semora-cli 1.1.0

//! `.semora`: marks a folder as a Semora project, and where a push came from.
//!
//! The file is TOML meant to be committed:
//!
//! ```toml
//! server = "3f9c0e7a5b1d4e2f8a6c9b0d1e2f3a4b"
//! project = "semora"
//! ```
//!
//! `server` is the id the server gave itself, so the file does not say where the server is.
//! It is only compared with the id of the configured server, never used to reach one: a cloned
//! repository must not be able to send your API key to another host. A file from before ids
//! holds the server's URL; one for the configured server is moved to the id on first use.

use std::path::{Component, Path, PathBuf};

use anyhow::{Context, bail};
use serde::Deserialize;

use crate::client::Client;
use crate::config::{origin, parse_server};
use crate::local_links::{self, LocalLink};
use crate::{checkout, exit, output, server_id};

pub const FILE: &str = ".semora";

/// A path for messages: without the `\\?\` prefix that `canonicalize` adds on Windows.
pub fn shown(path: &Path) -> String {
    let s = path.display().to_string();
    match s.strip_prefix(r"\\?\") {
        Some(rest) => match rest.strip_prefix(r"UNC\") {
            Some(share) => format!(r"\\{share}"),
            None => rest.to_string(),
        },
        None => s,
    }
}

/// A `.semora` names another server than the one this command uses. Commands add their own
/// way out (push: `--id` or `--new`).
#[derive(Debug)]
pub struct OtherServer(pub String);

impl std::fmt::Display for OtherServer {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.0)
    }
}

impl std::error::Error for OtherServer {}

/// What a `.semora` names its server by.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum ServerRef {
    /// The server's id, trimmed and lowercase.
    Id(String),
    /// A URL from before ids, as an origin.
    Url(String),
}

/// A `.semora` as it is written, before the CLI has asked its server whether the file is for it.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct FileLink {
    /// The folder that holds `.semora` (canonical).
    pub root: PathBuf,
    pub server: ServerRef,
    pub slug: String,
}

/// A `.semora` that is for the server this command uses.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Link {
    /// The folder that holds `.semora` (canonical).
    pub root: PathBuf,
    /// The origin of the server this command uses.
    pub server: String,
    /// The project id the commands use.
    pub slug: String,
    /// The project id `.semora` names.
    pub file_slug: String,
    /// Set when the file is used for this server through a record on this machine
    /// (`semora project link`), not because it names this server. A new project id then goes in
    /// the record, never in the shared file.
    pub local: Option<Mapped>,
}

/// The record a link is used through, and the config folder that holds it.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Mapped {
    pub config_dir: PathBuf,
    pub record: LocalLink,
}

impl Link {
    pub fn mapped(&self) -> bool {
        self.local.is_some()
    }
}

/// How a `.semora` relates to the server this command uses.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Fit {
    /// It names this server's id.
    Ours,
    /// It names this server by URL, from before ids.
    LegacyOurs,
    /// It names another server by URL, this origin.
    LegacyOther(String),
    /// It names another server's id.
    Other,
    /// It names another server, and a record on this machine uses it with this one.
    Mapped(LocalLink),
}

/// The `server` value of a file as local records key it.
pub fn server_value(server: &ServerRef) -> String {
    match server {
        ServerRef::Id(id) | ServerRef::Url(id) => id.clone(),
    }
}

#[derive(Deserialize)]
struct Raw {
    server: Option<String>,
    project: Option<String>,
}

/// `[a-z0-9-]`, 1 to 40 characters, not starting with a dash.
pub fn valid_slug(s: &str) -> bool {
    (1..=40).contains(&s.len())
        && s.bytes()
            .all(|b| b.is_ascii_lowercase() || b.is_ascii_digit() || b == b'-')
        && !s.starts_with('-')
}

/// A project id from a directory name: lowercase it, turn every run of other characters into
/// one `-`, trim `-` from both ends, cut to 40 characters, trim again.
pub fn slug_from(dir_name: &str) -> Option<String> {
    let mut out = String::new();
    for c in dir_name.to_lowercase().chars() {
        if c.is_ascii_lowercase() || c.is_ascii_digit() {
            out.push(c);
        } else if !out.ends_with('-') {
            out.push('-');
        }
    }
    let cut: String = out.trim_matches('-').chars().take(40).collect();
    let slug = cut.trim_matches('-').to_string();
    valid_slug(&slug).then_some(slug)
}

