Scan check-merge-conflict files in fixed-size blocks

[j178]

Skip per-line checks in blocks without conflict markers and avoid buffering entire lines. On macOS arm64, a 128 MiB single-line input reduces peak process RSS from 142 MiB to 12 MiB.

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-28T03:05:01.189723Z	da62a64	PR opened

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[codecov]

Codecov Report

❌ Patch coverage is 98.27586% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 94.27%. Comparing base (aeea7a5) to head (da62a64).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
...src/hooks/pre_commit_hooks/check_merge_conflict.rs	98.27%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2781      +/-   ##
==========================================
+ Coverage   93.98%   94.27%   +0.28%     
==========================================
  Files         142      142              
  Lines       30388    30716     +328     
==========================================
+ Hits        28560    28957     +397     
+ Misses       1828     1759      -69     

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[prek-ci-bot]

📦 Cargo Bloat Comparison

.text size change: +0.00% (12.9 MiB → 12.9 MiB)

Expand for cargo-bloat output

Head Branch Results

File  .text     Size             Crate Name
0.1%   2.5% 332.0KiB        aws_lc_sys aws_lc_0_45_0_aes_gcm_encrypt_avx512
0.1%   2.5% 332.0KiB        aws_lc_sys aws_lc_0_45_0_aes_gcm_decrypt_avx512
0.0%   0.7%  96.5KiB              prek <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
0.0%   0.4%  49.8KiB              prek <<prek::config::hook::HookWire as serde_core::de::Deserialize>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map::<&mut <serde_saphyr::de::deserializer::YamlDeserializer as serde_core::de::Deserializer>::deserialize_map::MA>
0.0%   0.4%  48.7KiB annotate_snippets annotate_snippets::renderer::render::render
0.0%   0.4%  46.7KiB              prek <<prek::config::Config as serde_core::de::Deserialize>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map::<&mut <serde_saphyr::de::deserializer::YamlDeserializer as serde_core::de::Deserializer>::deserialize_map::MA>
0.0%   0.3%  41.8KiB              prek <prek::cli::RunOptions as clap_builder::derive::Args>::augment_args
0.0%   0.3%  39.0KiB              prek prek::cli::run::run::run::{closure#0}
0.0%   0.3%  37.4KiB              prek prek::run::{closure#0}
0.0%   0.2%  31.9KiB              prek <prek::languages::rust::rust::Rust as prek::languages::LanguageBackend>::install::{closure#0}
0.0%   0.2%  29.4KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  29.1KiB      serde_saphyr <granit_parser::scanner::Scanner<granit_parser::input::str::StrInput>>::fetch_more_tokens
0.0%   0.2%  28.6KiB              toml <toml::de::deserializer::value::ValueDeserializer as serde_core::de::Deserializer>::deserialize_any::<<prek::config::hook::HookWire as serde_core::de::Deserialize>::deserialize::__Visitor>
0.0%   0.2%  28.0KiB        aws_lc_sys aws_lc_0_45_0_edwards25519_scalarmuldouble_alt
0.0%   0.2%  27.5KiB        aws_lc_sys aws_lc_0_45_0_edwards25519_scalarmuldouble
0.0%   0.2%  27.1KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
4.1%  87.0%  11.2MiB                   And 20578 smaller methods. Use -n N to show more.
4.7% 100.0%  12.9MiB                   .text section size, the file size is 272.9MiB

