amont_runtime/

config.rs

//! Reading configuration — and reading it the way git itself does.
//!
//! Everything this project can be tuned with is a `git config` key, so the
//! honest implementation of that promise is to let git do the parsing.
//! `git config --type=bool` implements git-config(1) by definition: `on`,
//! `yes`, `1`, an empty value, and every capitalisation of each. A hand-rolled
//! `matches!(v, "true" | "1" | "yes")` is our own dialect wearing git's
//! clothes, and it had already drifted — `git config amont.fix on` looked
//! like it worked and did not.
//!
//! The exit code carries the part that matters most:
//!
//! | exit | means |
//! |---|---|
//! | 0 | the key is set, and stdout is git's normalised value |
//! | 1 | the key is not set anywhere git looked |
//! | 128 | the key is set to something git refuses to parse, and said so on stderr |
//!
//! Collapsing 1 and 128 into "no" is the bug this module exists to prevent: a
//! limit you believe you raised and did not is exactly the silent-config
//! failure that `hook.skip` announcements were introduced for. So a bad value
//! falls back to the shipped default **and says so**, once per key per run.

use crate::git;
use crate::ui::{highlight, warning_sign};
use std::collections::BTreeSet;
use std::ops::RangeInclusive;
use std::sync::{Mutex, OnceLock};

/// What a key said. Three answers, because "unset" is a state this project
/// makes decisions with — `amont.commit.gitmoji` has four meanings and one
/// of them is absence.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Value<T> {
    Unset,
    Set(T),
    /// Set to something that could not be read. `why` is git's own diagnostic
    /// where git produced one, and ours where the constraint is ours (a value
    /// outside an allowed set, or outside a range).
    Bad {
        why: String,
    },
}

impl<T> Value<T> {
    pub fn is_set(&self) -> bool {
        matches!(self, Value::Set(_))
    }
}

/// `git config --type=<ty> --get <key>`, with the three exits kept apart.
///
/// Git failing to run at all is reported as `Unset`: this crate's standing
/// posture is that an unanswerable question takes the default rather than
/// blocking a commit.
fn typed(key: &str, ty: &str) -> Value<String> {
    let type_flag = format!("--type={ty}");
    let Some(out) = git::output(&["config", &type_flag, "--get", key]) else {
        return Value::Unset;
    };
    match out.code {
        0 => Value::Set(out.stdout),
        1 => Value::Unset,
        _ => Value::Bad {
            why: first_line(&out.stderr),
        },
    }
}

/// As [`typed`], but reading a POLICY-SUPPLIED literal instead of the
/// machine's config: `git -c <key>=<raw> config --type=<ty> --get <key>`.
/// GIT parses the value, so `Value::Bad` and `complain` work unchanged and
/// no second config dialect exists — the founding argument of this module.
fn typed_literal(key: &str, raw: &str, ty: Option<&str>) -> Value<String> {
    let assignment = format!("{key}={raw}");
    let mut args: Vec<&str> = vec!["-c", &assignment, "config"];
    let type_flag = ty.map(|t| format!("--type={t}"));
    if let Some(tf) = &type_flag {
        args.push(tf);
    }
    args.extend(["--get", key]);
    let Some(out) = git::output(&args) else {
        return Value::Unset;
    };
    match out.code {
        0 => Value::Set(out.stdout),
        1 => Value::Unset,
        _ => Value::Bad {
            why: first_line(&out.stderr),
        },
    }
}

/// The ladder, as a short-circuit rather than a general mechanism:
///
///   policy has no value for `key`      → [`typed`], byte-for-byte as before
///   key set at local/worktree/command  → [`typed`] — the machine wins
///   otherwise                          → [`typed_literal`] — policy wins
///
/// The invariant this shape buys: a repository with no `set` lines spawns
/// not one extra git process anywhere — the scoped scan below runs only
/// when the policy actually carries settings.
fn resolve(settings: &crate::config::Settings, key: &str, ty: Option<&str>) -> Value<String> {
    let policy = settings.policy();
    let Some(raw) = policy.settings.get(key) else {
        return match ty {
            Some(t) => typed(key, t),
            None => untyped(key),
        };
    };
    if key_set_above_policy(settings, key) {
        return match ty {
            Some(t) => typed(key, t),
            None => untyped(key),
        };
    }
    typed_literal(key, raw, ty)
}

