view rust/hg-core/src/repo.rs @ 46472:98e39f04d60e

upgrade: implement partial upgrade for upgrading persistent-nodemap

Upgrading repositories to use persistent nodemap should be fast and easy as it
requires only two things:

1) Updating the requirements
2) Writing a persistent-nodemap on disk

For both of the steps above, we don't need to edit existing revlogs.

This patch makes upgrade only do the above mentioned two steps if we are
only upgarding to use persistent-nodemap feature.

Since `nodemap.persist_nodemap()` assumes that there exists a nodemap file for
the given revlog if we are trying to call it, this patch adds `force` argument
to create a file if does not exist which is true in our upgrade case.

The test changes demonstrate that we no longer write nodemap files for manifest
after upgrade which I think is desirable.

Differential Revision: https://phab.mercurial-scm.org/D9936

use crate::errors::{HgError, IoResultExt};
use crate::requirements;
use crate::utils::files::get_path_from_bytes;
use memmap::{Mmap, MmapOptions};
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>,
}

#[derive(Debug, derive_more::From)]
pub enum RepoFindError {
    NotFoundInCurrentDirectoryOrAncestors {
        current_directory: PathBuf,
    },
    #[from]
    Other(HgError),
}

/// Filesystem access abstraction for the contents of a given "base" diretory
#[derive(Clone, Copy)]
pub(crate) struct Vfs<'a> {
    base: &'a Path,
}

impl Repo {
    /// Search the current directory and its ancestores for a repository:
    /// a working directory that contains a `.hg` sub-directory.
    pub fn find() -> Result<Self, RepoFindError> {
        let current_directory = crate::utils::current_dir()?;
        // ancestors() is inclusive: it first yields `current_directory` as-is.
        for ancestor in current_directory.ancestors() {
            if ancestor.join(".hg").is_dir() {
                return Ok(Self::new_at_path(ancestor.to_owned())?);
            }
        }
        Err(RepoFindError::NotFoundInCurrentDirectoryOrAncestors {
            current_directory,
        })
    }

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

        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");
            if share_safe {
                reqs.extend(requirements::load(Vfs { base: &store_path })?);
            }
        } else {
            let bytes = hg_vfs.read("sharedpath")?;
            let mut shared_path = get_path_from_bytes(&bytes).to_owned();
            if relative {
                shared_path = dot_hg.join(shared_path)
            }
            if !shared_path.is_dir() {
                return Err(HgError::corrupted(format!(
                    ".hg/sharedpath points to nonexistent directory {}",
                    shared_path.display()
                )));
            }

            store_path = shared_path.join("store");

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

            // TODO: support for `share.safe-mismatch.*` config
            if share_safe && !source_is_share_safe {
                return Err(HgError::unsupported("share-safe downgrade"));
            } else if source_is_share_safe && !share_safe {
                return Err(HgError::unsupported("share-safe upgrade"));
            }
        }

        let repo = Self {
            requirements: reqs,
            working_directory,
            store: store_path,
            dot_hg,
        };

        requirements::check(&repo)?;

        Ok(repo)
    }

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

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

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

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

    /// For accessing the working copy

    // The undescore prefix silences the "never used" warning. Remove before
    // using.
    pub(crate) fn _working_directory_vfs(&self) -> Vfs<'_> {
        Vfs {
            base: &self.working_directory,
        }
    }
}

impl Vfs<'_> {
    pub(crate) fn join(&self, relative_path: impl AsRef<Path>) -> PathBuf {
        self.base.join(relative_path)
    }

    pub(crate) fn read(
        &self,
        relative_path: impl AsRef<Path>,
    ) -> Result<Vec<u8>, HgError> {
        let path = self.join(relative_path);
        std::fs::read(&path).for_file(&path)
    }

    pub(crate) fn mmap_open(
        &self,
        relative_path: impl AsRef<Path>,
    ) -> Result<Mmap, HgError> {
        let path = self.base.join(relative_path);
        let file = std::fs::File::open(&path).for_file(&path)?;
        // TODO: what are the safety requirements here?
        let mmap = unsafe { MmapOptions::new().map(&file) }.for_file(&path)?;
        Ok(mmap)
    }
}