Feature/auto detect main branch

[emanb29]

Many repos I work on use dev or develop for the trunk branch -- it'd be convenient for those to be protected as defaults. However, others may well use dev as an intentionally-volatile branch. Instead of guessing, we can infer the default branch by inspecting origin/HEAD and protect it as well as the common main+master. If that fails for whatever reason, fall back to the previous default of master+main

Note that this does deviate from the behavior of pre-commit, so if cross-compatibility is a critical, this may not be acceptable.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.15%. Comparing base (143bfe1) to head (ab58911).
⚠️ Report is 12 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1898   +/-   ##
=======================================
  Coverage   92.15%   92.15%           
=======================================
  Files         112      112           
  Lines       22529    22622   +93     
=======================================
+ Hits        20761    20847   +86     
- Misses       1768     1775    +7     

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[prek-ci-bot]

📦 Cargo Bloat Comparison

Binary size change: -0.39% (25.6 MiB → 25.5 MiB)

Expand for cargo-bloat output

Head Branch Results

 File  .text     Size             Crate Name
 1.3%   2.6% 332.0KiB        aws_lc_sys aws_lc_0_39_0_aes_gcm_encrypt_avx512
 1.3%   2.6% 332.0KiB        aws_lc_sys aws_lc_0_39_0_aes_gcm_decrypt_avx512
 0.3%   0.7%  86.6KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.6%  80.7KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.5%  68.3KiB             prek? <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
 0.2%   0.4%  57.0KiB              prek prek::languages::<impl prek::config::Language>::install::{{closure}}
 0.2%   0.4%  51.0KiB annotate_snippets annotate_snippets::renderer::render::render
 0.2%   0.4%  47.5KiB              prek prek::run::{{closure}}
 0.2%   0.3%  42.0KiB              prek prek::cli::run::run::run::{{closure}}
 0.1%   0.3%  32.4KiB             prek? <prek::cli::RunArgs as clap_builder::derive::Args>::augment_args
 0.1%   0.3%  31.7KiB             prek? <prek::config::_::<impl serde_core::de::Deserialize for prek::config::Config>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map
 0.1%   0.2%  28.0KiB      serde_saphyr saphyr_parser_bw::scanner::Scanner<T>::fetch_more_tokens
 0.1%   0.2%  28.0KiB        aws_lc_sys aws_lc_0_39_0_edwards25519_scalarmuldouble_alt
 0.1%   0.2%  27.5KiB        aws_lc_sys aws_lc_0_39_0_edwards25519_scalarmuldouble
 0.1%   0.2%  26.7KiB              prek prek::cli::try_repo::try_repo::{{closure}}
 0.1%   0.2%  26.6KiB               std core::ptr::drop_in_place<prek::languages::<impl prek::config::Language>::install::{{closure}}>
 0.1%   0.2%  22.8KiB              prek prek::hooks::meta_hooks::MetaHooks::run::{{closure}}
 0.1%   0.2%  22.6KiB      serde_saphyr saphyr_parser_bw::scanner::Scanner<T>::fetch_more_tokens
 0.1%   0.2%  22.3KiB         [Unknown] Lp384_montjscalarmul_alt_p384_montjadd
 0.1%   0.2%  21.6KiB     serde_saphyr? <serde_saphyr::de::YamlDeserializer as serde_core::de::Deserializer>::deserialize_map
41.8%  86.2%  10.7MiB                   And 23871 smaller methods. Use -n N to show more.
48.4% 100.0%  12.4MiB                   .text section size, the file size is 25.5MiB

