git_filter_tree/

lib.rs

//! Filter Git tree objects by glob patterns or gitattributes.
//!
//! This crate exposes the [`FilterTree`] trait, implemented on
//! [`git2::Repository`], which produces a new tree containing only the entries
//! that match either a set of **glob patterns** or a set of **gitattributes**.
//! Trees are walked recursively; patterns are matched against full paths from
//! the tree root.
//!
//! It is the plumbing library behind the `git filter-tree` command and the
//! [`git-rewrite`](https://docs.rs/git-rewrite) porcelain.
//!
//! # Filter by Pattern
//!
//! ```no_run
//! use git_filter_tree::FilterTree as _;
//!
//! let repo = git2::Repository::open_from_env()?;
//! let tree = repo.head()?.peel_to_tree()?;
//!
//! // Produce a new tree that contains only Rust source files.
//! let filtered = repo.filter_by_patterns(&tree, &["**/*.rs"])?;
//! println!("tree sha: {}", filtered.id());
//! # Ok::<(), Box<dyn std::error::Error>>(())
//! ```
//!
//! A trailing `/` is expanded to `dir/**`, so `"src/"` keeps all files under
//! `src/`. Multiple patterns are OR-ed together.
//!
//! # Filter by Attributes
//!
//! ```no_run
//! use git_filter_tree::FilterTree as _;
//!
//! let repo = git2::Repository::open_from_env()?;
//! let tree = repo.head()?.peel_to_tree()?;
//!
//! // Keep only entries that have the `export` attribute set in .gitattributes.
//! let filtered = repo.filter_by_attributes(&tree, &["export"])?;
//! println!("tree sha: {}", filtered.id());
//! # Ok::<(), Box<dyn std::error::Error>>(())
//! ```
//!
//! All listed attributes must be set (AND semantics). Entries with an
//! attribute explicitly unset (`-export`) or unspecified are excluded.
pub mod exe;
use std::path::{Path, PathBuf};

pub use git2::{Error, Repository};
use globset::GlobSetBuilder;

pub trait FilterTree {
    /// Filters tree entries by gitattributes-style patterns and returns a new tree with contents
    /// filtered through the provided patterns. Recursively walks the tree and matches patterns
    /// against full paths from the tree root.
    ///
    /// The `patterns` type is an array of string slices and not a glob type because Git has
    /// specific glob syntax that differs from standard shell syntax.
    fn filter_by_patterns<'a>(
        &'a self,
        tree: &'a git2::Tree<'a>,
        patterns: &[&str], // TODO create a `git-glob` crate to handle patterns more gracefully
    ) -> Result<git2::Tree<'a>, Error>;

    /// Filters tree entries by gitattributes and returns a new tree with contents filtered.
    /// Recursively walks the tree and matches attributes against full paths from the tree root.
    ///
    /// The `attributes` type is an array of string slices. For attributes which haves values,
    /// not simply set or unset, use typical `.gitattributes` syntax.
    fn filter_by_attributes<'a>(
        &'a self,
        tree: &'a git2::Tree<'a>,
        attributes: &[&str],
    ) -> Result<git2::Tree<'a>, Error>;
}

impl FilterTree for git2::Repository {
    fn filter_by_patterns<'a>(
        &'a self,
        tree: &'a git2::Tree<'a>,
        patterns: &[&str],
    ) -> Result<git2::Tree<'a>, Error> {
        if patterns.is_empty() {
            return Err(Error::from_str("At least one pattern is required"));
        }

        // Build GlobSet matcher
        let mut glob_builder = GlobSetBuilder::new();
        for pattern in patterns {
            // A trailing `/` means "this directory" in gitattributes/gitignore
            // semantics.  Normalize to `dir/**` so globset matches all files
            // under the directory recursively.
            let normalized: String;
            let pat = if pattern.ends_with('/') {
                normalized = format!("{}**", pattern);
                normalized.as_str()
            } else {
                pattern
            };
            let glob = globset::Glob::new(pat)
                .map_err(|e| Error::from_str(&format!("Invalid pattern '{}': {}", pattern, e)))?;
            glob_builder.add(glob);
        }

        let matcher = glob_builder
            .build()
            .map_err(|e| Error::from_str(&e.to_string()))?;

