view rust/hg-core/src/repo.rs @ 48409:005ae1a343f8

rhg: add support for narrow clones and sparse checkouts

This adds a minimal support that can be implemented without parsing the narrowspec.
We can parse the narrowspec and add support for more operations later.

The reason we need so few code changes is as follows:

Most operations need no special treatment of sparse because
some of them only read dirstate (`rhg files` without `-r`),
which bakes in the filtering,
some of them only read store (`rhg files -r`, `rhg cat`),
and some of them read no data at all (`rhg root`, `rhg debugrequirements`).

`status` is the command that might care about sparse, so we just disable
rhg on it.

For narrow clones, `rhg files` clearly needs the narrowspec to work
correctly, so we fall back.
`rhg cat` seems to work consistently with `hg cat` if the file exists.
If the file is hidden by narrow spec, the error message is different and confusing, so
that's something that we should improve in follow-up patches.

Differential Revision: https://phab.mercurial-scm.org/D11764

use crate::changelog::Changelog;
use crate::config::{Config, ConfigError, ConfigParseError};
use crate::dirstate::DirstateParents;
use crate::dirstate_tree::dirstate_map::DirstateMap;
use crate::dirstate_tree::owning::OwningDirstateMap;
use crate::errors::HgError;
use crate::errors::HgResultExt;
use crate::exit_codes;
use crate::manifest::{Manifest, Manifestlog};
use crate::revlog::filelog::Filelog;
use crate::revlog::revlog::RevlogError;
use crate::utils::files::get_path_from_bytes;
use crate::utils::hg_path::HgPath;
use crate::utils::SliceExt;
use crate::vfs::{is_dir, is_file, Vfs};
use crate::{requirements, NodePrefix};
use crate::{DirstateError, Revision};
use std::cell::{Cell, Ref, RefCell, RefMut};
use std::collections::HashSet;
use std::path::{Path, PathBuf};

/// A repository on disk
pub struct Repo {
    working_directory: PathBuf,
    dot_hg: PathBuf,
    store: PathBuf,
    requirements: HashSet<String>,
    config: Config,
    // None means not known/initialized yet
    dirstate_parents: Cell<Option<DirstateParents>>,
    dirstate_map: LazyCell<OwningDirstateMap, DirstateError>,
    changelog: LazyCell<Changelog, HgError>,
    manifestlog: LazyCell<Manifestlog, HgError>,
}

#[derive(Debug, derive_more::From)]
pub enum RepoError {
    NotFound {
        at: PathBuf,
    },
    #[from]
    ConfigParseError(ConfigParseError),
    #[from]
    Other(HgError),
}

impl From<ConfigError> for RepoError {
    fn from(error: ConfigError) -> Self {
        match error {
            ConfigError::Parse(error) => error.into(),
            ConfigError::Other(error) => error.into(),
        }
    }
}

impl Repo {
    /// tries to find nearest repository root in current working directory or
    /// its ancestors
    pub fn find_repo_root() -> Result<PathBuf, RepoError> {
        let current_directory = crate::utils::current_dir()?;
        // ancestors() is inclusive: it first yields `current_directory`
        // as-is.
        for ancestor in current_directory.ancestors() {
            if is_dir(ancestor.join(".hg"))? {
                return Ok(ancestor.to_path_buf());
            }
        }
        return Err(RepoError::NotFound {
            at: current_directory,
        });
    }

    /// Find a repository, either at the given path (which must contain a `.hg`
    /// sub-directory) or by searching the current directory and its
    /// ancestors.
    ///
    /// A method with two very different "modes" like this usually a code smell
    /// to make two methods instead, but in this case an `Option` is what rhg
    /// sub-commands get from Clap for the `-R` / `--repository` CLI argument.
    /// Having two methods would just move that `if` to almost all callers.
    pub fn find(
        config: &Config,
        explicit_path: Option<PathBuf>,
    ) -> Result<Self, RepoError> {
        if let Some(root) = explicit_path {
            if is_dir(root.join(".hg"))? {
                Self::new_at_path(root.to_owned(), config)
            } else if is_file(&root)? {
                Err(HgError::unsupported("bundle repository").into())
            } else {
                Err(RepoError::NotFound {
                    at: root.to_owned(),
                })
            }
        } else {
            let root = Self::find_repo_root()?;
            Self::new_at_path(root, config)
        }
    }

    /// To be called after checking that `.hg` is a sub-directory
    fn new_at_path(
        working_directory: PathBuf,
        config: &Config,
    ) -> Result<Self, RepoError> {
        let dot_hg = working_directory.join(".hg");

        let mut repo_config_files = Vec::new();
        repo_config_files.push(dot_hg.join("hgrc"));
        repo_config_files.push(dot_hg.join("hgrc-not-shared"));

        let hg_vfs = Vfs { base: &dot_hg };
        let mut reqs = requirements::load_if_exists(hg_vfs)?;
        let relative =
            reqs.contains(requirements::RELATIVE_SHARED_REQUIREMENT);
        let shared =
            reqs.contains(requirements::SHARED_REQUIREMENT) || relative;

