Reuse the result of which git (#8224)

## Summary

Cache the path to git executable in a `LazyLock` and reuse it throughout
the process. This might reduce some costs on finding the git executable.

Cargo.lock

@@ -4680,6 +4680,7 @@ dependencies = [
  "uv-cache-key",
  "uv-fs",
  "uv-static",
+ "which",
 ]
 
 [[package]]

crates/uv-git/Cargo.toml

@@ -32,3 +32,4 @@ thiserror = { workspace = true }
 tokio = { workspace = true }
 tracing = { workspace = true }
 url = { workspace = true }
+which = { workspace = true }

crates/uv-git/src/git.rs

@@ -4,6 +4,7 @@
 use std::fmt::Display;
 use std::path::{Path, PathBuf};
 use std::str::{self, FromStr};
+use std::sync::LazyLock;
 
 use crate::sha::GitOid;
 use crate::GitSha;
@@ -11,6 +12,7 @@ use anyhow::{anyhow, Context, Result};
 use cargo_util::{paths, ProcessBuilder};
 use reqwest::StatusCode;
 use reqwest_middleware::ClientWithMiddleware;
+
 use tracing::debug;
 use url::Url;
 use uv_fs::Simplified;
@@ -20,6 +22,9 @@ use uv_static::EnvVars;
 /// checkout is ready to go. See [`GitCheckout::reset`] for why we need this.
 const CHECKOUT_READY_LOCK: &str = ".ok";
 
+/// A global cache of the result of `which git`.
+pub static GIT: LazyLock<Result<PathBuf, which::Error>> = LazyLock::new(|| which::which("git"));
+
 /// A reference to commit or commit-ish.
 #[derive(
     Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, serde::Serialize, serde::Deserialize,
@@ -158,7 +163,7 @@ impl GitRepository {
     /// Opens an existing Git repository at `path`.
     pub(crate) fn open(path: &Path) -> Result<GitRepository> {
         // Make sure there is a Git repository at the specified path.
-        ProcessBuilder::new("git")
+        ProcessBuilder::new(GIT.as_ref()?)
             .arg("rev-parse")
             .cwd(path)
             .exec_with_output()?;
@@ -177,7 +182,7 @@ impl GitRepository {
         // opts.external_template(false);
 
         // Initialize the repository.
-        ProcessBuilder::new("git")
+        ProcessBuilder::new(GIT.as_ref()?)
             .arg("init")
             .cwd(path)
             .exec_with_output()?;
@@ -189,7 +194,7 @@ impl GitRepository {
 
     /// Parses the object ID of the given `refname`.
     fn rev_parse(&self, refname: &str) -> Result<GitOid> {
-        let result = ProcessBuilder::new("git")
+        let result = ProcessBuilder::new(GIT.as_ref()?)
             .arg("rev-parse")
             .arg(refname)
             .cwd(&self.path)
@@ -295,7 +300,7 @@ impl GitDatabase {
 
     /// Get a short OID for a `revision`, usually 7 chars or more if ambiguous.
     pub(crate) fn to_short_id(&self, revision: GitOid) -> Result<String> {
-        let output = ProcessBuilder::new("git")
+        let output = ProcessBuilder::new(GIT.as_ref()?)
             .arg("rev-parse")
             .arg("--short")
             .arg(revision.as_str())
@@ -372,7 +377,7 @@ impl GitCheckout {
         // Perform a local clone of the repository, which will attempt to use
         // hardlinks to set up the repository. This should speed up the clone operation
         // quite a bit if it works.
-        ProcessBuilder::new("git")
+        ProcessBuilder::new(GIT.as_ref()?)
             .arg("clone")
             .arg("--local")
             // Make sure to pass the local file path and not a file://... url. If given a url,
@@ -418,7 +423,7 @@ impl GitCheckout {
         debug!("reset {} to {}", self.repo.path.display(), self.revision);
 
         // Perform the hard reset.
-        ProcessBuilder::new("git")
+        ProcessBuilder::new(GIT.as_ref()?)
             .arg("reset")
             .arg("--hard")
             .arg(self.revision.as_str())
@@ -426,7 +431,7 @@ impl GitCheckout {
             .exec_with_output()?;
 