        // Recursively filter the tree
        filter_tree_recursive(self, tree, None, &|_repo, path| matcher.is_match(path))
    }

    fn filter_by_attributes<'a>(
        &'a self,
        tree: &'a git2::Tree<'a>,
        attributes: &[&str],
    ) -> Result<git2::Tree<'a>, Error> {
        if attributes.is_empty() {
            return Err(git2::Error::from_str("at least one attribute is required"));
        }

        filter_tree_recursive(self, tree, None, &|repo, path| {
            for attribute in attributes {
                match repo.get_attr(path, attribute, git2::AttrCheckFlags::FILE_THEN_INDEX) {
                    Ok(Some(value)) => {
                        let value = git2::AttrValue::from_string(Some(value));
                        match value {
                            git2::AttrValue::Unspecified => return false,
                            git2::AttrValue::False => return false,
                            _ => {}
                        }
                    }
                    Ok(None) => return false,
                    Err(_) => return false,
                }
            }

            true
        })
    }
}

/// Recursively filters a tree, matching patterns against full paths.
/// Returns a new tree containing only entries that match or have matching descendants.
fn filter_tree_recursive<'a, F>(
    repo: &'a Repository,
    tree: &'a git2::Tree<'a>,
    prefix: Option<&Path>,
    predicate: &F,
) -> Result<git2::Tree<'a>, Error>
where
    F: Fn(&Repository, &Path) -> bool,
{
    let mut builder = repo.treebuilder(None)?;

    for entry in tree.iter() {
        let Some(name) = entry.name() else {
            return Err(Error::from_str("name has invalid UTF-8"));
        };

        let full_path = match prefix {
            Some(subdir) => subdir.join(name),
            None => PathBuf::from(name.to_string()),
        };

        match entry.kind() {
            Some(git2::ObjectType::Blob) => {
                if predicate(repo, &full_path) {
                    builder.insert(name, entry.id(), entry.filemode())?;
                }
            }
            Some(git2::ObjectType::Tree) => {
                let subtree = entry.to_object(repo)?.peel_to_tree()?;
                let filtered_subtree =
                    filter_tree_recursive(repo, &subtree, Some(&full_path), predicate)?;
                if !filtered_subtree.is_empty() {
                    builder.insert(name, filtered_subtree.id(), entry.filemode())?;
                }
            }
            // Skip submodule commit pointers, tags, and any other unexpected
            // object types that can appear as tree entries.
            _ => continue,
        }
    }

    let tree_oid = builder.write()?;
    repo.find_tree(tree_oid)
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::fs;
    use std::path::PathBuf;

    fn setup_test_repo() -> (Repository, PathBuf) {
        let thread_id = std::thread::current().id();
        let temp_path = std::env::temp_dir().join(format!("git-filter-tree-test-{:?}", thread_id));
        let _ = fs::remove_dir_all(&temp_path);
        fs::create_dir_all(&temp_path).unwrap();
        let repo = Repository::init_bare(&temp_path).unwrap();
        (repo, temp_path)
    }

    fn cleanup_test_repo(path: PathBuf) {
        let _ = fs::remove_dir_all(path);
    }

    fn create_test_tree<'a>(repo: &'a Repository) -> Result<git2::Tree<'a>, Error> {
        let mut tree_builder = repo.treebuilder(None)?;

        // Create some blob entries
        let blob1 = repo.blob(b"content1")?;
        let blob2 = repo.blob(b"content2")?;
        let blob3 = repo.blob(b"content3")?;

        tree_builder.insert("file1.txt", blob1, 0o100644)?;
        tree_builder.insert("file2.rs", blob2, 0o100644)?;
        tree_builder.insert("test.md", blob3, 0o100644)?;

        let tree_oid = tree_builder.write()?;
        repo.find_tree(tree_oid)
    }

    #[test]
    fn test_filter_single_pattern() -> Result<(), Error> {
        let (repo, temp_path) = setup_test_repo();

        let tree = create_test_tree(&repo)?;
        assert_eq!(tree.len(), 3);

        // Filter for .txt files only
        let filtered = repo.filter_by_patterns(&tree, &["*.txt"])?;
        assert_eq!(filtered.len(), 1);
        assert!(filtered.get_name("file1.txt").is_some());
        assert!(filtered.get_name("file2.rs").is_none());
        assert!(filtered.get_name("test.md").is_none());

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_multiple_patterns() -> Result<(), Error> {
        let (repo, temp_path) = setup_test_repo();

        let tree = create_test_tree(&repo)?;