Base Branch Results

File  .text     Size             Crate Name
0.1%   2.5% 332.0KiB        aws_lc_sys aws_lc_0_45_0_aes_gcm_encrypt_avx512
0.1%   2.5% 332.0KiB        aws_lc_sys aws_lc_0_45_0_aes_gcm_decrypt_avx512
0.0%   0.7%  96.5KiB              prek <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
0.0%   0.4%  49.8KiB              prek <<prek::config::hook::HookWire as serde_core::de::Deserialize>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map::<&mut <serde_saphyr::de::deserializer::YamlDeserializer as serde_core::de::Deserializer>::deserialize_map::MA>
0.0%   0.4%  48.7KiB annotate_snippets annotate_snippets::renderer::render::render
0.0%   0.4%  46.7KiB              prek <<prek::config::Config as serde_core::de::Deserialize>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map::<&mut <serde_saphyr::de::deserializer::YamlDeserializer as serde_core::de::Deserializer>::deserialize_map::MA>
0.0%   0.3%  41.3KiB              prek <prek::cli::RunOptions as clap_builder::derive::Args>::augment_args
0.0%   0.3%  39.0KiB              prek prek::cli::run::run::run::{closure#0}
0.0%   0.3%  37.4KiB              prek prek::run::{closure#0}
0.0%   0.2%  31.0KiB              prek <prek::languages::rust::rust::Rust as prek::languages::LanguageBackend>::install::{closure#0}
0.0%   0.2%  29.1KiB      serde_saphyr <granit_parser::scanner::Scanner<granit_parser::input::str::StrInput>>::fetch_more_tokens
0.0%   0.2%  28.0KiB              toml <toml::de::deserializer::value::ValueDeserializer as serde_core::de::Deserializer>::deserialize_any::<<prek::config::hook::HookWire as serde_core::de::Deserialize>::deserialize::__Visitor>
0.0%   0.2%  28.0KiB        aws_lc_sys aws_lc_0_45_0_edwards25519_scalarmuldouble_alt
0.0%   0.2%  27.6KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.5KiB        aws_lc_sys aws_lc_0_45_0_edwards25519_scalarmuldouble
0.0%   0.2%  27.1KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
4.1%  87.1%  11.2MiB                   And 20649 smaller methods. Use -n N to show more.
4.7% 100.0%  12.9MiB                   .text section size, the file size is 273.3MiB

[prek-ci-bot]

⚡️ Hyperfine Benchmarks

Summary: 0 regressions, 0 improvements above the 10% threshold.

Environment

• OS: Linux 6.17.0-1022-azure
• CPU: 4 cores
• prek version: prek 0.5.3+53 (fe6d23d 2026-09-28)
• Rust version: rustc 1.98.1 (48a229cea 2026-09-01)
• Hyperfine version: hyperfine 1.20.0

CLI Commands

Benchmarking basic commands in the main repo:

prek --version

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base --version	2.2 ± 0.2	2.1	3.6	1.00 ± 0.10
prek-head --version	2.2 ± 0.1	2.1	2.7	1.00

prek list

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base list	9.2 ± 0.1	9.0	9.9	1.01 ± 0.03
prek-head list	9.2 ± 0.3	8.9	11.0	1.00

prek validate-config .pre-commit-config.yaml

⏭️ Skipped: .pre-commit-config.yaml not found

prek sample-config

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base sample-config	2.6 ± 0.2	2.5	3.6	1.00
prek-head sample-config	2.6 ± 0.3	2.5	4.2	1.01 ± 0.13

Cold vs Warm Runs

Comparing first run (cold) vs subsequent runs (warm cache):

prek run --all-files (cold - no cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --all-files	19.6 ± 0.8	18.8	21.6	1.02 ± 0.04
prek-head run --all-files	19.3 ± 0.3	18.8	19.7	1.00

prek run --all-files (warm - with cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --all-files	19.7 ± 0.5	19.1	20.9	1.00
prek-head run --all-files	19.8 ± 0.7	19.1	22.0	1.01 ± 0.04

Full Hook Suite

Running the builtin hook suite on the benchmark workspace:

prek run --all-files (full builtin hook suite)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --all-files	19.5 ± 0.6	18.8	22.7	1.00
prek-head run --all-files	19.6 ± 0.5	18.4	21.0	1.00 ± 0.04