Base Branch Results

 File  .text     Size             Crate Name
 1.3%   2.6% 332.0KiB        aws_lc_sys aws_lc_0_39_0_aes_gcm_encrypt_avx512
 1.3%   2.6% 332.0KiB        aws_lc_sys aws_lc_0_39_0_aes_gcm_decrypt_avx512
 0.3%   0.7%  86.6KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.6%  80.7KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.5%  69.2KiB             prek? <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
 0.2%   0.4%  57.0KiB              prek prek::languages::<impl prek::config::Language>::install::{{closure}}
 0.2%   0.4%  51.0KiB annotate_snippets annotate_snippets::renderer::render::render
 0.2%   0.4%  47.5KiB              prek prek::run::{{closure}}
 0.2%   0.3%  42.0KiB              prek prek::cli::run::run::run::{{closure}}
 0.1%   0.3%  33.3KiB             prek? <prek::cli::RunArgs as clap_builder::derive::Args>::augment_args
 0.1%   0.2%  31.7KiB             prek? <prek::config::_::<impl serde_core::de::Deserialize for prek::config::Config>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map
 0.1%   0.2%  28.0KiB      serde_saphyr saphyr_parser_bw::scanner::Scanner<T>::fetch_more_tokens
 0.1%   0.2%  28.0KiB        aws_lc_sys aws_lc_0_39_0_edwards25519_scalarmuldouble_alt
 0.1%   0.2%  27.5KiB        aws_lc_sys aws_lc_0_39_0_edwards25519_scalarmuldouble
 0.1%   0.2%  26.7KiB              prek prek::cli::try_repo::try_repo::{{closure}}
 0.1%   0.2%  26.6KiB               std core::ptr::drop_in_place<prek::languages::<impl prek::config::Language>::install::{{closure}}>
 0.1%   0.2%  22.8KiB              prek prek::hooks::meta_hooks::MetaHooks::run::{{closure}}
 0.1%   0.2%  22.6KiB      serde_saphyr saphyr_parser_bw::scanner::Scanner<T>::fetch_more_tokens
 0.1%   0.2%  22.3KiB         [Unknown] Lp384_montjscalarmul_alt_p384_montjadd
 0.1%   0.2%  21.6KiB     serde_saphyr? <serde_saphyr::de::YamlDeserializer as serde_core::de::Deserializer>::deserialize_map
41.7%  86.2%  10.7MiB                   And 24017 smaller methods. Use -n N to show more.
48.4% 100.0%  12.4MiB                   .text section size, the file size is 25.6MiB

[prek-ci-bot]

⚡️ Hyperfine Benchmarks

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

Environment

• OS: Linux 6.17.0-1008-azure
• CPU: 4 cores
• prek version: prek 0.3.8+25 (993dbec 2026-04-05)
• Rust version: rustc 1.94.1 (e408947bf 2026-03-25)
• 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	2.1 ± 0.1	2.0	2.4	1.00 ± 0.04
prek-head --version	2.1 ± 0.1	2.1	2.3	1.00

prek list

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base list	8.5 ± 0.2	8.1	9.8	1.01 ± 0.04
prek-head list	8.4 ± 0.2	8.1	9.0	1.00

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

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base validate-config .pre-commit-config.yaml	2.9 ± 0.1	2.7	3.0	1.00
prek-head validate-config .pre-commit-config.yaml	3.1 ± 1.9	2.7	16.5	1.09 ± 0.67

prek sample-config

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base sample-config	2.4 ± 0.4	2.3	5.0	1.00 ± 0.20
prek-head sample-config	2.4 ± 0.3	2.3	4.6	1.00

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	138.6 ± 5.0	132.3	147.0	1.00
prek-head run --all-files	140.0 ± 2.8	133.9	143.1	1.01 ± 0.04

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

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --all-files	140.0 ± 4.6	132.6	148.7	1.00
prek-head run --all-files	142.1 ± 3.3	135.7	148.3	1.02 ± 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	140.4 ± 3.3	132.2	147.2	1.01 ± 0.04
prek-head run --all-files	138.9 ± 4.0	132.7	148.6	1.00

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	20.1 ± 1.4	18.9	26.7	1.03 ± 0.08
prek-head run trailing-whitespace --all-files	19.5 ± 0.6	18.5	21.0	1.00

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	37.7 ± 44.7	22.9	254.4	1.44 ± 1.71
prek-head run end-of-file-fixer --all-files	26.2 ± 2.4	22.9	30.1	1.00

prek run check-json --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-json --all-files	11.0 ± 0.4	10.5	12.5	1.01 ± 0.05
prek-head run check-json --all-files	10.9 ± 0.4	10.4	11.7	1.00

prek run check-yaml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-yaml --all-files	11.2 ± 0.8	10.4	13.1	1.05 ± 0.08
prek-head run check-yaml --all-files	10.7 ± 0.2	10.4	11.1	1.00

prek run check-toml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-toml --all-files	11.0 ± 0.4	10.4	12.1	1.01 ± 0.05
prek-head run check-toml --all-files	10.9 ± 0.4	10.3	11.7	1.00

prek run check-xml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-xml --all-files	10.9 ± 0.3	10.4	11.7	1.00
prek-head run check-xml --all-files	10.9 ± 0.3	10.2	11.5	1.00 ± 0.04

