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Kha
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Oct 17, 2021
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| runProgram("git", true, { "--git-dir", repoDir, "--work-tree", tmpDir, "checkout", "--quiet", input.getRev()->gitRev(), "." }); | ||
| // `-C` should be redundant, probably a bug in `git submodule` | ||
| runProgram("git", true, { "--git-dir", repoDir, "--work-tree", tmpDir, "-C", tmpDir, "submodule", "--quiet", "update", "--init", "--recursive" }); |
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This sequence (which existed before) should probably be covered by a repo lock to prevent races
This was referenced Oct 20, 2021
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... siphoning submodules stakeholders to #5497 |
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I marked this as stale due to inactivity. → More info |
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Closing in favor of #6530, see also #7862 (comment) |
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Replace the current naive submodule fetching code with one that mostly does the minimal amount of necessary work/fetching
.cache/nixas usual, thencheckout&submodule updateinto the temp directory using--work-tree. It doesn't get much more direct than that.HEADof that repo (and there is no direct way to check out submodules for a specific commit that is notHEAD). Instead, we do a cheap clone into the temp dir that shares all objects, including those of submodules, with the original repo. Note that if the submodule commit has not yet been fetched into the original repo,submodule updatewill then fetch it into the temp dir, so checking out another commit afterwards will fetch the upstream again. This could potentially be improved by fetching into.cache/nixeven for local repos.Some measurements:
Store-copying (prefetched) Nixpkgs without submodules/with submodules (old)/with submodules (new)
Store-copying a repositories with actual submodules:
And the local repo that triggered #5280 in the first place:
TL;DR: no overhead from
submodules = true;without submodules and reasonable one with submodulesI am only 90% sure this all makes sense and covers at least as many cases as the current code, so please do give it a try & come up with weird edge cases.