use crate::{File, Graph, MAX_COMMITS};use gix_error::{message, ErrorExt, Exn, Message, ResultExt};use std::{    io::{BufRead, BufReader},    path::Path,}; /// Instantiate a `Graph` from various sources.impl Graph {    /// Instantiate a commit graph from `path` which may be a directory containing graph files or the graph file itself.    pub fn at(path: &Path) -> Result<Self, Exn<Message>> {        Self::try_from(path)    }     /// Instantiate a commit graph from the directory containing all of its files.    pub fn from_commit_graphs_dir(path: &Path) -> Result<Self, Exn<Message>> {        let commit_graphs_dir = path;        let chain_file_path = commit_graphs_dir.join("commit-graph-chain");        let chain_file = std::fs::File::open(&chain_file_path).or_raise(|| {            message!(                "Could not open commit-graph chain file at '{}'",                chain_file_path.display()            )        })?;        let mut files = Vec::new();        for line in BufReader::new(chain_file).lines() {            let hash = line.or_raise(|| {                message!(                    "Could not read from commit-graph file at '{}'",                    chain_file_path.display()                )            })?;            let graph_file_path = commit_graphs_dir.join(format!("graph-{hash}.graph"));            files.push(                File::at(&graph_file_path)                    .or_raise(|| message!("Could not open commit-graph file at '{}'", graph_file_path.display()))?,            );        }        Ok(Self::new(files)?)    }     /// Instantiate a commit graph from a `.git/objects/info/commit-graph` or    /// `.git/objects/info/commit-graphs/graph-*.graph` file.    pub fn from_file(path: &Path) -> Result<Self, Exn<Message>> {        let file = File::at(path).or_raise(|| message!("Could not open commit-graph file at '{}'", path.display()))?;        Ok(Self::new(vec![file])?)    }     /// Instantiate a commit graph from an `.git/objects/info` directory.    pub fn from_info_dir(info_dir: &Path) -> Result<Self, Exn<Message>> {        Self::from_file(&info_dir.join("commit-graph"))            .or_else(|_| Self::from_commit_graphs_dir(&info_dir.join("commit-graphs")))    }     /// Create a new commit graph from a list of `files`.    pub fn new(files: Vec<File>) -> Result<Self, Message> {        let files = nonempty::NonEmpty::from_vec(files)            .ok_or_else(|| message!("Commit-graph must contain at least one file"))?;        let num_commits: u64 = files.iter().map(|f| u64::from(f.num_commits())).sum();        if num_commits > u64::from(MAX_COMMITS) {            return Err(message!(                "Commit-graph files contain {num_commits} commits altogether, but only {MAX_COMMITS} commits are allowed"            ));        }         let mut f1 = files.first();        for f2 in files.tail() {            if f1.object_hash() != f2.object_hash() {                return Err(message!(                    "Commit-graph files mismatch: '{path1}' uses hash {hash1:?}, but '{path2}' uses hash {hash2:?}",                    path1 = f1.path().display(),                    hash1 = f1.object_hash(),                    path2 = f2.path().display(),                    hash2 = f2.object_hash(),                ));            }            f1 = f2;        }         Ok(Self { files })    }} impl TryFrom<&Path> for Graph {    type Error = Exn<Message>;     fn try_from(path: &Path) -> Result<Self, Self::Error> {        if path.is_file() {            // Assume we are looking at `.git/objects/info/commit-graph` or            // `.git/objects/info/commit-graphs/graph-*.graph`.            Self::from_file(path)        } else if path.is_dir() {            if path.join("commit-graph-chain").is_file() {                Self::from_commit_graphs_dir(path)            } else {                Self::from_info_dir(path)            }        } else {            Err(message!(                "Did not find any files that look like commit graphs at '{}'",                path.display()            )            .raise())        }    }}