/// The `.semora` in `dir` itself, if there is one.
pub fn read_at(dir: &Path) -> anyhow::Result<Option<FileLink>> {
    let file = dir.join(FILE);
    if !file.is_file() {
        return Ok(None);
    }
    let text =
        std::fs::read_to_string(&file).with_context(|| format!("reading {}", shown(&file)))?;
    let raw: Raw = toml::from_str(&text).with_context(|| format!("parsing {}", shown(&file)))?;
    let server = raw
        .server
        .filter(|s| !s.trim().is_empty())
        .with_context(|| format!("{} needs a `server` line", shown(&file)))?;
    let slug = raw
        .project
        .filter(|s| !s.trim().is_empty())
        .with_context(|| format!("{} needs a `project` line", shown(&file)))?;
    if !valid_slug(&slug) {
        bail!(
            "{}: `{slug}` is not a valid project id (lowercase letters, digits and dashes, up to 40, starting with a letter or digit)",
            shown(&file)
        );
    }
    let server = if server_id::is_id(&server) {
        ServerRef::Id(server_id::normal(&server))
    } else {
        let url =
            parse_server(&server).with_context(|| format!("{}: bad `server`", shown(&file)))?;
        ServerRef::Url(origin(&url))
    };
    Ok(Some(FileLink {
        root: dir.to_path_buf(),
        server,
        slug,
    }))
}

/// The folder to start looking from: the path's folder, or the path itself for a folder.
fn start_dir(full: &Path) -> Option<&Path> {
    if full.is_dir() {
        Some(full)
    } else {
        full.parent()
    }
}

/// Looks for `.semora` in the path's folder and each parent. The nearest file wins. The
/// current directory plays no part. `Err` means a file was found but is unusable.
pub fn find(path: &Path) -> anyhow::Result<Option<FileLink>> {
    let full =
        std::fs::canonicalize(path).with_context(|| format!("cannot read {}", shown(path)))?;
    let mut dir = start_dir(&full);
    while let Some(d) = dir {
        if let Some(link) = read_at(d)? {
            return Ok(Some(link));
        }
        dir = d.parent();
    }
    Ok(None)
}

/// Writes `dir/.semora` naming the server by its id. Returns its path.
pub fn write(dir: &Path, server_id: &str, slug: &str) -> anyhow::Result<PathBuf> {
    let file = dir.join(FILE);
    let text = format!(
        "# Semora project. Commit this file so every checkout publishes to the same place.\nserver = \"{server_id}\"\nproject = \"{slug}\"\n"
    );
    std::fs::write(&file, text).with_context(|| format!("writing {}", shown(&file)))?;
    Ok(file)
}

/// Sets the `key` line (`project` or `server`) of `dir/.semora` to `value`, keeping every other
/// line as it is.
pub fn set_line(dir: &Path, key: &str, value: &str) -> anyhow::Result<()> {
    let file = dir.join(FILE);
    let text =
        std::fs::read_to_string(&file).with_context(|| format!("reading {}", shown(&file)))?;
    let eol = if text.contains("\r\n") { "\r\n" } else { "\n" };
    let mut found = false;
    let mut lines: Vec<String> = Vec::new();
    for line in text.lines() {
        let is_key = line
            .trim_start()
            .strip_prefix(key)
            .is_some_and(|rest| rest.trim_start().starts_with('='));
        if is_key && !found {
            found = true;
            lines.push(format!("{key} = \"{value}\""));
        } else {
            lines.push(line.to_string());
        }
    }
    if !found {
        bail!("{} has no `{key}` line to update", shown(&file));
    }
    let new_text = lines.join(eol) + eol;
    std::fs::write(&file, &new_text).with_context(|| format!("writing {}", shown(&file)))?;
    // The line must have said what we meant; if not, put the file back.
    let meant = |l: &FileLink| match key {
        "project" => l.slug == value,
        _ => l.server == ServerRef::Id(value.to_string()),
    };
    match read_at(dir) {
        Ok(Some(l)) if meant(&l) => Ok(()),
        _ => {
            std::fs::write(&file, &text).ok();
            bail!("could not update the `{key}` line in {}", shown(&file))
        }
    }
}

