rhg: Initial support for the 'status' command

Only comparing the working directory with its first parent revision
is supported. The core logic of dirstate handling and `stat`’ing files
was already in `hg-core` supporting Python-based hg with Rust extensions,
so this is mostly plumbing to rhg’s CLI.

For now the command is experimental and disabled by default,
since it has some bugs that causes a number of tests to fail.
These failures can be seen with:

  tests/run-tests.py --rhg --extra-config-opt rhg.status=true

Differential Revision: https://phab.mercurial-scm.org/D10239

rust/rhg/src/commands/status.rs

@@ -0,0 +1,315 b''
+// status.rs
+//
+// Copyright 2020, Georges Racinet <[e-mail]>
+//
+// This software may be used and distributed according to the terms of the
+// GNU General Public License version 2 or any later version.
+
+use crate::error::CommandError;
+use crate::ui::Ui;
+use clap::{Arg, SubCommand};
+use hg;
+use hg::errors::IoResultExt;
+use hg::matchers::AlwaysMatcher;
+use hg::operations::cat;
+use hg::repo::Repo;
+use hg::revlog::node::Node;
+use hg::utils::hg_path::{hg_path_to_os_string, HgPath};
+use hg::{DirstateMap, StatusError};
+use hg::{HgPathCow, StatusOptions};
+use log::{info, warn};
+use std::convert::TryInto;
+use std::fs;
+use std::io::BufReader;
+use std::io::Read;
+
+pub const HELP_TEXT: &str = "
+Show changed files in the working directory
+
+This is a pure Rust version of `hg status`.
+
+Some options might be missing, check the list below.
+";
+
+pub fn args() -> clap::App<'static, 'static> {
+    SubCommand::with_name("status")
+        .alias("st")
+        .about(HELP_TEXT)
+        .arg(
+            Arg::with_name("all")
+                .help("show status of all files")
+                .short("-A")
+                .long("--all"),
+        )
+        .arg(
+            Arg::with_name("modified")
+                .help("show only modified files")
+                .short("-m")
+                .long("--modified"),
+        )
+        .arg(
+            Arg::with_name("added")
+                .help("show only added files")
+                .short("-a")
+                .long("--added"),
+        )
+        .arg(
+            Arg::with_name("removed")
+                .help("show only removed files")
+                .short("-r")
+                .long("--removed"),
+        )
+        .arg(
+            Arg::with_name("clean")
+                .help("show only clean files")
+                .short("-c")
+                .long("--clean"),
+        )
+        .arg(
+            Arg::with_name("deleted")
+                .help("show only deleted files")
+                .short("-d")
+                .long("--deleted"),
+        )
+        .arg(
+            Arg::with_name("unknown")
+                .help("show only unknown (not tracked) files")
+                .short("-u")
+                .long("--unknown"),
+        )
+        .arg(
+            Arg::with_name("ignored")
+                .help("show only ignored files")
+                .short("-i")
+                .long("--ignored"),
+        )
+}
+
+/// Pure data type allowing the caller to specify file states to display
+#[derive(Copy, Clone, Debug)]
+pub struct DisplayStates {
+    pub modified: bool,
+    pub added: bool,
+    pub removed: bool,
+    pub clean: bool,
+    pub deleted: bool,
+    pub unknown: bool,
+    pub ignored: bool,
+}
+
+pub const DEFAULT_DISPLAY_STATES: DisplayStates = DisplayStates {
+    modified: true,
+    added: true,
+    removed: true,
+    clean: false,
+    deleted: true,
+    unknown: true,
+    ignored: false,
+};
+
+pub const ALL_DISPLAY_STATES: DisplayStates = DisplayStates {
+    modified: true,
+    added: true,
+    removed: true,
+    clean: true,
+    deleted: true,
+    unknown: true,
+    ignored: true,
+};
+
+impl DisplayStates {
+    pub fn is_empty(&self) -> bool {
+        !(self.modified
+            || self.added
+            || self.removed
+            || self.clean
+            || self.deleted
+            || self.unknown
+            || self.ignored)
+    }
+}
+
+pub fn run(invocation: &crate::CliInvocation) -> Result<(), CommandError> {
+    let status_enabled_default = false;
+    let status_enabled = invocation.config.get_option(b"rhg", b"status")?;
+    if !status_enabled.unwrap_or(status_enabled_default) {
+        return Err(CommandError::unsupported(
+            "status is experimental in rhg (enable it with 'rhg.status = true' \
+            or enable fallback with 'rhg.on-unsupported = fallback')"
+        ));
+    }
+
+    let ui = invocation.ui;
+    let args = invocation.subcommand_args;
+    let display_states = if args.is_present("all") {
+        // TODO when implementing `--quiet`: it excludes clean files
+        // from `--all`
+        ALL_DISPLAY_STATES
+    } else {
+        let requested = DisplayStates {
+            modified: args.is_present("modified"),
+            added: args.is_present("added"),
+            removed: args.is_present("removed"),
+            clean: args.is_present("clean"),
+            deleted: args.is_present("deleted"),
+            unknown: args.is_present("unknown"),
+            ignored: args.is_present("ignored"),
+        };
+        if requested.is_empty() {
+            DEFAULT_DISPLAY_STATES
+        } else {
+            requested
+        }
+    };
+
+    let repo = invocation.repo?;
