use crate::{    file::{self, File},    Graph, MAX_COMMITS,};use git_object::HashKind;use quick_error::quick_error;use std::{    io::{BufRead, BufReader},    path::{Path, PathBuf},}; quick_error! {    #[derive(Debug)]    pub enum Error {        File(err: file::Error, path: PathBuf) {            display("{}", path.display())            source(err)        }        HashVersionMismatch(path1: PathBuf, hash1: HashKind, path2: PathBuf, hash2: HashKind) {            display(                "Commit-graph files mismatch: '{}' uses hash {:?}, but '{}' uses hash {:?}",                path1.display(),                hash1,                path2.display(),                hash2,            )        }        Io(err: std::io::Error, path: PathBuf) {            display("Could not open commit-graph file at '{}'", path.display())            source(err)        }        TooManyCommits(num_commits: u64) {            display(                "Commit-graph files contain {} commits altogether, but only {} commits are allowed",                num_commits,                MAX_COMMITS,            )        }    }} /// Instantiate a `Graph` from various sourcesimpl Graph {    pub fn from_info_dir(info_dir: impl AsRef<Path>) -> Result<Self, Error> {        Self::from_single_file(info_dir.as_ref())            .or_else(|_| Self::from_split_chain(info_dir.as_ref().join("commit-graphs")))    }     pub fn from_single_file(info_dir: impl AsRef<Path>) -> Result<Self, Error> {        let single_graph_file = info_dir.as_ref().join("commit-graph");        let file = File::at(&single_graph_file).map_err(|e| Error::File(e, single_graph_file.clone()))?;        Self::new(vec![file])    }     pub fn from_split_chain(commit_graphs_dir: impl AsRef<Path>) -> Result<Self, Error> {        let commit_graphs_dir = commit_graphs_dir.as_ref();        let chain_file_path = commit_graphs_dir.join("commit-graph-chain");        let chain_file = std::fs::File::open(&chain_file_path).map_err(|e| Error::Io(e, chain_file_path.clone()))?;        let mut files = Vec::new();        for line in BufReader::new(chain_file).lines() {            let hash = line.map_err(|e| Error::Io(e, chain_file_path.clone()))?;            let graph_file_path = commit_graphs_dir.join(format!("graph-{}.graph", hash));            files.push(File::at(&graph_file_path).map_err(|e| Error::File(e, graph_file_path.clone()))?);        }        Self::new(files)    }     pub fn new(files: Vec<File>) -> Result<Self, Error> {        let num_commits: u64 = files.iter().map(|f| f.num_commits() as u64).sum();        if num_commits > MAX_COMMITS as u64 {            return Err(Error::TooManyCommits(num_commits));        }         for window in files.windows(2) {            let f1 = &window[0];            let f2 = &window[1];            if f1.hash_kind() != f2.hash_kind() {                return Err(Error::HashVersionMismatch(                    f1.path().to_owned(),                    f1.hash_kind(),                    f2.path().to_owned(),                    f2.hash_kind(),                ));            }        }         Ok(Self { files })    }}