/// The project has the id `slug` on the server now. Rewrites `.semora` (or, for a link used
/// through a record on this machine, the record) and the checkout record to it and says so. Any
/// other answer leaves the link as it is.
pub fn adopt(link: Link, slug: &str) -> Link {
    if slug == link.slug || !valid_slug(slug) {
        return link;
    }
    if let Some(m) = &link.local {
        let record = LocalLink {
            project: slug.to_string(),
            ..m.record.clone()
        };
        if let Err(e) = local_links::save(&m.config_dir, record.clone()) {
            output::warn(format!(
                "project `{}` is now `{slug}` on {}, but this machine's link could not be updated: {e:#}. Run `semora project link --project {slug}`.",
                link.slug, link.server
            ));
            return link;
        }
        let moved = Link {
            slug: slug.to_string(),
            local: Some(Mapped {
                config_dir: m.config_dir.clone(),
                record,
            }),
            ..link.clone()
        };
        if let Err(e) = checkout::move_to(&link, &moved) {
            output::warn(format!(
                "could not carry this folder's record over to the new id: {e:#}. Run `semora pull` to start it again."
            ));
        }
        output::warn(format!(
            "project '{}' is now '{slug}' on {}. Updated this machine's link.",
            link.slug, link.server
        ));
        return moved;
    }
    if let Err(e) = set_line(&link.root, "project", slug) {
        output::warn(format!(
            "project `{}` is now `{slug}` on {}, but {e:#}. Change the `project` line yourself.",
            link.slug, link.server
        ));
        return link;
    }
    let moved = Link {
        slug: slug.to_string(),
        file_slug: slug.to_string(),
        ..link.clone()
    };
    if let Err(e) = checkout::move_to(&link, &moved) {
        output::warn(format!(
            "could not carry this folder's record over to the new id: {e:#}. Run `semora pull` to start it again."
        ));
    }
    output::warn(format!(
        "project `{}` is now `{slug}` on {}. Updated {}; commit it so other checkouts follow.",
        link.slug,
        link.server,
        shown(&link.root.join(FILE))
    ));
    moved
}

/// The project as the server knows it now. An owner can give a project a new id; while the old
/// one is an alias the server answers it with the new one. When the old id is gone, a document
/// this folder pulled or pushed still says which project it is in. Errors other than a missing
/// project are left for the command itself to report.
pub async fn follow(client: &Client, link: Link) -> anyhow::Result<Link> {
    let link = match client.project(&link.slug).await {
        Ok(info) => adopt(link, &info.slug),
        Err(e) if exit::is_not_found(&e) => recover(client, link).await,
        Err(_) => link,
    };
    keep_record(client, &link).await;
    Ok(link)
}

/// Another checkout followed the project to a new id and the new `.semora` came in with git,
/// so this folder's record is still under the old id. When a document in it is in this
/// project now, the record is kept under the new id; without it, pushes could no longer tell
/// a stale copy, and pull could no longer tell local changes from the server's.
async fn keep_record(client: &Client, link: &Link) {
    for id in checkout::ids_under_other_id(link)
        .into_iter()
        .take(RECOVER_TRIES)
    {
        let Ok(d) = client.doc(&id).await else {
            continue;
        };
        if d.summary.project.as_deref() == Some(link.slug.as_str())
            && let Err(e) = checkout::relabel(link)
        {
            output::warn(format!(
                "could not carry this folder's record over to project `{}`: {e:#}",
                link.slug
            ));
        }
        // The first document still there decides: in another project, the record is not ours.
        return;
    }
}

/// How many recorded documents to ask about before giving up.
const RECOVER_TRIES: usize = 3;

/// The old id is unknown to the server. Asks for documents this folder recorded and takes the
/// project the first one that is still there is in.
async fn recover(client: &Client, link: Link) -> Link {
    let Ok(records) = checkout::load(&link) else {
        return link;
    };
    let mut ids: Vec<String> = records.into_values().map(|r| r.id).collect();
    ids.dedup();
    for id in ids.into_iter().take(RECOVER_TRIES) {
        if let Ok(d) = client.doc(&id).await
            && let Some(project) = d.summary.project
        {
            return adopt(link, &project);
        }
    }
    link
}