+    let mut dmap = DirstateMap::new();
+    let dirstate_data = repo.hg_vfs().mmap_open("dirstate")?;
+    let parents = dmap.read(&dirstate_data)?;
+    let options = StatusOptions {
+        // TODO should be provided by the dirstate parsing and
+        // hence be stored on dmap. Using a value that assumes we aren't
+        // below the time resolution granularity of the FS and the
+        // dirstate.
+        last_normal_time: 0,
+        // we're currently supporting file systems with exec flags only
+        // anyway
+        check_exec: true,
+        list_clean: display_states.clean,
+        list_unknown: display_states.unknown,
+        list_ignored: display_states.ignored,
+        collect_traversed_dirs: false,
+    };
+    let ignore_file = repo.working_directory_vfs().join(".hgignore"); // TODO hardcoded
+    let ((lookup, ds_status), pattern_warnings) = hg::status(
+        &dmap,
+        &AlwaysMatcher,
+        repo.working_directory_path().to_owned(),
+        vec![ignore_file],
+        options,
+    )?;
+    if !pattern_warnings.is_empty() {
+        warn!("Pattern warnings: {:?}", &pattern_warnings);
+    }
+
+    if !ds_status.bad.is_empty() {
+        warn!("Bad matches {:?}", &(ds_status.bad))
+    }
+    if !lookup.is_empty() {
+        info!(
+            "Files to be rechecked by retrieval from filelog: {:?}",
+            &lookup
+        );
+    }
+    // TODO check ordering to match `hg status` output.
+    // (this is as in `hg help status`)
+    if display_states.modified {
+        display_status_paths(ui, &(ds_status.modified), b"M")?;
+    }
+    if !lookup.is_empty() {
+        let p1: Node = parents
+            .expect(
+                "Dirstate with no parents should not list any file to
+                 be rechecked for modifications",
+            )
+            .p1
+            .into();
+        let p1_hex = format!("{:x}", p1);
+        let mut rechecked_modified: Vec<HgPathCow> = Vec::new();
+        let mut rechecked_clean: Vec<HgPathCow> = Vec::new();
+        for to_check in lookup {
+            if cat_file_is_modified(repo, &to_check, &p1_hex)? {
+                rechecked_modified.push(to_check);
+            } else {
+                rechecked_clean.push(to_check);
+            }
+        }
+        if display_states.modified {
+            display_status_paths(ui, &rechecked_modified, b"M")?;
+        }
+        if display_states.clean {
+            display_status_paths(ui, &rechecked_clean, b"C")?;
+        }
+    }
+    if display_states.added {
+        display_status_paths(ui, &(ds_status.added), b"A")?;
+    }
+    if display_states.clean {
+        display_status_paths(ui, &(ds_status.clean), b"C")?;
+    }
+    if display_states.removed {
+        display_status_paths(ui, &(ds_status.removed), b"R")?;
+    }
+    if display_states.deleted {
+        display_status_paths(ui, &(ds_status.deleted), b"!")?;
+    }
+    if display_states.unknown {
+        display_status_paths(ui, &(ds_status.unknown), b"?")?;
+    }
+    if display_states.ignored {
+        display_status_paths(ui, &(ds_status.ignored), b"I")?;
+    }
+    Ok(())
+}
+
+// Probably more elegant to use a Deref or Borrow trait rather than
+// harcode HgPathBuf, but probably not really useful at this point
+fn display_status_paths(
+    ui: &Ui,
+    paths: &[HgPathCow],
+    status_prefix: &[u8],
+) -> Result<(), CommandError> {
+    for path in paths {
+        // Same TODO as in commands::root
+        let bytes: &[u8] = path.as_bytes();
+        // TODO optim, probably lots of unneeded copies here, especially
+        // if out stream is buffered
+        ui.write_stdout(&[status_prefix, b" ", bytes, b"\n"].concat())?;
+    }
+    Ok(())
+}
+
+/// Check if a file is modified by comparing actual repo store and file system.
+///
+/// This meant to be used for those that the dirstate cannot resolve, due
+/// to time resolution limits.
+///
+/// TODO: detect permission bits and similar metadata modifications
+fn cat_file_is_modified(
+    repo: &Repo,
+    hg_path: &HgPath,
+    rev: &str,
+) -> Result<bool, CommandError> {
+    // TODO CatRev expects &[HgPathBuf], something like
+    // &[impl Deref<HgPath>] would be nicer and should avoid the copy
+    let path_bufs = [hg_path.into()];
+    // TODO IIUC CatRev returns a simple Vec<u8> for all files
+    //      being able to tell them apart as (path, bytes) would be nicer
+    //      and OPTIM would allow manifest resolution just once.
+    let output = cat(repo, rev, &path_bufs).map_err(|e| (e, rev))?;
+
+    let fs_path = repo
+        .working_directory_vfs()
+        .join(hg_path_to_os_string(hg_path).expect("HgPath conversion"));
+    let hg_data_len: u64 = match output.concatenated.len().try_into() {
+        Ok(v) => v,
+        Err(_) => {
+            // conversion of data length to u64 failed,
+            // good luck for any file to have this content
+            return Ok(true);
+        }
+    };
+    let fobj = fs::File::open(&fs_path).when_reading_file(&fs_path)?;
+    if fobj.metadata().map_err(|e| StatusError::from(e))?.len() != hg_data_len
+    {
+        return Ok(true);
+    }
+    for (fs_byte, hg_byte) in
+        BufReader::new(fobj).bytes().zip(output.concatenated)
+    {
+        if fs_byte.map_err(|e| StatusError::from(e))? != hg_byte {
+            return Ok(true);
+        }
+    }
+    Ok(false)
+}

