diff --git a/internal/src/clippy_utils/repository.rs b/internal/src/clippy_utils/repository.rs
index c51feec84..151b573bd 100644
--- a/internal/src/clippy_utils/repository.rs
+++ b/internal/src/clippy_utils/repository.rs
@@ -1,6 +1,6 @@
-use crate::{clone, git2::Repository};
+use crate::{clone, env, git2::Repository};
 use anyhow::{Context, Result};
-use std::{cell::RefCell, rc::Rc};
+use std::{cell::RefCell, path::PathBuf, rc::Rc};
 use tempfile::{TempDir, tempdir};
 
 const RUST_CLIPPY_URL: &str = "https://github.com/rust-lang/rust-clippy";
@@ -18,7 +18,38 @@ pub fn clippy_repository(quiet: bool) -> Result<Rc<Repository>> {
 
         let tempdir = tempdir().with_context(|| "`tempdir` failed")?;
 
-        let repository = clone(RUST_CLIPPY_URL, "master", tempdir.path(), quiet).map(Rc::new)?;
+        let repository = if let Some(path) = std::env::var_os(env::DYLINT_CLIPPY_REPO) {
+            anyhow::ensure!(
+                !path.is_empty(),
+                "{} must not be empty",
+                env::DYLINT_CLIPPY_REPO
+            );
+            let path = PathBuf::from(path);
+            // EricLiu2000: Revision searches change HEAD and the worktree. Keep the supplied
+            // repository unchanged, and clone only from its local object database.
+            let source = Repository::open(&path).with_context(|| {
+                format!(
+                    "{} must point to a Git repository: `{}`",
+                    env::DYLINT_CLIPPY_REPO,
+                    path.display()
+                )
+            })?;
+            let source_path = source.path().to_str().ok_or_else(|| {
+                anyhow::anyhow!(
+                    "Clippy Git repository path is not valid UTF-8: `{}`",
+                    source.path().display()
+                )
+            })?;
+            Repository::clone(source_path, &tempdir).with_context(|| {
+                format!(
+                    "Could not clone local Clippy repository `{}`",
+                    path.display()
+                )
+            })?
+        } else {
+            clone(RUST_CLIPPY_URL, "master", tempdir.path(), quiet)?
+        };
+        let repository = Rc::new(repository);
 
         cell.replace((tempdir, repository.clone()));
 
@@ -39,3 +70,114 @@ fn parse_date(date_str: &str) -> Option<[u32; 3]> {
         .map(<[u32; 3]>::try_from)
         .and_then(Result::ok)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::CommandExt;
+    use std::{
+        fs::{create_dir, read_to_string, write},
+        path::Path,
+        process::Command,
+    };
+
+    const DYLINT_TEST_REPOSITORY: &str = "DYLINT_TEST_REPOSITORY";
+
+    #[cfg_attr(
+        dylint_lib = "general",
+        allow(
+            non_thread_safe_call_in_test,
+            reason = "All writes use a private temporary directory"
+        )
+    )]
+    #[test]
+    fn supplied_repository() {
+        if std::env::var_os(DYLINT_TEST_REPOSITORY).is_some() {
+            let repository = clippy_repository(true).unwrap();
+            let head = repository
+                .head()
+                .and_then(|reference| reference.peel_to_commit())
+                .unwrap();
+            assert_eq!("second", head.message().unwrap());
+            let parent = head.parent(0).unwrap();
+            repository.checkout_tree(parent.as_object(), None).unwrap();
+            repository.set_head_detached(parent.id()).unwrap();
+            assert_eq!(
+                "first",
+                read_to_string(repository.workdir().unwrap().join("source")).unwrap()
+            );
+            return;
+        }
+
+        let dir = tempdir().unwrap();
+        let repository = Repository::init(&dir).unwrap();
+        let signature = git2::Signature::now("Test", "test@example.com").unwrap();
+        let commit = |contents: &str, parents: &[&git2::Commit<'_>]| {
+            write(dir.path().join("source"), contents).unwrap();
+            let mut index = repository.index().unwrap();
+            index.add_path(Path::new("source")).unwrap();
+            let oid = index.write_tree().unwrap();
+            let tree = repository.find_tree(oid).unwrap();
+            repository
+                .commit(
+                    Some("HEAD"),
+                    &signature,
+                    &signature,
+                    contents,
+                    &tree,
+                    parents,
+                )
+                .unwrap()
+        };
+        let first = commit("first", &[]);
+        let second = commit("second", &[&repository.find_commit(first).unwrap()]);
+        repository.set_head_detached(second).unwrap();
+
+        run_child(dir.path(), "supplied_repository");
+    }
+
+    #[cfg_attr(
+        dylint_lib = "general",
+        allow(
+            non_thread_safe_call_in_test,
+            reason = "All writes use a private temporary directory"
+        )
+    )]
+    #[test]
+    fn invalid_supplied_repository() {
+        if std::env::var_os(DYLINT_TEST_REPOSITORY).is_some() {
+            let error = clippy_repository(true).err().unwrap();
+            assert!(format!("{error:#}").contains(env::DYLINT_CLIPPY_REPO));
+            return;
+        }
+
+        let dir = tempdir().unwrap();
+        let file = dir.path().join("file");
+        write(&file, "not a repository").unwrap();
+        let directory = dir.path().join("directory");
+        create_dir(&directory).unwrap();
+        for path in [
+            Path::new(""),
+            &dir.path().join("missing"),
+            &file,
+            &directory,
+        ] {
+            run_child(path, "invalid_supplied_repository");
+        }
+    }
+
+    // EricLiu2000: Isolate environment inputs and the thread-local repository cache for each case.
+    fn run_child(path: &Path, test: &str) {
+        Command::new(std::env::current_exe().unwrap())
+            .args([
+                "--exact",
+                &format!("clippy_utils::repository::tests::{test}"),
+                "--nocapture",
+            ])
+            .env(env::DYLINT_CLIPPY_REPO, path)
+            .env(DYLINT_TEST_REPOSITORY, "1")
+            .env(env::PATH, "")
+            .logged_output(true)
+            .unwrap();
+    }
+}
diff --git a/internal/src/env.rs b/internal/src/env.rs
index 37b037ed6..18feaf09f 100644
--- a/internal/src/env.rs
+++ b/internal/src/env.rs
@@ -21,6 +21,7 @@ declare_const!(CLIPPY_DISABLE_DOCS_LINKS);
 declare_const!(CLIPPY_DRIVER_PATH);
 declare_const!(DOCS_RS);
 declare_const!(DYLINT_BUILDING_LIBRARIES);
+declare_const!(DYLINT_CLIPPY_REPO);
 declare_const!(DYLINT_DRIVER_PATH);
 declare_const!(DYLINT_LIBRARY_PATH);
 declare_const!(DYLINT_LIBS);