Individual Hook Performance

Benchmarking each hook individually on the test repo:

prek run trailing-whitespace --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run trailing-whitespace --all-files	8.5 ± 0.2	8.3	9.4	1.00
prek-head run trailing-whitespace --all-files	8.6 ± 0.3	8.2	9.7	1.00 ± 0.05

prek run end-of-file-fixer --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run end-of-file-fixer --all-files	7.8 ± 0.2	7.5	8.8	1.00
prek-head run end-of-file-fixer --all-files	7.9 ± 0.5	7.5	9.5	1.02 ± 0.07

prek run check-json --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-json --all-files	6.7 ± 0.1	6.5	7.0	1.00
prek-head run check-json --all-files	6.9 ± 0.5	6.6	9.4	1.02 ± 0.08

prek run check-yaml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-yaml --all-files	7.1 ± 0.2	6.9	7.6	1.02 ± 0.03
prek-head run check-yaml --all-files	6.9 ± 0.1	6.8	7.1	1.00

prek run check-toml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-toml --all-files	6.8 ± 0.1	6.6	7.0	1.01 ± 0.04
prek-head run check-toml --all-files	6.8 ± 0.2	6.5	7.8	1.00

prek run check-xml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-xml --all-files	7.5 ± 0.3	7.2	8.4	1.00
prek-head run check-xml --all-files	7.6 ± 0.8	7.1	11.9	1.02 ± 0.12

prek run detect-private-key --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run detect-private-key --all-files	7.3 ± 0.3	7.2	8.7	1.00
prek-head run detect-private-key --all-files	7.4 ± 0.6	7.1	10.3	1.00 ± 0.09

prek run fix-byte-order-marker --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run fix-byte-order-marker --all-files	7.3 ± 0.1	7.1	7.6	1.00
prek-head run fix-byte-order-marker --all-files	7.4 ± 0.7	7.1	11.0	1.01 ± 0.10

Installation Performance

Benchmarking hook installation (fast path hooks skip Python setup):

prek install-hooks (cold - no cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base install-hooks	4.9 ± 0.7	4.5	6.2	1.07 ± 0.16
prek-head install-hooks	4.6 ± 0.1	4.5	4.7	1.00

prek install-hooks (warm - with cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base install-hooks	4.6 ± 0.1	4.5	4.6	1.00
prek-head install-hooks	4.6 ± 0.1	4.5	4.7	1.00 ± 0.02

File Filtering/Scoping Performance

Testing different file selection modes:

prek run (staged files only)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run	20.7 ± 2.0	19.4	27.0	1.04 ± 0.10
prek-head run	19.8 ± 0.4	19.4	20.9	1.00

prek run --files '*.json' (specific file type)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --files '*.json'	5.4 ± 1.2	5.0	10.7	1.03 ± 0.25
prek-head run --files '*.json'	5.3 ± 0.4	5.0	6.9	1.00

Workspace Discovery & Initialization

Benchmarking hook discovery and initialization overhead:

prek run --dry-run --all-files (measures init overhead)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --dry-run --all-files	6.9 ± 0.2	6.8	7.7	1.00
prek-head run --dry-run --all-files	7.0 ± 0.2	6.7	7.4	1.01 ± 0.04

Meta Hooks Performance

Benchmarking meta hooks separately:

prek run check-hooks-apply --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-hooks-apply --all-files	8.1 ± 0.1	8.0	8.5	1.00
prek-head run check-hooks-apply --all-files	8.2 ± 0.2	8.0	8.7	1.01 ± 0.03

prek run check-useless-excludes --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-useless-excludes --all-files	8.4 ± 0.1	8.3	8.7	1.04 ± 0.02
prek-head run check-useless-excludes --all-files	8.1 ± 0.1	8.0	8.4	1.00

prek run identity --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run identity --all-files	7.1 ± 0.1	6.9	7.3	1.01 ± 0.02
prek-head run identity --all-files	7.0 ± 0.1	6.8	7.3	1.00