        // Filter for .txt and .rs files
        let filtered = repo.filter_by_patterns(&tree, &["*.txt", "*.rs"])?;
        assert_eq!(filtered.len(), 2);
        assert!(filtered.get_name("file1.txt").is_some());
        assert!(filtered.get_name("file2.rs").is_some());
        assert!(filtered.get_name("test.md").is_none());

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_exact_match() -> Result<(), Error> {
        let (repo, temp_path) = setup_test_repo();

        let tree = create_test_tree(&repo)?;

        // Filter for exact filename
        let filtered = repo.filter_by_patterns(&tree, &["file1.txt"])?;
        assert_eq!(filtered.len(), 1);
        assert!(filtered.get_name("file1.txt").is_some());

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_wildcard_patterns() -> Result<(), Error> {
        let (repo, temp_path) = setup_test_repo();

        let tree = create_test_tree(&repo)?;

        // Filter with wildcard pattern
        let filtered = repo.filter_by_patterns(&tree, &["file*"])?;
        assert_eq!(filtered.len(), 2);
        assert!(filtered.get_name("file1.txt").is_some());
        assert!(filtered.get_name("file2.rs").is_some());
        assert!(filtered.get_name("test.md").is_none());

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_no_matches() -> Result<(), Error> {
        let (repo, temp_path) = setup_test_repo();

        let tree = create_test_tree(&repo)?;

        // Filter with pattern that matches nothing
        let filtered = repo.filter_by_patterns(&tree, &["*.nonexistent"])?;
        assert_eq!(filtered.len(), 0);

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_all_matches() -> Result<(), Error> {
        let (repo, temp_path) = setup_test_repo();

        let tree = create_test_tree(&repo)?;

        // Filter with pattern that matches everything
        let filtered = repo.filter_by_patterns(&tree, &["*"])?;
        assert_eq!(filtered.len(), 3);

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_empty_patterns_error() {
        let (repo, temp_path) = setup_test_repo();

        let tree = create_test_tree(&repo).unwrap();

        // Empty patterns should return an error
        let result = repo.filter_by_patterns(&tree, &[]);
        assert!(result.is_err());
        assert_eq!(
            result.unwrap_err().message(),
            "At least one pattern is required"
        );

        cleanup_test_repo(temp_path);
    }

    #[test]
    fn test_filter_invalid_pattern_error() {
        let (repo, temp_path) = setup_test_repo();

        let tree = create_test_tree(&repo).unwrap();

        // Invalid glob pattern should return an error
        let result = repo.filter_by_patterns(&tree, &["[invalid"]);
        assert!(result.is_err());

        cleanup_test_repo(temp_path);
    }

    #[test]
    fn test_filter_with_nested_tree() -> Result<(), Error> {
        let (repo, temp_path) = setup_test_repo();

        let mut tree_builder = repo.treebuilder(None)?;

        // Create a nested tree
        let mut subtree_builder = repo.treebuilder(None)?;
        let blob = repo.blob(b"nested content")?;
        subtree_builder.insert("nested.txt", blob, 0o100644)?;
        let subtree_oid = subtree_builder.write()?;

        // Add files and subtree to main tree
        let blob1 = repo.blob(b"content1")?;
        tree_builder.insert("file1.txt", blob1, 0o100644)?;
        tree_builder.insert("subdir", subtree_oid, 0o040000)?;

        let tree_oid = tree_builder.write()?;
        let tree = repo.find_tree(tree_oid)?;

        // Filter - should keep both file and directory
        let filtered = repo.filter_by_patterns(&tree, &["*"])?;
        assert_eq!(filtered.len(), 2);

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_preserves_empty_tree() -> Result<(), Error> {
        let (repo, temp_path) = setup_test_repo();

        // Create an empty tree
        let tree_builder = repo.treebuilder(None)?;
        let tree_oid = tree_builder.write()?;
        let tree = repo.find_tree(tree_oid)?;

        assert_eq!(tree.len(), 0);

        // Filter empty tree
        let filtered = repo.filter_by_patterns(&tree, &["*"])?;
        assert_eq!(filtered.len(), 0);

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_case_sensitive() -> Result<(), Error> {
        let (repo, temp_path) = setup_test_repo();

        let mut tree_builder = repo.treebuilder(None)?;
        let blob1 = repo.blob(b"content1")?;
        let blob2 = repo.blob(b"content2")?;

        tree_builder.insert("File.txt", blob1, 0o100644)?;
        tree_builder.insert("file.txt", blob2, 0o100644)?;

        let tree_oid = tree_builder.write()?;
        let tree = repo.find_tree(tree_oid)?;