rust/hg-core/src/repo.rs

@@ -1,269 +1,266 b''
 use crate::config::{Config, ConfigError, ConfigParseError};
 use crate::errors::{HgError, IoErrorContext, IoResultExt};
 use crate::requirements;
 use crate::utils::files::get_path_from_bytes;
 use crate::utils::SliceExt;
 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>,
     config: Config,
 }
 
 #[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(),
         }
     }
 }
 
 /// Filesystem access abstraction for the contents of a given "base" diretory
 #[derive(Clone, Copy)]
 pub struct Vfs<'a> {
     pub(crate) base: &'a Path,
 }
 
 impl Repo {
     /// 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<&Path>,
     ) -> Result<Self, RepoError> {
         if let Some(root) = explicit_path {
             if root.join(".hg").is_dir() {
                 Self::new_at_path(root.to_owned(), config)
             } else if root.is_file() {
                 Err(HgError::unsupported("bundle repository").into())
             } else {
                 Err(RepoError::NotFound {
                     at: root.to_owned(),
                 })
             }
         } else {
             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 Self::new_at_path(ancestor.to_owned(), config);
                 }
             }
             Err(RepoError::NotFound {
                 at: current_directory,
             })
         }
     }
 
     /// 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_newlines()).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()
                 ))
                 .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)",
                     ),
                     _ => 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)",
                         ),
                         _ => 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,
         };
 