        // From `mercurial/localrepo.py`:
        //
        // if .hg/requires contains the sharesafe requirement, it means
        // there exists a `.hg/store/requires` too and we should read it
        // NOTE: presence of SHARESAFE_REQUIREMENT imply that store requirement
        // is present. We never write SHARESAFE_REQUIREMENT for a repo if store
        // is not present, refer checkrequirementscompat() for that
        //
        // However, if SHARESAFE_REQUIREMENT is not present, it means that the
        // repository was shared the old way. We check the share source
        // .hg/requires for SHARESAFE_REQUIREMENT to detect whether the
        // current repository needs to be reshared
        let share_safe = reqs.contains(requirements::SHARESAFE_REQUIREMENT);

        let store_path;
        if !shared {
            store_path = dot_hg.join("store");
        } else {
            let bytes = hg_vfs.read("sharedpath")?;
            let mut shared_path =
                get_path_from_bytes(bytes.trim_end_matches(|b| b == b'\n'))
                    .to_owned();
            if relative {
                shared_path = dot_hg.join(shared_path)
            }
            if !is_dir(&shared_path)? {
                return Err(HgError::corrupted(format!(
                    ".hg/sharedpath points to nonexistent directory {}",
                    shared_path.display()
                ))
                .into());
            }

            store_path = shared_path.join("store");

            let source_is_share_safe =
                requirements::load(Vfs { base: &shared_path })?
                    .contains(requirements::SHARESAFE_REQUIREMENT);

            if share_safe && !source_is_share_safe {
                return Err(match config
                    .get(b"share", b"safe-mismatch.source-not-safe")
                {
                    Some(b"abort") | None => HgError::abort(
                        "abort: share source does not support share-safe requirement\n\
                        (see `hg help config.format.use-share-safe` for more information)",
                        exit_codes::ABORT,
                    ),
                    _ => HgError::unsupported("share-safe downgrade"),
                }
                .into());
            } else if source_is_share_safe && !share_safe {
                return Err(
                    match config.get(b"share", b"safe-mismatch.source-safe") {
                        Some(b"abort") | None => HgError::abort(
                            "abort: version mismatch: source uses share-safe \
                            functionality while the current share does not\n\
                            (see `hg help config.format.use-share-safe` for more information)",
                        exit_codes::ABORT,
                        ),
                        _ => HgError::unsupported("share-safe upgrade"),
                    }
                    .into(),
                );
            }

            if share_safe {
                repo_config_files.insert(0, shared_path.join("hgrc"))
            }
        }
        if share_safe {
            reqs.extend(requirements::load(Vfs { base: &store_path })?);
        }

        let repo_config = if std::env::var_os("HGRCSKIPREPO").is_none() {
            config.combine_with_repo(&repo_config_files)?
        } else {
            config.clone()
        };

        let repo = Self {
            requirements: reqs,
            working_directory,
            store: store_path,
            dot_hg,
            config: repo_config,
            dirstate_parents: Cell::new(None),
            dirstate_map: LazyCell::new(Self::new_dirstate_map),
            changelog: LazyCell::new(Changelog::open),
            manifestlog: LazyCell::new(Manifestlog::open),
        };

        requirements::check(&repo)?;

        Ok(repo)
    }

    pub fn working_directory_path(&self) -> &Path {
        &self.working_directory
    }

    pub fn requirements(&self) -> &HashSet<String> {
        &self.requirements
    }

    pub fn config(&self) -> &Config {
        &self.config
    }

    /// For accessing repository files (in `.hg`), except for the store
    /// (`.hg/store`).
    pub fn hg_vfs(&self) -> Vfs<'_> {
        Vfs { base: &self.dot_hg }
    }

    /// For accessing repository store files (in `.hg/store`)
    pub fn store_vfs(&self) -> Vfs<'_> {
        Vfs { base: &self.store }
    }

    /// For accessing the working copy
    pub fn working_directory_vfs(&self) -> Vfs<'_> {
        Vfs {
            base: &self.working_directory,
        }
    }

    pub fn has_dirstate_v2(&self) -> bool {
        self.requirements
            .contains(requirements::DIRSTATE_V2_REQUIREMENT)
    }

    pub fn has_sparse(&self) -> bool {
        self.requirements.contains(requirements::SPARSE_REQUIREMENT)
    }

    pub fn has_narrow(&self) -> bool {
        self.requirements.contains(requirements::NARROW_REQUIREMENT)
    }

    fn dirstate_file_contents(&self) -> Result<Vec<u8>, HgError> {
        Ok(self
            .hg_vfs()
            .read("dirstate")
            .io_not_found_as_none()?
            .unwrap_or(Vec::new()))
    }

    pub fn dirstate_parents(&self) -> Result<DirstateParents, HgError> {
        if let Some(parents) = self.dirstate_parents.get() {
            return Ok(parents);
        }
        let dirstate = self.dirstate_file_contents()?;
        let parents = if dirstate.is_empty() {
            DirstateParents::NULL
        } else if self.has_dirstate_v2() {
            crate::dirstate_tree::on_disk::read_docket(&dirstate)?.parents()
        } else {
            crate::dirstate::parsers::parse_dirstate_parents(&dirstate)?
                .clone()
        };
        self.dirstate_parents.set(Some(parents));
        Ok(parents)
    }