        // Filter with exact case match
        let filtered = repo.filter_by_patterns(&tree, &["file.txt"])?;
        assert_eq!(filtered.len(), 1);
        assert!(filtered.get_name("file.txt").is_some());

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_complex_patterns() -> Result<(), Error> {
        let (repo, temp_path) = setup_test_repo();

        let mut tree_builder = repo.treebuilder(None)?;
        let blob = repo.blob(b"content")?;

        tree_builder.insert("test1.txt", blob, 0o100644)?;
        tree_builder.insert("test2.rs", blob, 0o100644)?;
        tree_builder.insert("data.json", blob, 0o100644)?;
        tree_builder.insert("README.md", blob, 0o100644)?;

        let tree_oid = tree_builder.write()?;
        let tree = repo.find_tree(tree_oid)?;

        // Multiple patterns with different wildcards
        let filtered = repo.filter_by_patterns(&tree, &["test*", "*.md"])?;
        assert_eq!(filtered.len(), 3);
        assert!(filtered.get_name("test1.txt").is_some());
        assert!(filtered.get_name("test2.rs").is_some());
        assert!(filtered.get_name("README.md").is_some());
        assert!(filtered.get_name("data.json").is_none());

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_trailing_slash_matches_directory_contents() -> Result<(), Error> {
        let (repo, temp_path) = setup_test_repo();

        // Build a tree with a subdirectory: pyo3/Cargo.toml, pyo3/src/lib.rs,
        // and a top-level file that should NOT match.
        let blob = repo.blob(b"content")?;

        let mut src_builder = repo.treebuilder(None)?;
        src_builder.insert("lib.rs", blob, 0o100644)?;
        let src_oid = src_builder.write()?;

        let mut pyo3_builder = repo.treebuilder(None)?;
        pyo3_builder.insert("Cargo.toml", blob, 0o100644)?;
        pyo3_builder.insert("src", src_oid, 0o040000)?;
        let pyo3_oid = pyo3_builder.write()?;

        let mut root_builder = repo.treebuilder(None)?;
        root_builder.insert("pyo3", pyo3_oid, 0o040000)?;
        root_builder.insert("README.md", blob, 0o100644)?;
        let root_oid = root_builder.write()?;
        let tree = repo.find_tree(root_oid)?;

        // "pyo3/" (trailing slash) must match all files under pyo3/.
        let filtered = repo.filter_by_patterns(&tree, &["pyo3/"])?;
        assert_eq!(filtered.len(), 1, "only the pyo3 dir should remain");
        assert!(filtered.get_name("pyo3").is_some());
        assert!(filtered.get_name("README.md").is_none());

        // The pyo3 subtree itself must retain both entries.
        let pyo3_entry = filtered.get_name("pyo3").unwrap();
        let pyo3_tree = repo.find_tree(pyo3_entry.id())?;
        assert!(pyo3_tree.get_name("Cargo.toml").is_some());
        assert!(pyo3_tree.get_name("src").is_some());

        cleanup_test_repo(temp_path);
        Ok(())
    }

    // -----------------------------------------------------------------------
    // Helpers and tests for filter_by_attributes
    // -----------------------------------------------------------------------

    /// Initializes a non-bare repository so that `.gitattributes` written to
    /// its working directory are picked up by `repo.get_attr(…)`.
    fn setup_attr_test_repo() -> (Repository, PathBuf) {
        let thread_id = std::thread::current().id();
        let temp_path = std::env::temp_dir().join(format!("git-filter-attr-test-{:?}", thread_id));
        let _ = fs::remove_dir_all(&temp_path);
        fs::create_dir_all(&temp_path).unwrap();
        let repo = Repository::init(&temp_path).unwrap();
        (repo, temp_path)
    }

    fn write_gitattributes(repo_path: &Path, content: &str) {
        fs::write(repo_path.join(".gitattributes"), content).unwrap();
    }