/// The raw read `enumerated` has always done, factored so `resolve` can
/// route it.
fn untyped(key: &str) -> Value<String> {
    let Some(out) = git::output(&["config", "--get", key]) else {
        return Value::Unset;
    };
    match out.code {
        0 => Value::Set(out.stdout),
        1 => Value::Unset,
        _ => Value::Bad {
            why: first_line(&out.stderr),
        },
    }
}

/// Is `key` set at a scope that outranks policy (local/worktree/command)?
///
/// One lazily-cached `git config --show-scope --get-regexp '^amont\.'` for
/// the whole process — this is the PRECEDENCE reader, deliberately separate
/// from [`scope_of`], which is `--show-origin`-based and display-oriented.
/// Scope words `system`/`global` rank below policy; every other word —
/// `local`, `worktree`, `command`, and whatever a future git invents —
/// ranks above, because misreading a local as below would let a file pulled
/// from a remote silently override a person's explicit machine setting.
///
/// On a git too old for `--show-scope` the cache is `None` and this
/// DEGRADES fail-safe: any set key counts as above, i.e. all git config
/// beats policy.
fn key_set_above_policy(settings: &crate::config::Settings, key: &str) -> bool {
    let above = settings.scoped.get_or_init(|| {
        crate::git::stdout(&["config", "--show-scope", "--get-regexp", r"^amont\."]).map(|scoped| {
            scoped
                .lines()
                .filter_map(|line| {
                    let (scope, rest) = line.split_once('\t')?;
                    match scope {
                        "system" | "global" => None,
                        _ => rest.split_whitespace().next().map(str::to_ascii_lowercase),
                    }
                })
                .collect()
        })
    });
    match above {
        Some(set) => set.contains(&key.to_ascii_lowercase()),
        // Degraded: no scope information — any set key beats policy.
        None => untyped(key).is_set(),
    }
}

/// Git's `fatal:` line, without the noise around it. Empty stderr still yields
/// something printable, because a warning that names no cause is a puzzle.
fn first_line(stderr: &str) -> String {
    let line = stderr.lines().next().unwrap_or("").trim();
    let line = line.strip_prefix("fatal: ").unwrap_or(line);
    if line.is_empty() {
        "git could not read the value".to_string()
    } else {
        line.to_string()
    }
}

/// Everything this process resolved once about configuration: the trusted
/// repository policy, and the reads memoised on top of it.
///
/// This replaces a process-global `OnceLock<Policy>`. The global was correct
/// for the hook path — one process means one repository — but it made a rule
/// the compiler could not see. A multi-repo walker had to KNOW not to seed
/// it, and `amont-fleet` carried that knowledge as a comment with no test
/// able to assert it, because asserting it would have meant seeding it.
///
/// Owned high and borrowed everywhere — the shape `Ctx` already uses for
/// `manifest` and `push` — the rule stops needing to be remembered: there is
/// no store to seed. The memo fields keep the per-process caching these reads
/// have always had, which `spawn_budget` measures; one `Settings` per process
/// buys the same number of git spawns the statics did.
#[derive(Debug, Default)]
pub struct Settings {
    policy: crate::policy::Policy,
    /// The precedence reader: one `--show-scope` scan per process.
    scoped: OnceLock<Option<BTreeSet<String>>>,
    /// The host-key reader: one `--show-scope` scan with values, run only
    /// when a host key is first read. `(scope, key lowercased, value)`.
    host: OnceLock<Option<Vec<(String, String, String)>>>,
    /// Reads memoised on first use. Each was a module-level `OnceLock` beside
    /// its accessor; here, "resolved once" is scoped to a `Settings` rather
    /// than to the process, so a second one cannot inherit the first's answers.
    pub(crate) timeout: OnceLock<u64>,
    pub(crate) idle: OnceLock<u64>,
    pub(crate) idle_cpu: OnceLock<bool>,
    pub(crate) lock_wait: OnceLock<u64>,
    pub(crate) idle_load_scale: OnceLock<u64>,
    pub(crate) quiet: OnceLock<bool>,
    pub(crate) progress: OnceLock<bool>,
    pub(crate) declared_mode: OnceLock<bool>,
    pub(crate) fixing: OnceLock<bool>,
}

