room for the git crate fetch #4017. Repository gates goes back totimeout-minutes: 15.Tradeoffs
rust_host_tools.host_tools(version = "nightly/2026-09-27")pluscrate.from_cargo(host_tools = ...)) also works withoutRUSTC_BOOTSTRAP. It downloads a second 418 MB toolchain on every job, because a nightly without pinned checksums never hits the repository cache. Cold build 108 s against 75 s.CARGO_BAZEL_ISOLATED=falseand a sharedCARGO_HOME, and still restores 1.3 GB of history. The shallow fetch is 76 MB.--filter=blob:nonehas no git config that applies to cargo's URL fetches, and cargo checks out with libgit2, which cannot read a partial clone.Blast Radius
The variables reach repository rules and module extensions only, not build actions. The generated
@chub is byte-identical before and after. If the 15-minute limit proves too tight, Repository gates times out and blocks merges until the limit goes back up.Verification
Cold
bazel build --config=ci //:rustfmt_check(expunged output base, noMODULE.bazel.lock): 417 s → 75 s. The splice: 389 s → 62 s. Git databases: 1.3 GB → 76 MB.