    // --- filter_by_attributes: error cases ---------------------------------

    #[test]
    fn test_filter_by_attributes_empty_returns_error() {
        let (repo, temp_path) = setup_attr_test_repo();
        write_gitattributes(&temp_path, "");

        let tree = create_test_tree(&repo).unwrap();
        let result = repo.filter_by_attributes(&tree, &[]);
        assert!(result.is_err());
        assert_eq!(
            result.unwrap_err().message(),
            "at least one attribute is required"
        );

        cleanup_test_repo(temp_path);
    }

    // --- filter_by_attributes: single attribute ----------------------------

    #[test]
    fn test_filter_by_attributes_set_attribute_includes_matching_files() -> Result<(), Error> {
        let (repo, temp_path) = setup_attr_test_repo();
        // Only .txt files carry the export-ignore attribute.
        write_gitattributes(&temp_path, "*.txt export-ignore\n");

        let blob = repo.blob(b"content")?;
        let mut builder = repo.treebuilder(None)?;
        builder.insert("readme.txt", blob, 0o100644)?;
        builder.insert("main.rs", blob, 0o100644)?;
        builder.insert("data.json", blob, 0o100644)?;
        let tree = repo.find_tree(builder.write()?)?;

        let filtered = repo.filter_by_attributes(&tree, &["export-ignore"])?;
        assert_eq!(filtered.len(), 1);
        assert!(filtered.get_name("readme.txt").is_some());
        assert!(filtered.get_name("main.rs").is_none());
        assert!(filtered.get_name("data.json").is_none());

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_by_attributes_explicitly_unset_attribute_excluded() -> Result<(), Error> {
        let (repo, temp_path) = setup_attr_test_repo();
        // .txt gets the attribute; .md explicitly has it unset with `-`.
        write_gitattributes(&temp_path, "*.txt custom-attr\n*.md -custom-attr\n");

        let blob = repo.blob(b"content")?;
        let mut builder = repo.treebuilder(None)?;
        builder.insert("readme.txt", blob, 0o100644)?;
        builder.insert("notes.md", blob, 0o100644)?;
        builder.insert("main.rs", blob, 0o100644)?;
        let tree = repo.find_tree(builder.write()?)?;

        let filtered = repo.filter_by_attributes(&tree, &["custom-attr"])?;
        // .txt is set, .md is explicitly unset, .rs is unspecified
        assert_eq!(filtered.len(), 1);
        assert!(filtered.get_name("readme.txt").is_some());
        assert!(filtered.get_name("notes.md").is_none());
        assert!(filtered.get_name("main.rs").is_none());

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_by_attributes_no_attributes_set_returns_empty_tree() -> Result<(), Error> {
        let (repo, temp_path) = setup_attr_test_repo();
        // Empty .gitattributes — nothing is attributed.
        write_gitattributes(&temp_path, "");

        let blob = repo.blob(b"content")?;
        let mut builder = repo.treebuilder(None)?;
        builder.insert("file.txt", blob, 0o100644)?;
        builder.insert("file.rs", blob, 0o100644)?;
        let tree = repo.find_tree(builder.write()?)?;

        let filtered = repo.filter_by_attributes(&tree, &["export-ignore"])?;
        assert_eq!(filtered.len(), 0);

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_by_attributes_multiple_attributes_all_required() -> Result<(), Error> {
        let (repo, temp_path) = setup_attr_test_repo();
        // .txt has both attributes; .rs has only one.
        write_gitattributes(&temp_path, "*.txt attr-a attr-b\n*.rs attr-a\n");

        let blob = repo.blob(b"content")?;
        let mut builder = repo.treebuilder(None)?;
        builder.insert("file.txt", blob, 0o100644)?;
        builder.insert("file.rs", blob, 0o100644)?;
        builder.insert("file.md", blob, 0o100644)?;
        let tree = repo.find_tree(builder.write()?)?;

        // Both attributes must be present for a file to be included.
        let filtered = repo.filter_by_attributes(&tree, &["attr-a", "attr-b"])?;
        assert_eq!(filtered.len(), 1);
        assert!(filtered.get_name("file.txt").is_some());
        assert!(filtered.get_name("file.rs").is_none());
        assert!(filtered.get_name("file.md").is_none());

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_by_attributes_attribute_with_value() -> Result<(), Error> {
        let (repo, temp_path) = setup_attr_test_repo();
        // linguist-language is set to a string value on .rs files.
        write_gitattributes(&temp_path, "*.rs linguist-language=Rust\n");

        let blob = repo.blob(b"content")?;
        let mut builder = repo.treebuilder(None)?;
        builder.insert("main.rs", blob, 0o100644)?;
        builder.insert("main.py", blob, 0o100644)?;
        let tree = repo.find_tree(builder.write()?)?;