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

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run detect-private-key --all-files	16.6 ± 1.0	15.0	18.5	1.00
prek-head run detect-private-key --all-files	16.9 ± 1.3	14.7	19.4	1.02 ± 0.10

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	21.9 ± 1.5	19.0	24.3	1.02 ± 0.11
prek-head run fix-byte-order-marker --all-files	21.5 ± 1.8	18.8	24.2	1.00

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	4.3 ± 0.1	4.2	4.5	1.00
prek-head install-hooks	4.4 ± 0.1	4.2	4.6	1.01 ± 0.04

prek install-hooks (warm - with cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base install-hooks	4.2 ± 0.0	4.2	4.3	1.00
prek-head install-hooks	4.2 ± 0.0	4.2	4.3	1.00 ± 0.01

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	48.9 ± 0.9	47.4	51.0	1.01 ± 0.03
prek-head run	48.6 ± 1.3	46.1	51.6	1.00

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

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --files '*.json'	8.2 ± 0.2	7.8	8.6	1.01 ± 0.04
prek-head run --files '*.json'	8.0 ± 0.2	7.9	8.5	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	12.3 ± 0.3	11.8	12.8	1.00
prek-head run --dry-run --all-files	12.3 ± 0.3	12.1	13.1	1.00 ± 0.03

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	11.3 ± 0.1	11.0	11.6	1.00
prek-head run check-hooks-apply --all-files	11.4 ± 0.3	11.1	12.4	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	11.2 ± 0.1	11.0	11.4	1.00
prek-head run check-useless-excludes --all-files	11.4 ± 0.5	11.1	13.1	1.02 ± 0.04

prek run identity --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run identity --all-files	9.8 ± 0.2	9.6	10.2	1.00
prek-head run identity --all-files	9.8 ± 0.1	9.7	10.0	1.00 ± 0.02

[Copilot]

Pull request overview

Adds repo-aware default-branch protection to the no-commit-to-branch builtin hook by attempting to infer the default branch from origin/HEAD, extending the existing main/master defaults.

Changes:

• Detects the default branch via git symbolic-ref --short origin/HEAD and includes it in the hook’s default protected branch list.
• Updates builtin hook documentation to describe the expanded defaults.
• Adds unit tests for argument parsing and branch/pattern matching behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
docs/builtin.md	Updates no-commit-to-branch docs to mention origin/HEAD-based default branch protection.
crates/prek/src/hooks/pre_commit_hooks/no_commit_to_branch.rs	Implements origin/HEAD detection to extend default protected branches and adds unit tests.

[Copilot]

DEFAULT_BRANCHES is a process-global LazyLock that detects the default branch using the current working directory once and then reuses it forever. In a prek run that executes hooks for multiple projects/repos in the same process, this can cause the “detected” branch from the first repo to be applied to subsequent repos (wrong branches protected). Compute the detected default branch per hook invocation (scoped to hook.work_dir() / repo path) instead of caching it in a static.

[emanb29]

Silly question, but -- is such a prek run possible? I thought one run was always one project/repo.

[Copilot]

Using default_values_t = DEFAULT_BRANCHES.clone() means argument parsing will force initialization of DEFAULT_BRANCHES (spawning a git symbolic-ref origin/HEAD subprocess) even when the user provides explicit -b/--branch values. Consider parsing branches without defaults (or as Option<Vec<String>>) and applying the computed defaults only when the argument is absent, inside no_commit_to_branch where you can also run the git command with .current_dir(hook.work_dir()) and reuse existing git/process helpers.

[emanb29]

Ooh, yeah this is a bit gross. I wanted to stick with the arg-parsing pattern, but avoiding the unnecessary git call may be worth switching to a runtime git call (that may also allow switching to an async shell-out to git instead of the current blocking approach)