         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
-
-    // The undescore prefix silences the "never used" warning. Remove before
-    // using.
-    pub fn _working_directory_vfs(&self) -> Vfs<'_> {
+    pub fn working_directory_vfs(&self) -> Vfs<'_> {
         Vfs {
             base: &self.working_directory,
         }
     }
 
     pub fn dirstate_parents(
         &self,
     ) -> Result<crate::dirstate::DirstateParents, HgError> {
         let dirstate = self.hg_vfs().mmap_open("dirstate")?;
         let parents =
             crate::dirstate::parsers::parse_dirstate_parents(&dirstate)?;
         Ok(parents.clone())
     }
 }
 
 impl Vfs<'_> {
     pub fn join(&self, relative_path: impl AsRef<Path>) -> PathBuf {
         self.base.join(relative_path)
     }
 
     pub fn read(
         &self,
         relative_path: impl AsRef<Path>,
     ) -> Result<Vec<u8>, HgError> {
         let path = self.join(relative_path);
         std::fs::read(&path).when_reading_file(&path)
     }
 
     pub 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).when_reading_file(&path)?;
         // TODO: what are the safety requirements here?
         let mmap = unsafe { MmapOptions::new().map(&file) }
             .when_reading_file(&path)?;
         Ok(mmap)
     }
 
     pub fn rename(
         &self,
         relative_from: impl AsRef<Path>,
         relative_to: impl AsRef<Path>,
     ) -> Result<(), HgError> {
         let from = self.join(relative_from);
         let to = self.join(relative_to);
         std::fs::rename(&from, &to)
             .with_context(|| IoErrorContext::RenamingFile { from, to })
     }
 }

rust/rhg/src/main.rs

@@ -1,507 +1,509 b''
 extern crate log;
 use crate::ui::Ui;
 use clap::App;
 use clap::AppSettings;
 use clap::Arg;
 use clap::ArgMatches;
 use format_bytes::{format_bytes, join};
 use hg::config::Config;
 use hg::repo::{Repo, RepoError};
 use hg::utils::files::{get_bytes_from_os_str, get_path_from_bytes};
 use hg::utils::SliceExt;
 use std::ffi::OsString;
 use std::path::PathBuf;
 use std::process::Command;
 
 mod blackbox;
 mod error;
 mod exitcode;
 mod ui;
 use error::CommandError;
 
 fn main_with_result(
     process_start_time: &blackbox::ProcessStartTime,
     ui: &ui::Ui,
     repo: Result<&Repo, &NoRepoInCwdError>,
     config: &Config,
 ) -> Result<(), CommandError> {
     check_extensions(config)?;
 
     let app = App::new("rhg")
         .global_setting(AppSettings::AllowInvalidUtf8)
         .global_setting(AppSettings::DisableVersion)
         .setting(AppSettings::SubcommandRequired)
         .setting(AppSettings::VersionlessSubcommands)
         .arg(
             Arg::with_name("repository")
                 .help("repository root directory")
                 .short("-R")
                 .long("--repository")
                 .value_name("REPO")
                 .takes_value(true)
                 // Both ok: `hg -R ./foo log` or `hg log -R ./foo`
                 .global(true),
         )
         .arg(
             Arg::with_name("config")
                 .help("set/override config option (use 'section.name=value')")
                 .long("--config")
                 .value_name("CONFIG")
                 .takes_value(true)
                 .global(true)
                 // Ok: `--config section.key1=val --config section.key2=val2`
                 .multiple(true)
                 // Not ok: `--config section.key1=val section.key2=val2`
                 .number_of_values(1),
         )
         .arg(
             Arg::with_name("cwd")
                 .help("change working directory")
                 .long("--cwd")
                 .value_name("DIR")
                 .takes_value(true)
                 .global(true),
         )
         .version("0.0.1");
     let app = add_subcommand_args(app);
 
     let matches = app.clone().get_matches_safe()?;
 
     let (subcommand_name, subcommand_matches) = matches.subcommand();
     let run = subcommand_run_fn(subcommand_name)
         .expect("unknown subcommand name from clap despite AppSettings::SubcommandRequired");
     let subcommand_args = subcommand_matches
         .expect("no subcommand arguments from clap despite AppSettings::SubcommandRequired");
 
     let invocation = CliInvocation {
         ui,
         subcommand_args,
         config,
         repo,
     };
     let blackbox = blackbox::Blackbox::new(&invocation, process_start_time)?;
     blackbox.log_command_start();
     let result = run(&invocation);
     blackbox.log_command_end(exit_code(
         &result,
         // TODO: show a warning or combine with original error if `get_bool`
         // returns an error
         config
             .get_bool(b"ui", b"detailed-exit-code")
             .unwrap_or(false),
     ));
     result
 }
 