        // An attribute with any value (including a string) counts as "set".
        let filtered = repo.filter_by_attributes(&tree, &["linguist-language"])?;
        assert_eq!(filtered.len(), 1);
        assert!(filtered.get_name("main.rs").is_some());
        assert!(filtered.get_name("main.py").is_none());

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_by_attributes_all_files_match() -> Result<(), Error> {
        let (repo, temp_path) = setup_attr_test_repo();
        // Wildcard rule sets the attribute on every file.
        write_gitattributes(&temp_path, "* generated\n");

        let blob = repo.blob(b"content")?;
        let mut builder = repo.treebuilder(None)?;
        builder.insert("a.txt", blob, 0o100644)?;
        builder.insert("b.rs", blob, 0o100644)?;
        builder.insert("c.md", blob, 0o100644)?;
        let tree = repo.find_tree(builder.write()?)?;

        let filtered = repo.filter_by_attributes(&tree, &["generated"])?;
        assert_eq!(filtered.len(), 3);

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_by_attributes_nested_tree_filters_recursively() -> Result<(), Error> {
        let (repo, temp_path) = setup_attr_test_repo();
        // Only .proto files carry the attribute.
        write_gitattributes(&temp_path, "*.proto linguist-generated\n");

        let blob = repo.blob(b"content")?;

        // src/api.proto and src/main.rs
        let mut src_builder = repo.treebuilder(None)?;
        src_builder.insert("api.proto", blob, 0o100644)?;
        src_builder.insert("main.rs", blob, 0o100644)?;
        let src_oid = src_builder.write()?;

        let mut root_builder = repo.treebuilder(None)?;
        root_builder.insert("src", src_oid, 0o040000)?;
        root_builder.insert("README.md", blob, 0o100644)?;
        let tree = repo.find_tree(root_builder.write()?)?;

        let filtered = repo.filter_by_attributes(&tree, &["linguist-generated"])?;

        // Top-level README.md must be gone; src/ must survive because it has
        // at least one matching descendant.
        assert_eq!(filtered.len(), 1);
        assert!(filtered.get_name("src").is_some());
        assert!(filtered.get_name("README.md").is_none());

        let src_entry = filtered.get_name("src").unwrap();
        let src_tree = repo.find_tree(src_entry.id())?;
        assert_eq!(src_tree.len(), 1);
        assert!(src_tree.get_name("api.proto").is_some());
        assert!(src_tree.get_name("main.rs").is_none());

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_by_attributes_empty_tree_stays_empty() -> Result<(), Error> {
        let (repo, temp_path) = setup_attr_test_repo();
        write_gitattributes(&temp_path, "* export-ignore\n");

        let tree = repo.find_tree(repo.treebuilder(None)?.write()?)?;
        assert_eq!(tree.len(), 0);

        let filtered = repo.filter_by_attributes(&tree, &["export-ignore"])?;
        assert_eq!(filtered.len(), 0);

        cleanup_test_repo(temp_path);
        Ok(())
    }

    #[test]
    fn test_filter_by_attributes_subdirectory_excluded_when_all_children_unmatched()
    -> Result<(), Error> {
        let (repo, temp_path) = setup_attr_test_repo();
        // Only .txt files match; the `docs/` sub-tree contains only .md files.
        write_gitattributes(&temp_path, "*.txt export-ignore\n");

        let blob = repo.blob(b"content")?;

        let mut docs_builder = repo.treebuilder(None)?;
        docs_builder.insert("guide.md", blob, 0o100644)?;
        docs_builder.insert("api.md", blob, 0o100644)?;
        let docs_oid = docs_builder.write()?;

        let mut root_builder = repo.treebuilder(None)?;
        root_builder.insert("docs", docs_oid, 0o040000)?;
        root_builder.insert("notes.txt", blob, 0o100644)?;
        let tree = repo.find_tree(root_builder.write()?)?;

        let filtered = repo.filter_by_attributes(&tree, &["export-ignore"])?;

        // `docs/` should be pruned entirely because none of its children matched.
        assert_eq!(filtered.len(), 1);
        assert!(filtered.get_name("notes.txt").is_some());
        assert!(filtered.get_name("docs").is_none());

        cleanup_test_repo(temp_path);
        Ok(())
    }
}