/// `amont run --quiet` or `--raw`.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum QuietOverride {
    Quiet,
    Raw,
}

impl Settings {
    /// Decide `amont.quiet` for this run, ahead of the configuration:
    /// `amont run --quiet` / `--raw`. Only before anything has read it —
    /// a read first would have fixed the answer, and the flag would do
    /// nothing; that is a bug in the caller, not a configuration.
    pub fn override_quiet(&self, mode: QuietOverride) {
        let quiet = match mode {
            QuietOverride::Quiet => true,
            QuietOverride::Raw => false,
        };
        self.quiet
            .set(quiet)
            .expect("amont.quiet was read before --quiet/--raw could decide it");
    }

    /// The policy a trusted manifest declared — empty when nothing was
    /// declared or the manifest was not trusted. `manifest::load` decides
    /// that and hands the answer here.
    pub fn new(policy: crate::policy::Policy) -> Self {
        Self {
            policy,
            ..Self::default()
        }
    }

    pub fn policy(&self) -> &crate::policy::Policy {
        &self.policy
    }

    /// A fresh `Settings` over the same policy, with empty caches.
    ///
    /// For a spawned thread, which cannot borrow this one. It resolves the
    /// same answers — same policy, same git config — and it resolves them
    /// LAZILY, which is the property that matters: a paint or heartbeat
    /// thread that never lives long enough to read a budget must not have
    /// cost a `git config` spawn for it up front. Handing the thread
    /// pre-resolved numbers did exactly that, and `spawn_budget` said so.
    pub fn for_thread(&self) -> Settings {
        Settings::new(self.policy.clone())
    }
}

pub fn boolean(settings: &crate::config::Settings, key: &str) -> Value<bool> {
    match resolve(settings, key, Some("bool")) {
        Value::Set(v) => match v.as_str() {
            "true" => Value::Set(true),
            "false" => Value::Set(false),
            other => Value::Bad {
                why: format!("git normalised it to {other:?}, which is neither true nor false"),
            },
        },
        Value::Unset => Value::Unset,
        Value::Bad { why } => Value::Bad { why },
    }
}

/// An integer, in git's own spelling — which includes the `k`/`m`/`g` suffixes
/// git accepts, since `--type=int` expands them before we see them.
pub fn integer(settings: &crate::config::Settings, key: &str) -> Value<i64> {
    match resolve(settings, key, Some("int")) {
        Value::Set(v) => match v.parse::<i64>() {
            Ok(n) => Value::Set(n),
            Err(_) => Value::Bad {
                why: format!("git returned {v:?}, which is not a whole number"),
            },
        },
        Value::Unset => Value::Unset,
        Value::Bad { why } => Value::Bad { why },
    }
}

/// One of a fixed set of words, compared case-insensitively.
///
/// Git has no `--type` for this, so the value is read raw and checked here —
/// which means this is the one reader whose `Bad` message is ours. It names
/// every accepted spelling, because a rejection that does not say what was
/// wanted sends the reader to the documentation for a list we already hold.
pub fn enumerated(
    settings: &crate::config::Settings,
    key: &str,
    allowed: &[&'static str],
) -> Value<&'static str> {
    match resolve(settings, key, None) {
        Value::Set(v) => {
            let got = v.trim().to_ascii_lowercase();
            match allowed.iter().find(|a| a.eq_ignore_ascii_case(&got)) {
                Some(hit) => Value::Set(hit),
                None => Value::Bad {
                    why: format!("{got:?} is not one of {}", allowed.join(", ")),
                },
            }
        }
        Value::Unset => Value::Unset,
        Value::Bad { why } => Value::Bad { why },
    }
}

/// Say once, per key, that a configured value could not be used.
///
/// Deduplicated because a key read twice in one run is a detail of how the
/// code is arranged, and repeating the warning would make it look like two
/// separate mistakes.
/// A free-form string key, policy-aware. Untyped reads have no `--type`
/// for git to refuse, so `Bad` cannot arise — this is Set-or-not.
pub fn string_value(settings: &crate::config::Settings, key: &str) -> Option<String> {
    match resolve(settings, key, None) {
        Value::Set(v) => Some(v),
        _ => None,
    }
}

pub fn complain(key: &str, why: &str, using: &str) {
    static SAID: OnceLock<Mutex<BTreeSet<String>>> = OnceLock::new();
    let said = SAID.get_or_init(|| Mutex::new(BTreeSet::new()));
    // A poisoned mutex means another thread panicked mid-insert; warning twice
    // is strictly better than joining it in panicking.
    let fresh = match said.lock() {
        Ok(mut set) => set.insert(key.to_string()),
        Err(_) => true,
    };
    if fresh {
        eprintln!(
            "{} {}: {why} — using {using}",
            warning_sign().trim(),
            highlight(key)
        );
    }
}

pub fn boolean_or(settings: &crate::config::Settings, key: &str, default: bool) -> bool {
    match boolean(settings, key) {
        Value::Set(v) => v,
        Value::Unset => default,
        Value::Bad { why } => {
            complain(key, &why, &default.to_string());
            default
        }
    }
}