         // Update submodules (`git submodule update --recursive`).
-        ProcessBuilder::new("git")
+        ProcessBuilder::new(GIT.as_ref()?)
             .arg("submodule")
             .arg("update")
             .arg("--recursive")
@@ -592,7 +597,7 @@ fn fetch_with_cli(
     refspecs: &[String],
     tags: bool,
 ) -> Result<()> {
-    let mut cmd = ProcessBuilder::new("git");
+    let mut cmd = ProcessBuilder::new(GIT.as_ref()?);
     cmd.arg("fetch");
     if tags {
         cmd.arg("--tags");

crates/uv-git/src/lib.rs

@@ -1,7 +1,7 @@
 use url::Url;
 
 pub use crate::credentials::{store_credentials_from_url, GIT_STORE};
-pub use crate::git::GitReference;
+pub use crate::git::{GitReference, GIT};
 pub use crate::resolver::{
     GitResolver, GitResolverError, RepositoryReference, ResolvedRepositoryReference,
 };

crates/uv/src/commands/project/init.rs

@@ -11,6 +11,7 @@ use uv_cli::AuthorFrom;
 use uv_client::{BaseClientBuilder, Connectivity};
 use uv_configuration::{VersionControlError, VersionControlSystem};
 use uv_fs::{Simplified, CWD};
+use uv_git::GIT;
 use uv_pep440::Version;
 use uv_pep508::PackageName;
 use uv_python::{
@@ -896,14 +897,14 @@ fn get_author_info(path: &Path, author_from: AuthorFrom) -> Option<Author> {
 
 /// Fetch the default author from git configuration.
 fn get_author_from_git(path: &Path) -> Result<Author> {
-    let Ok(git) = which::which("git") else {
+    let Ok(git) = GIT.as_ref() else {
         anyhow::bail!("`git` not found in PATH")
     };
 
     let mut name = None;
     let mut email = None;
 
-    let output = Command::new(&git)
+    let output = Command::new(git)
         .arg("config")
         .arg("--get")
         .arg("user.name")
@@ -915,7 +916,7 @@ fn get_author_from_git(path: &Path) -> Result<Author> {
         name = Some(String::from_utf8_lossy(&output.stdout).trim().to_string());
     }
 
-    let output = Command::new(&git)
+    let output = Command::new(git)
         .arg("config")
         .arg("--get")
         .arg("user.email")

crates/uv/tests/it/pip_compile.rs

@@ -11397,6 +11397,9 @@ fn git_source_refs() -> Result<()> {
 fn git_source_missing_tag() -> Result<()> {
     let context = TestContext::new("3.12");
 
+    let mut filters = context.filters();
+    filters.push(("`.*/git fetch (.*)`", "`git fetch $1`"));
+
     let pyproject_toml = context.temp_dir.child("pyproject.toml");
     pyproject_toml.write_str(indoc! {r#"
         [project]
@@ -11410,7 +11413,7 @@ fn git_source_missing_tag() -> Result<()> {
         uv-public-pypackage = { git = "https://github.com/astral-test/uv-public-pypackage", tag = "missing" }
     "#})?;
 
-    uv_snapshot!(context.filters(), context.pip_compile()
+    uv_snapshot!(filters, context.pip_compile()
         .arg("pyproject.toml"), @r###"
     success: false
     exit_code: 2

crates/uv/tests/it/pip_install.rs

@@ -1594,7 +1594,7 @@ fn install_git_public_https_missing_branch_or_tag() {
 
     let mut filters = context.filters();
     // Windows does not style the command the same as Unix, so we must omit it from the snapshot
-    filters.push(("`git fetch .*`", "`git fetch [...]`"));
+    filters.push(("`.*/git(.exe)? fetch .*`", "`git fetch [...]`"));
     filters.push(("exit status", "exit code"));
 
     uv_snapshot!(filters, context.pip_install()
@@ -1624,7 +1624,7 @@ fn install_git_public_https_missing_commit() {
 
     let mut filters = context.filters();
     // Windows does not style the command the same as Unix, so we must omit it from the snapshot
-    filters.push(("`git fetch .*`", "`git fetch [...]`"));
+    filters.push(("`.*/git(.exe)? fetch .*`", "`git fetch [...]`"));
     filters.push(("exit status", "exit code"));
 
     // There are flakes on Windows where this irrelevant error is appended
@@ -1842,6 +1842,7 @@ fn install_git_private_https_pat_not_authorized() {
 
     let mut filters = context.filters();
     filters.insert(0, (token, "***"));
+    filters.push(("`.*/git fetch (.*)`", "`git fetch $1`"));
 
     // We provide a username otherwise (since the token is invalid), the git cli will prompt for a password
     // and hang the test