 fn main() {
     // Run this first, before we find out if the blackbox extension is even
     // enabled, in order to include everything in-between in the duration
     // measurements. Reading config files can be slow if they’re on NFS.
     let process_start_time = blackbox::ProcessStartTime::now();
 
     env_logger::init();
     let ui = ui::Ui::new();
 
     let early_args = EarlyArgs::parse(std::env::args_os());
 
     let initial_current_dir = early_args.cwd.map(|cwd| {
         let cwd = get_path_from_bytes(&cwd);
         std::env::current_dir()
             .and_then(|initial| {
                 std::env::set_current_dir(cwd)?;
                 Ok(initial)
             })
             .unwrap_or_else(|error| {
                 exit(
                     &None,
                     &ui,
                     OnUnsupported::Abort,
                     Err(CommandError::abort(format!(
                         "abort: {}: '{}'",
                         error,
                         cwd.display()
                     ))),
                     false,
                 )
             })
     });
 
     let non_repo_config =
         Config::load(early_args.config).unwrap_or_else(|error| {
             // Normally this is decided based on config, but we don’t have that
             // available. As of this writing config loading never returns an
             // "unsupported" error but that is not enforced by the type system.
             let on_unsupported = OnUnsupported::Abort;
 
             exit(
                 &initial_current_dir,
                 &ui,
                 on_unsupported,
                 Err(error.into()),
                 false,
             )
         });
 
     if let Some(repo_path_bytes) = &early_args.repo {
         lazy_static::lazy_static! {
             static ref SCHEME_RE: regex::bytes::Regex =
                 // Same as `_matchscheme` in `mercurial/util.py`
                 regex::bytes::Regex::new("^[a-zA-Z0-9+.\\-]+:").unwrap();
         }
         if SCHEME_RE.is_match(&repo_path_bytes) {
             exit(
                 &initial_current_dir,
                 &ui,
                 OnUnsupported::from_config(&ui, &non_repo_config),
                 Err(CommandError::UnsupportedFeature {
                     message: format_bytes!(
                         b"URL-like --repository {}",
                         repo_path_bytes
                     ),
                 }),
                 // TODO: show a warning or combine with original error if
                 // `get_bool` returns an error
                 non_repo_config
                     .get_bool(b"ui", b"detailed-exit-code")
                     .unwrap_or(false),
             )
         }
     }
     let repo_path = early_args.repo.as_deref().map(get_path_from_bytes);
     let repo_result = match Repo::find(&non_repo_config, repo_path) {
         Ok(repo) => Ok(repo),
         Err(RepoError::NotFound { at }) if repo_path.is_none() => {
             // Not finding a repo is not fatal yet, if `-R` was not given
             Err(NoRepoInCwdError { cwd: at })
         }
         Err(error) => exit(
             &initial_current_dir,
             &ui,
             OnUnsupported::from_config(&ui, &non_repo_config),
             Err(error.into()),
             // TODO: show a warning or combine with original error if
             // `get_bool` returns an error
             non_repo_config
                 .get_bool(b"ui", b"detailed-exit-code")
                 .unwrap_or(false),
         ),
     };
 
     let config = if let Ok(repo) = &repo_result {
         repo.config()
     } else {
         &non_repo_config
     };
     let on_unsupported = OnUnsupported::from_config(&ui, config);
 
     let result = main_with_result(
         &process_start_time,
         &ui,
         repo_result.as_ref(),
         config,
     );
     exit(
         &initial_current_dir,
         &ui,
         on_unsupported,
         result,
         // TODO: show a warning or combine with original error if `get_bool`
         // returns an error
         config
             .get_bool(b"ui", b"detailed-exit-code")
             .unwrap_or(false),
     )
 }
 
 fn exit_code(
     result: &Result<(), CommandError>,
     use_detailed_exit_code: bool,
 ) -> i32 {
     match result {
         Ok(()) => exitcode::OK,
         Err(CommandError::Abort {
             message: _,
             detailed_exit_code,
         }) => {
             if use_detailed_exit_code {
                 *detailed_exit_code
             } else {
                 exitcode::ABORT
             }
         }
         Err(CommandError::Unsuccessful) => exitcode::UNSUCCESSFUL,
 