/// An integer, clamped to what the setting can actually mean.
///
/// Out of range is treated exactly as unparseable: a `subjectMax` of 0 would
/// block every commit forever from a config file, and one of 10_000 is not a
/// limit. Both are mistakes, and both get the default plus a line saying so.
pub fn integer_or(
    settings: &crate::config::Settings,
    key: &str,
    default: i64,
    range: RangeInclusive<i64>,
) -> i64 {
    match integer(settings, key) {
        Value::Set(v) if range.contains(&v) => v,
        Value::Set(v) => {
            complain(
                key,
                &format!("{v} is outside {}..={}", range.start(), range.end()),
                &default.to_string(),
            );
            default
        }
        Value::Unset => default,
        Value::Bad { why } => {
            complain(key, &why, &default.to_string());
            default
        }
    }
}

/// A HOST key: a setting that describes the machine — how many heavy checks
/// it runs at once, how far its load may stretch a budget — and so is read
/// from `--global` or `--system` config only (ADR-0009). A value set in a
/// repository is ignored with one warning naming the scope to use: two
/// repositories that disagreed about the host's slot count would each take
/// slots the other never sees. An environment variable named after the key
/// (`amont.idleLoadScale` → `AMONT_IDLE_LOAD_SCALE`) outranks both, which
/// is the precedence `cli.config.precedence` gives it: flag or environment,
/// then the person's config, then the system's, then the default. The
/// `amont.conf` policy ladder does not apply: a committed file cannot set
/// a host key.
///
/// One `--show-scope` scan per `Settings`, run on the first host key read
/// and never before: `amont.idleLoadScale` is read when the first observed
/// tool of any check is spawned, so a commit that runs no tool spawns
/// nothing for it and one that does pays exactly one spawn, pinned by
/// `spawn_budget.rs`.
pub fn host_integer_or(
    settings: &crate::config::Settings,
    key: &str,
    default: i64,
    range: RangeInclusive<i64>,
) -> i64 {
    let accept = |raw: &str, source: &str| -> Option<i64> {
        match raw.trim().parse::<i64>() {
            Ok(v) if range.contains(&v) => Some(v),
            Ok(v) => {
                complain(
                    key,
                    &format!(
                        "{v} ({source}) is outside {}..={}",
                        range.start(),
                        range.end()
                    ),
                    &default.to_string(),
                );
                None
            }
            Err(_) => {
                complain(
                    key,
                    &format!("{raw:?} ({source}) is not a whole number"),
                    &default.to_string(),
                );
                None
            }
        }
    };
    let env_name = host_env_name(key);
    if let Some(raw) = std::env::var(&env_name)
        .ok()
        .filter(|v| !v.trim().is_empty())
    {
        if let Some(v) = accept(&raw, &env_name) {
            return v;
        }
    }
    let rows = settings.host.get_or_init(|| {
        git::stdout(&["config", "--show-scope", "--get-regexp", r"^amont\."]).map(|out| {
            out.lines()
                .filter_map(|line| {
                    let (scope, rest) = line.split_once('\t')?;
                    let (k, v) = match rest.split_once(' ') {
                        Some((k, v)) => (k, v),
                        None => (rest, ""),
                    };
                    Some((scope.to_string(), k.to_ascii_lowercase(), v.to_string()))
                })
                .collect()
        })
    });
    let Some(rows) = rows else {
        // A git too old for `--show-scope`: the default, said once.
        complain(key, "git cannot report config scopes", &default.to_string());
        return default;
    };
    let wanted = key.to_ascii_lowercase();
    let host = rows
        .iter()
        .rev()
        .find(|(scope, k, _)| *k == wanted && (scope == "global" || scope == "system"));
    if host.is_none() && rows.iter().any(|(_, k, _)| *k == wanted) {
        complain(
            key,
            "is set in this repository's config, but a host key is read from --global or \
             --system only",
            &default.to_string(),
        );
    }
    host.and_then(|(scope, _, v)| accept(v, scope))
        .unwrap_or(default)
}