/// How `file` relates to the server `client` uses. An id that differs from the cached one is
/// checked once more with the server, in case the address now leads to another server. A file
/// for another server may still be used here through a record on this machine.
pub async fn fit(client: &Client, config_dir: &Path, file: &FileLink) -> anyhow::Result<Fit> {
    let ours = match &file.server {
        ServerRef::Id(id) => {
            *id == server_id::of(client, config_dir, false).await?
                || *id == server_id::of(client, config_dir, true).await?
        }
        ServerRef::Url(u) if *u == client.origin() => return Ok(Fit::LegacyOurs),
        ServerRef::Url(_) => false,
    };
    if ours {
        return Ok(Fit::Ours);
    }
    if let Some(record) = local_links::find(config_dir, &server_value(&file.server), &file.slug)? {
        let id = server_id::of(client, config_dir, false).await?;
        if record.server_id == id
            || record.server_id == server_id::of(client, config_dir, true).await?
        {
            return Ok(Fit::Mapped(record));
        }
    }
    Ok(match &file.server {
        ServerRef::Url(u) => Fit::LegacyOther(u.clone()),
        ServerRef::Id(_) => Fit::Other,
    })
}

/// `file` as a link for the server `client` uses, or the error that says why it is not and what
/// to do. Nothing is sent for the project before this answers.
pub async fn resolve(client: &Client, config_dir: &Path, file: FileLink) -> anyhow::Result<Link> {
    let path = shown(&file.root.join(FILE));
    let have = client.origin();
    let mut local = None;
    let mut slug = file.slug.clone();
    match fit(client, config_dir, &file).await? {
        Fit::Ours => drop_shadowed(client, config_dir, &file, &path).await,
        Fit::LegacyOurs => {
            // The id goes into a committed file, so it is asked for, not taken from the cache.
            let id = server_id::of(client, config_dir, true).await?;
            match set_line(&file.root, "server", &id) {
                Ok(()) => output::warn(format!(
                    "{path} now names its server by id instead of address. Commit it. Older commits still hold the address."
                )),
                Err(e) => output::warn(format!(
                    "could not update {path}: {e:#}. Change the `server` line to \"{id}\" yourself."
                )),
            }
        }
        Fit::Mapped(record) => {
            slug = record.project.clone();
            local = Some(Mapped {
                config_dir: config_dir.to_path_buf(),
                record,
            });
        }
        Fit::LegacyOther(theirs) => {
            return Err(OtherServer(format!(
                "{path} is for {theirs}, but this command uses {have}. To use that server, set SEMORA_URL or pass --server {theirs}."
            ))
            .into());
        }
        Fit::Other => return Err(OtherServer(other_server_message(&path, &have)).into()),
    }
    Ok(Link {
        root: file.root,
        server: have,
        slug,
        file_slug: file.slug,
        local,
    })
}

/// The file names this server now, so records on this machine that sent its project here from
/// another server are no longer used. They are dropped; one that used another project id is
/// worth a word, since the file's id is used from now on.
async fn drop_shadowed(client: &Client, config_dir: &Path, file: &FileLink, path: &str) {
    let Ok(id) = server_id::of(client, config_dir, false).await else {
        return;
    };
    match local_links::remove_shadowed(config_dir, &id, &file.slug, &file.root) {
        Ok(gone) => {
            for g in gone.iter().filter(|g| g.project != file.slug) {
                output::warn(format!(
                    "{path} now names this server, so this machine's link to project '{}' is dropped; the file's project '{}' is used.",
                    g.project, file.slug
                ));
            }
        }
        Err(e) => output::warn(format!("{e:#}")),
    }
}

/// The file names another server's id. It can't say which server that is, so the message names
/// only this one and the ways out.
fn other_server_message(path: &str, have: &str) -> String {
    format!(
        "{path} is for another Semora server than the one this CLI uses ({have}).
The file does not say which server it is. Either:
  - log in to the project's server: semora login --server ADDRESS (ask whoever set up the project)
  - use your server for this project on this machine only: semora project link
    (your documents drift from everyone else's; nobody else sees them)
  - point .semora at your server: semora project link --rewrite
    (once you commit it, every other checkout stops working until it does the same)"
    )
}