         // Exit with a specific code and no error message to let a potential
         // wrapper script fallback to Python-based Mercurial.
         Err(CommandError::UnsupportedFeature { .. }) => {
             exitcode::UNIMPLEMENTED
         }
     }
 }
 
 fn exit(
     initial_current_dir: &Option<PathBuf>,
     ui: &Ui,
     mut on_unsupported: OnUnsupported,
     result: Result<(), CommandError>,
     use_detailed_exit_code: bool,
 ) -> ! {
     if let (
         OnUnsupported::Fallback { executable },
         Err(CommandError::UnsupportedFeature { .. }),
     ) = (&on_unsupported, &result)
     {
         let mut args = std::env::args_os();
         let executable_path = get_path_from_bytes(&executable);
         let this_executable = args.next().expect("exepcted argv[0] to exist");
         if executable_path == &PathBuf::from(this_executable) {
             // Avoid spawning infinitely many processes until resource
             // exhaustion.
             let _ = ui.write_stderr(&format_bytes!(
                 b"Blocking recursive fallback. The 'rhg.fallback-executable = {}' config \
                 points to `rhg` itself.\n",
                 executable
             ));
             on_unsupported = OnUnsupported::Abort
         } else {
             // `args` is now `argv[1..]` since we’ve already consumed `argv[0]`
             let mut command = Command::new(executable_path);
             command.args(args);
             if let Some(initial) = initial_current_dir {
                 command.current_dir(initial);
             }
             let result = command.status();
             match result {
                 Ok(status) => std::process::exit(
                     status.code().unwrap_or(exitcode::ABORT),
                 ),
                 Err(error) => {
                     let _ = ui.write_stderr(&format_bytes!(
                         b"tried to fall back to a '{}' sub-process but got error {}\n",
                         executable, format_bytes::Utf8(error)
                     ));
                     on_unsupported = OnUnsupported::Abort
                 }
             }
         }
     }
     exit_no_fallback(ui, on_unsupported, result, use_detailed_exit_code)
 }
 
 fn exit_no_fallback(
     ui: &Ui,
     on_unsupported: OnUnsupported,
     result: Result<(), CommandError>,
     use_detailed_exit_code: bool,
 ) -> ! {
     match &result {
         Ok(_) => {}
         Err(CommandError::Unsuccessful) => {}
         Err(CommandError::Abort {
             message,
             detailed_exit_code: _,
         }) => {
             if !message.is_empty() {
                 // Ignore errors when writing to stderr, we’re already exiting
                 // with failure code so there’s not much more we can do.
                 let _ = ui.write_stderr(&format_bytes!(b"{}\n", message));
             }
         }
         Err(CommandError::UnsupportedFeature { message }) => {
             match on_unsupported {
                 OnUnsupported::Abort => {
                     let _ = ui.write_stderr(&format_bytes!(
                         b"unsupported feature: {}\n",
                         message
                     ));
                 }
                 OnUnsupported::AbortSilent => {}
                 OnUnsupported::Fallback { .. } => unreachable!(),
             }
         }
     }
     std::process::exit(exit_code(&result, use_detailed_exit_code))
 }
 
 macro_rules! subcommands {
     ($( $command: ident )+) => {
         mod commands {
             $(
                 pub mod $command;
             )+
         }
 
         fn add_subcommand_args<'a, 'b>(app: App<'a, 'b>) -> App<'a, 'b> {
             app
             $(
                 .subcommand(commands::$command::args())
             )+
         }
 
         pub type RunFn = fn(&CliInvocation) -> Result<(), CommandError>;
 
         fn subcommand_run_fn(name: &str) -> Option<RunFn> {
             match name {
                 $(
                     stringify!($command) => Some(commands::$command::run),
                 )+
                 _ => None,
             }
         }
     };
 }
 
 subcommands! {
     cat
     debugdata
     debugrequirements
     files
     root
     config
+    status
 }
+
 pub struct CliInvocation<'a> {
     ui: &'a Ui,
     subcommand_args: &'a ArgMatches<'a>,
     config: &'a Config,
     /// References inside `Result` is a bit peculiar but allow
     /// `invocation.repo?` to work out with `&CliInvocation` since this
     /// `Result` type is `Copy`.
     repo: Result<&'a Repo, &'a NoRepoInCwdError>,
 }
 