    fn new_dirstate_map(&self) -> Result<OwningDirstateMap, DirstateError> {
        let dirstate_file_contents = self.dirstate_file_contents()?;
        if dirstate_file_contents.is_empty() {
            self.dirstate_parents.set(Some(DirstateParents::NULL));
            Ok(OwningDirstateMap::new_empty(Vec::new()))
        } else if self.has_dirstate_v2() {
            let docket = crate::dirstate_tree::on_disk::read_docket(
                &dirstate_file_contents,
            )?;
            self.dirstate_parents.set(Some(docket.parents()));
            let data_size = docket.data_size();
            let metadata = docket.tree_metadata();
            let mut map = if let Some(data_mmap) = self
                .hg_vfs()
                .mmap_open(docket.data_filename())
                .io_not_found_as_none()?
            {
                OwningDirstateMap::new_empty(data_mmap)
            } else {
                OwningDirstateMap::new_empty(Vec::new())
            };
            let (on_disk, placeholder) = map.get_pair_mut();
            *placeholder = DirstateMap::new_v2(on_disk, data_size, metadata)?;
            Ok(map)
        } else {
            let mut map = OwningDirstateMap::new_empty(dirstate_file_contents);
            let (on_disk, placeholder) = map.get_pair_mut();
            let (inner, parents) = DirstateMap::new_v1(on_disk)?;
            self.dirstate_parents
                .set(Some(parents.unwrap_or(DirstateParents::NULL)));
            *placeholder = inner;
            Ok(map)
        }
    }

    pub fn dirstate_map(
        &self,
    ) -> Result<Ref<OwningDirstateMap>, DirstateError> {
        self.dirstate_map.get_or_init(self)
    }

    pub fn dirstate_map_mut(
        &self,
    ) -> Result<RefMut<OwningDirstateMap>, DirstateError> {
        self.dirstate_map.get_mut_or_init(self)
    }

    pub fn changelog(&self) -> Result<Ref<Changelog>, HgError> {
        self.changelog.get_or_init(self)
    }

    pub fn changelog_mut(&self) -> Result<RefMut<Changelog>, HgError> {
        self.changelog.get_mut_or_init(self)
    }

    pub fn manifestlog(&self) -> Result<Ref<Manifestlog>, HgError> {
        self.manifestlog.get_or_init(self)
    }

    pub fn manifestlog_mut(&self) -> Result<RefMut<Manifestlog>, HgError> {
        self.manifestlog.get_mut_or_init(self)
    }

    /// Returns the manifest of the *changeset* with the given node ID
    pub fn manifest_for_node(
        &self,
        node: impl Into<NodePrefix>,
    ) -> Result<Manifest, RevlogError> {
        self.manifestlog()?.data_for_node(
            self.changelog()?
                .data_for_node(node.into())?
                .manifest_node()?
                .into(),
        )
    }

    /// Returns the manifest of the *changeset* with the given revision number
    pub fn manifest_for_rev(
        &self,
        revision: Revision,
    ) -> Result<Manifest, RevlogError> {
        self.manifestlog()?.data_for_node(
            self.changelog()?
                .data_for_rev(revision)?
                .manifest_node()?
                .into(),
        )
    }

    pub fn filelog(&self, path: &HgPath) -> Result<Filelog, HgError> {
        Filelog::open(self, path)
    }
}

/// Lazily-initialized component of `Repo` with interior mutability
///
/// This differs from `OnceCell` in that the value can still be "deinitialized"
/// later by setting its inner `Option` to `None`.
struct LazyCell<T, E> {
    value: RefCell<Option<T>>,
    // `Fn`s that don’t capture environment are zero-size, so this box does
    // not allocate:
    init: Box<dyn Fn(&Repo) -> Result<T, E>>,
}

impl<T, E> LazyCell<T, E> {
    fn new(init: impl Fn(&Repo) -> Result<T, E> + 'static) -> Self {
        Self {
            value: RefCell::new(None),
            init: Box::new(init),
        }
    }

    fn get_or_init(&self, repo: &Repo) -> Result<Ref<T>, E> {
        let mut borrowed = self.value.borrow();
        if borrowed.is_none() {
            drop(borrowed);
            // Only use `borrow_mut` if it is really needed to avoid panic in
            // case there is another outstanding borrow but mutation is not
            // needed.
            *self.value.borrow_mut() = Some((self.init)(repo)?);
            borrowed = self.value.borrow()
        }
        Ok(Ref::map(borrowed, |option| option.as_ref().unwrap()))
    }

    pub fn get_mut_or_init(&self, repo: &Repo) -> Result<RefMut<T>, E> {
        let mut borrowed = self.value.borrow_mut();
        if borrowed.is_none() {
            *borrowed = Some((self.init)(repo)?);
        }
        Ok(RefMut::map(borrowed, |option| option.as_mut().unwrap()))
    }
}