impl Link {
    /// The pushed path relative to the project root, joined with `/`.
    pub fn relative_path(&self, target: &Path) -> anyhow::Result<String> {
        let full = std::fs::canonicalize(target)
            .with_context(|| format!("cannot read {}", shown(target)))?;
        let rel = full.strip_prefix(&self.root).with_context(|| {
            format!(
                "{} is not inside the project at {}",
                shown(&full),
                shown(&self.root)
            )
        })?;
        let mut parts = Vec::new();
        for c in rel.components() {
            let s = c.as_os_str().to_str().with_context(|| {
                format!(
                    "{} isn't valid Unicode, so it can't be a project path",
                    shown(&full)
                )
            })?;
            parts.push(s.to_string());
        }
        if parts.is_empty() {
            bail!(
                "{} is here: push a file or a folder inside this project, not the project root.",
                shown(&self.root.join(FILE))
            );
        }
        Ok(parts.join("/"))
    }
}

/// The branch of the git checkout the path is in, read from `HEAD` (no `git` process).
/// A worktree's `.git` is a file that names its git folder; a relative name is relative to
/// the folder that holds that file. The walk starts from `std::path::absolute`, not
/// `canonicalize`: on Windows a canonical path is a `\\?\` path, and those do not resolve `..`
/// or `/`, so the relative name is joined and cleaned up lexically instead.
pub fn git_branch(path: &Path) -> Option<String> {
    let full = std::path::absolute(path).ok()?;
    let mut dir = start_dir(&full);
    while let Some(d) = dir {
        let dot = d.join(".git");
        if dot.is_dir() {
            return branch_in(&dot);
        }
        if dot.is_file() {
            let text = std::fs::read_to_string(&dot).ok()?;
            let target = text
                .lines()
                .find_map(|l| l.trim().strip_prefix("gitdir:"))?
                .trim();
            let gitdir = if Path::new(target).is_absolute() {
                PathBuf::from(target)
            } else {
                lexical(&d.join(target))
            };
            return branch_in(&gitdir);
        }
        dir = d.parent();
    }
    None
}

/// `.` and `..` resolved without touching the file system.
fn lexical(path: &Path) -> PathBuf {
    let mut out = PathBuf::new();
    for c in path.components() {
        match c {
            Component::CurDir => {}
            Component::ParentDir => {
                if !out.pop() {
                    out.push("..");
                }
            }
            other => out.push(other.as_os_str()),
        }
    }
    out
}

fn branch_in(gitdir: &Path) -> Option<String> {
    let head = std::fs::read_to_string(gitdir.join("HEAD")).ok()?;
    head.trim()
        .strip_prefix("ref: refs/heads/")
        .map(str::to_string)
        .filter(|b| !b.is_empty())
}

/// Where a push came from: `machine · branch`, or just the machine.
pub fn origin_for(path: &Path) -> String {
    let machine = crate::commands::login::hostname();
    match git_branch(path) {
        Some(b) => format!("{machine} \u{b7} {b}"),
        None => machine,
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn dir() -> tempfile::TempDir {
        tempfile::tempdir().unwrap()
    }

    /// The link a command gets for a file that is for its server.
    fn linked(f: FileLink) -> Link {
        Link {
            root: f.root,
            server: "https://a.example.com".into(),
            slug: f.slug.clone(),
            file_slug: f.slug,
            local: None,
        }
    }

    fn put(root: &Path, rel: &str, text: &str) -> PathBuf {
        let p = root.join(rel);
        std::fs::create_dir_all(p.parent().unwrap()).unwrap();
        std::fs::write(&p, text).unwrap();
        p
    }

    #[test]
    fn slugs_follow_the_rule() {
        let (x40, x41) = ("x".repeat(40), "x".repeat(41));
        for ok in ["semora", "a", "9-a", x40.as_str()] {
            assert!(valid_slug(ok), "{ok}");
        }
        for bad in ["", "Semora", "-x", "a b", x41.as_str()] {
            assert!(!valid_slug(bad), "{bad}");
        }
    }