 struct NoRepoInCwdError {
     cwd: PathBuf,
 }
 
 /// CLI arguments to be parsed "early" in order to be able to read
 /// configuration before using Clap. Ideally we would also use Clap for this,
 /// see <https://github.com/clap-rs/clap/discussions/2366>.
 ///
 /// These arguments are still declared when we do use Clap later, so that Clap
 /// does not return an error for their presence.
 struct EarlyArgs {
     /// Values of all `--config` arguments. (Possibly none)
     config: Vec<Vec<u8>>,
     /// Value of the `-R` or `--repository` argument, if any.
     repo: Option<Vec<u8>>,
     /// Value of the `--cwd` argument, if any.
     cwd: Option<Vec<u8>>,
 }
 
 impl EarlyArgs {
     fn parse(args: impl IntoIterator<Item = OsString>) -> Self {
         let mut args = args.into_iter().map(get_bytes_from_os_str);
         let mut config = Vec::new();
         let mut repo = None;
         let mut cwd = None;
         // Use `while let` instead of `for` so that we can also call
         // `args.next()` inside the loop.
         while let Some(arg) = args.next() {
             if arg == b"--config" {
                 if let Some(value) = args.next() {
                     config.push(value)
                 }
             } else if let Some(value) = arg.drop_prefix(b"--config=") {
                 config.push(value.to_owned())
             }
 
             if arg == b"--cwd" {
                 if let Some(value) = args.next() {
                     cwd = Some(value)
                 }
             } else if let Some(value) = arg.drop_prefix(b"--cwd=") {
                 cwd = Some(value.to_owned())
             }
 
             if arg == b"--repository" || arg == b"-R" {
                 if let Some(value) = args.next() {
                     repo = Some(value)
                 }
             } else if let Some(value) = arg.drop_prefix(b"--repository=") {
                 repo = Some(value.to_owned())
             } else if let Some(value) = arg.drop_prefix(b"-R") {
                 repo = Some(value.to_owned())
             }
         }
         Self { config, repo, cwd }
     }
 }
 
 /// What to do when encountering some unsupported feature.
 ///
 /// See `HgError::UnsupportedFeature` and `CommandError::UnsupportedFeature`.
 enum OnUnsupported {
     /// Print an error message describing what feature is not supported,
     /// and exit with code 252.
     Abort,
     /// Silently exit with code 252.
     AbortSilent,
     /// Try running a Python implementation
     Fallback { executable: Vec<u8> },
 }
 
 impl OnUnsupported {
     const DEFAULT: Self = OnUnsupported::Abort;
 
     fn from_config(ui: &Ui, config: &Config) -> Self {
         match config
             .get(b"rhg", b"on-unsupported")
             .map(|value| value.to_ascii_lowercase())
             .as_deref()
         {
             Some(b"abort") => OnUnsupported::Abort,
             Some(b"abort-silent") => OnUnsupported::AbortSilent,
             Some(b"fallback") => OnUnsupported::Fallback {
                 executable: config
                     .get(b"rhg", b"fallback-executable")
                     .unwrap_or_else(|| {
                         exit_no_fallback(
                             ui,
                             Self::Abort,
                             Err(CommandError::abort(
                                 "abort: 'rhg.on-unsupported=fallback' without \
                                 'rhg.fallback-executable' set."
                             )),
                             false,
                         )
                     })
                     .to_owned(),
             },
             None => Self::DEFAULT,
             Some(_) => {
                 // TODO: warn about unknown config value
                 Self::DEFAULT
             }
         }
     }
 }
 
 const SUPPORTED_EXTENSIONS: &[&[u8]] = &[b"blackbox", b"share"];
 
 fn check_extensions(config: &Config) -> Result<(), CommandError> {
     let enabled = config.get_section_keys(b"extensions");
 
     let mut unsupported = enabled;
     for supported in SUPPORTED_EXTENSIONS {
         unsupported.remove(supported);
     }
 
     if let Some(ignored_list) =
         config.get_simple_list(b"rhg", b"ignored-extensions")
     {
         for ignored in ignored_list {
             unsupported.remove(ignored);
         }
     }
 
     if unsupported.is_empty() {
         Ok(())
     } else {
         Err(CommandError::UnsupportedFeature {
             message: format_bytes!(
                 b"extensions: {} (consider adding them to 'rhg.ignored-extensions' config)",
                 join(unsupported, b", ")
             ),
         })
     }
 }