/// `amont.idleLoadScale` → `AMONT_IDLE_LOAD_SCALE`: the environment name a
/// host key answers to.
pub fn host_env_name(key: &str) -> String {
    let mut out = String::from("AMONT");
    for part in key.trim_start_matches("amont.").split('.') {
        out.push('_');
        for c in part.chars() {
            if c.is_ascii_uppercase() {
                out.push('_');
            }
            out.push(c.to_ascii_uppercase());
        }
    }
    out
}

#[cfg(test)]
mod host_key_tests {
    #[test]
    fn a_host_key_names_its_environment_variable() {
        use super::host_env_name;
        assert_eq!(
            host_env_name("amont.idleLoadScale"),
            "AMONT_IDLE_LOAD_SCALE"
        );
        assert_eq!(host_env_name("amont.hostSlots"), "AMONT_HOST_SLOTS");
        assert_eq!(host_env_name("amont.timeout"), "AMONT_TIMEOUT");
        assert_eq!(
            host_env_name("amont.commit.bodyWrap"),
            "AMONT_COMMIT_BODY_WRAP"
        );
    }
}

pub fn enumerated_or(
    settings: &crate::config::Settings,
    key: &str,
    allowed: &[&'static str],
    default: &'static str,
) -> &'static str {
    match enumerated(settings, key, allowed) {
        Value::Set(v) => v,
        Value::Unset => default,
        Value::Bad { why } => {
            complain(key, &why, default);
            default
        }
    }
}

/// Which keys under `prefix` are set at all — one git call for the whole
/// family.
///
/// This runs on the commit path, where four independent `--get` calls would be
/// four processes spent discovering that nobody has configured anything. One
/// `--get-regexp` answers that, and only the keys it names are read for real.
/// Same shape as `registry::Overrides::read`, for the same reason.
///
/// **Names come back lowercased.** Git lowercases the section and key parts of
/// every name it prints, so `amont.commit.subjectMax` is reported as
/// `amont.commit.subjectmax`. Keys are case-insensitive on lookup, so this
/// only affects comparison here — hence [`is_present`] rather than a bare
/// `contains`.
pub fn present(settings: &crate::config::Settings, prefix: &str) -> BTreeSet<String> {
    let pattern = format!("^{}", regex_escape(prefix));
    let policy_names = || -> BTreeSet<String> {
        settings
            .policy()
            .settings
            .keys()
            .filter(|k| {
                k.to_ascii_lowercase()
                    .starts_with(&prefix.to_ascii_lowercase())
            })
            .map(|k| k.to_ascii_lowercase())
            .collect()
    };
    let Some(out) = git::output(&["config", "--get-regexp", &pattern]) else {
        return policy_names();
    };
    if out.code != 0 {
        return policy_names();
    }
    let mut names: BTreeSet<String> = out
        .stdout
        .lines()
        .filter_map(|l| l.split_whitespace().next())
        .map(|k| k.to_ascii_lowercase())
        .collect();
    names.extend(
        settings
            .policy()
            .settings
            .keys()
            .filter(|k| {
                k.to_ascii_lowercase()
                    .starts_with(&prefix.to_ascii_lowercase())
            })
            .map(|k| k.to_ascii_lowercase()),
    );
    names
}

/// Is `key` among the names [`present`] returned? Case-insensitive, because
/// git config key names are.
pub fn is_present(names: &BTreeSet<String>, key: &str) -> bool {
    names.contains(&key.to_ascii_lowercase())
}

/// Escape the characters a config key can hold that a POSIX basic regex would
/// otherwise read as syntax. Only `.` occurs in practice; the rest are here so
/// this cannot become wrong if a caller passes something else.
fn regex_escape(s: &str) -> String {
    let mut out = String::with_capacity(s.len() * 2);
    for c in s.chars() {
        if matches!(c, '.' | '*' | '[' | ']' | '^' | '$' | '\\') {
            out.push('\\');
        }
        out.push(c);
    }
    out
}

/// Where a key's value came from, for the commands whose job is reading
/// configuration back.
///
/// This costs a second git call per key and must never be used on the commit
/// path — `amont list` and `amont setup` are the only callers, and they
/// are already asking git several questions to render one screen.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Scope {
    Default,
    Local,
    Global,
    System,
    CommandLine,
    /// The value in effect comes from the repository's committed policy.
    Policy,
    Other,
}

impl Scope {
    pub fn as_str(self) -> &'static str {
        match self {
            Scope::Default => "default",
            Scope::Local => "local",
            Scope::Global => "global",
            Scope::System => "system",
            Scope::CommandLine => "command line",
            Scope::Policy => "amont.conf",
            Scope::Other => "other",
        }
    }
}