    #[test]
    fn a_slug_is_made_from_a_directory_name() {
        assert_eq!(slug_from("My Docs_v2").as_deref(), Some("my-docs-v2"));
        assert_eq!(slug_from(".tmpAbC123").as_deref(), Some("tmpabc123"));
        assert_eq!(slug_from("--a--b--").as_deref(), Some("a-b"));
        assert_eq!(slug_from("semora").as_deref(), Some("semora"));
        assert_eq!(slug_from(&"a".repeat(50)).unwrap().len(), 40);
        let a39 = "a".repeat(39);
        assert_eq!(
            slug_from(&format!("{a39}-b")).as_deref(),
            Some(a39.as_str()),
            "no dash left at the cut"
        );
        assert_eq!(slug_from("___"), None);
        assert_eq!(slug_from(""), None);
    }

    #[test]
    fn dot_semora_is_parsed_and_checked() {
        let d = dir();
        put(
            d.path(),
            ".semora",
            "# note\nserver = \"https://Semora.example.com/\"\nproject = \"semora\"\nextra = 1\n",
        );
        let link = read_at(d.path()).unwrap().unwrap();
        assert_eq!(link.slug, "semora");
        assert_eq!(
            link.server,
            ServerRef::Url("https://semora.example.com".into()),
            "the origin, whatever the spelling"
        );
        put(
            d.path(),
            ".semora",
            "server = \" 3F9C0E7A5B1D4E2F8A6C9B0D1E2F3A4B \"\nproject = \"semora\"\n",
        );
        assert_eq!(
            read_at(d.path()).unwrap().unwrap().server,
            ServerRef::Id("3f9c0e7a5b1d4e2f8a6c9b0d1e2f3a4b".into()),
            "an id, normalized"
        );

        for (text, why) in [
            ("project = \"x\"\n", "server"),
            ("server = \"https://a.example.com\"\n", "project"),
            (
                "server = \"https://a.example.com\"\nproject = \"Bad Id\"\n",
                "valid project id",
            ),
            ("server = \n", "parsing"),
        ] {
            put(d.path(), ".semora", text);
            let err = read_at(d.path()).unwrap_err().to_string();
            assert!(
                err.contains(why) && err.contains(".semora"),
                "{text:?} -> {err}"
            );
        }
        std::fs::remove_file(d.path().join(".semora")).unwrap();
        assert_eq!(read_at(d.path()).unwrap(), None);
    }

    #[test]
    fn find_walks_up_from_the_path_and_the_nearest_file_wins() {
        let d = dir();
        put(
            d.path(),
            ".semora",
            "server = \"https://a.example.com\"\nproject = \"outer\"\n",
        );
        put(
            d.path(),
            "inner/.semora",
            "server = \"https://a.example.com\"\nproject = \"inner\"\n",
        );
        let file = put(d.path(), "docs/deep/x.md", "# x");
        put(d.path(), "inner/y.md", "# y");
        assert_eq!(find(&file).unwrap().unwrap().slug, "outer");
        assert_eq!(
            find(&d.path().join("docs")).unwrap().unwrap().slug,
            "outer",
            "a folder"
        );
        assert_eq!(
            find(&d.path().join("inner/y.md")).unwrap().unwrap().slug,
            "inner"
        );
        assert_eq!(
            find(&d.path().join("inner")).unwrap().unwrap().slug,
            "inner",
            "the folder's own file"
        );
        let lonely = tempfile::tempdir().unwrap();
        let f = put(lonely.path(), "z.md", "# z");
        assert_eq!(find(&f).unwrap(), None);
    }

    #[test]
    fn the_key_path_is_relative_with_forward_slashes() {
        let d = dir();
        put(
            d.path(),
            ".semora",
            "server = \"https://a.example.com\"\nproject = \"p\"\n",
        );
        let file = put(d.path(), "docs/deep/x.md", "# x");
        let link = linked(find(&file).unwrap().unwrap());
        assert_eq!(link.relative_path(&file).unwrap(), "docs/deep/x.md");
        assert_eq!(link.relative_path(&d.path().join("docs")).unwrap(), "docs");
        let err = link.relative_path(d.path()).unwrap_err().to_string();
        assert!(err.contains("not the project root"), "{err}");
    }

    #[test]
    fn the_message_for_another_servers_id_names_only_this_one_and_the_ways_out() {
        let m = other_server_message("/r/.semora", "https://mine.example.com");
        for part in [
            "/r/.semora",
            "https://mine.example.com",
            "semora login --server ADDRESS",
            "semora project link",
            "semora project link --rewrite",
        ] {
            assert!(m.contains(part), "{part}: {m}");
        }
        assert!(
            !m.contains("--id") && !m.contains("--new"),
            "push flags are push's to mention, not every command's: {m}"
        );
    }

    #[test]
    fn write_makes_a_file_that_reads_back() {
        let d = dir();
        let id = "3f9c0e7a5b1d4e2f8a6c9b0d1e2f3a4b";
        let path = write(d.path(), id, "semora").unwrap();
        let text = std::fs::read_to_string(&path).unwrap();
        assert!(text.starts_with("# Semora project."), "{text}");
        let link = read_at(d.path()).unwrap().unwrap();
        assert_eq!(
            (link.server, link.slug.as_str()),
            (ServerRef::Id(id.into()), "semora")
        );
    }

    #[test]
    fn paths_in_messages_lose_the_windows_verbatim_prefix() {
        assert_eq!(
            shown(Path::new(r"\\?\C:\Development\x\.semora")),
            r"C:\Development\x\.semora"
        );
        assert_eq!(shown(Path::new(r"\\?\UNC\nas\share\x")), r"\\nas\share\x");
        assert_eq!(shown(Path::new("/home/a/x")), "/home/a/x");
    }

    #[test]
    fn dots_are_resolved_without_the_file_system() {
        assert_eq!(lexical(Path::new("/a/b/../c/./d")), PathBuf::from("/a/c/d"));
        assert_eq!(lexical(Path::new("a/../../b")), PathBuf::from("../b"));
    }

    #[test]
    fn the_branch_comes_from_head() {
        let d = dir();
        put(d.path(), ".git/HEAD", "ref: refs/heads/feat/projects\n");
        let file = put(d.path(), "docs/x.md", "# x");
        assert_eq!(git_branch(&file).as_deref(), Some("feat/projects"));
        put(
            d.path(),
            ".git/HEAD",
            "0123456789abcdef0123456789abcdef01234567\n",
        );
        assert_eq!(git_branch(&file), None, "a detached HEAD has no branch");
    }

    #[test]
    fn a_worktree_points_at_its_git_folder_absolute_or_relative() {
        let d = dir();
        let main = put(
            d.path(),
            "main/.git/worktrees/wt/HEAD",
            "ref: refs/heads/feat/wt\n",
        );
        let abs = main.parent().unwrap().to_string_lossy().replace('\\', "/");
        put(d.path(), "abs/.git", &format!("gitdir: {abs}\n"));
        let file = put(d.path(), "abs/x.md", "# x");
        assert_eq!(
            git_branch(&file).as_deref(),
            Some("feat/wt"),
            "absolute gitdir"
        );
        // Relative to the folder that holds the `.git` file, not to the current directory.
        put(d.path(), "rel/.git", "gitdir: ../main/.git/worktrees/wt\n");
        let file = put(d.path(), "rel/x.md", "# x");
        assert_eq!(
            git_branch(&file).as_deref(),
            Some("feat/wt"),
            "relative gitdir"
        );
    }

    #[test]
    fn a_verbatim_path_still_reads_a_relative_gitdir() {
        // `watch` passes a canonical path; on Windows that is a `\\?\` path, where `/` is not a
        // separator, so a relative `gitdir` must not be joined onto it as it is.
        let d = dir();
        put(
            d.path(),
            "main/.git/worktrees/wt/HEAD",
            "ref: refs/heads/feat/wt\n",
        );
        put(d.path(), "rel/.git", "gitdir: ../main/.git/worktrees/wt\n");
        let file = put(d.path(), "rel/x.md", "# x");
        let canonical = std::fs::canonicalize(&file).unwrap();
        if cfg!(windows) {
            assert!(
                canonical.to_string_lossy().starts_with(r"\\?\"),
                "{canonical:?}"
            );
        }
        assert_eq!(git_branch(&canonical).as_deref(), Some("feat/wt"));
    }

    #[test]
    fn origin_is_the_machine_and_the_branch_when_there_is_one() {
        let d = dir();
        let file = put(d.path(), "x.md", "# x");
        let machine = origin_for(&file);
        assert!(!machine.contains('\u{b7}'), "no branch: {machine}");
        put(d.path(), ".git/HEAD", "ref: refs/heads/main\n");
        let with = origin_for(&file);
        assert_eq!(with, format!("{machine} \u{b7} main"));
    }
}