/// `git config --show-origin --get <key>` → which file it came from.
///
/// `Default` for a key nobody set, which is also the answer when git cannot be
/// asked — the value in use is the shipped one either way.
pub fn scope_of(settings: &crate::config::Settings, key: &str) -> Scope {
    // Display mirrors resolution: policy owns the key unless something above
    // it on the ladder set it. The precedence answer comes from the same
    // classifier `resolve` uses, never re-derived from file paths.
    if settings.policy().settings.contains_key(key) && !key_set_above_policy(settings, key) {
        return Scope::Policy;
    }
    let Some(out) = git::output(&["config", "--show-origin", "--get", key]) else {
        return Scope::Default;
    };
    if out.code != 0 {
        return Scope::Default;
    }
    // `<origin>\t<value>`; the origin is `file:/path`, `command line:` or
    // `blob:…`, and the path is what tells local from global.
    let origin = out.stdout.split('\t').next().unwrap_or("");
    if origin.starts_with("command line") {
        return Scope::CommandLine;
    }
    let Some(path) = origin.strip_prefix("file:") else {
        return Scope::Other;
    };
    let path = path.trim();
    // A repository's own config is the only one inside a `.git` directory;
    // asking git for the paths rather than guessing at `~` keeps this correct
    // under `GIT_CONFIG_GLOBAL`, worktrees and `$XDG_CONFIG_HOME`.
    if same_file(
        path,
        git::stdout(&["rev-parse", "--git-path", "config"]).as_deref(),
    ) {
        return Scope::Local;
    }
    for (flag, scope) in [("--global", Scope::Global), ("--system", Scope::System)] {
        let listed = git::output(&["config", flag, "--list", "--show-origin"]);
        if let Some(o) = listed {
            if o.code == 0
                && o.stdout
                    .lines()
                    .filter_map(|l| l.split('\t').next())
                    .filter_map(|o| o.strip_prefix("file:"))
                    .any(|p| same_file(path, Some(p.trim())))
            {
                return scope;
            }
        }
    }
    Scope::Other
}

/// Compare two paths as the same file where the filesystem can say so, falling
/// back to the strings. `--git-path` answers relatively (`.git/config`) while
/// `--show-origin` may answer absolutely, so a string comparison alone
/// misreports a local key as `other`.
fn same_file(a: &str, b: Option<&str>) -> bool {
    let Some(b) = b else { return false };
    if a == b {
        return true;
    }
    match (std::fs::canonicalize(a), std::fs::canonicalize(b)) {
        (Ok(x), Ok(y)) => x == y,
        _ => false,
    }
}

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

    /// The distinction the whole module exists for: git's two failure exits
    /// mean opposite things, and `first_line` is what a reader is shown for
    /// the one that is a mistake.
    #[test]
    fn a_fatal_line_is_reported_without_its_prefix() {
        assert_eq!(
            first_line("fatal: bad numeric config value 'wide' for 'a.b'"),
            "bad numeric config value 'wide' for 'a.b'"
        );
        assert_eq!(first_line("first\nsecond"), "first");
    }

    /// A warning that names no cause is a puzzle, so there is always a cause.
    #[test]
    fn an_empty_diagnostic_still_says_something() {
        assert!(!first_line("").is_empty());
        assert!(!first_line("   \n  ").is_empty());
    }

    #[test]
    fn a_key_name_is_escaped_before_it_becomes_a_pattern() {
        // Without escaping, `.` matches any character and the prefix would
        // also select `amontXcommit.*`.
        assert_eq!(regex_escape("amont.commit."), "amont\\.commit\\.");
        assert_eq!(regex_escape("plain"), "plain");
    }

    /// Git lowercases the names it prints, so a presence test that respected
    /// case would answer "not set" for every camelCase key we ship.
    #[test]
    fn presence_is_case_insensitive_because_git_lowercases_names() {
        let names: BTreeSet<String> = ["amont.commit.subjectmax".to_string()]
            .into_iter()
            .collect();
        assert!(is_present(&names, "amont.commit.subjectMax"));
        assert!(is_present(&names, "AMONT.COMMIT.SUBJECTMAX"));
        assert!(!is_present(&names, "amont.commit.bodyWrap"));
    }

    #[test]
    fn every_scope_has_a_name() {
        for s in [
            Scope::Default,
            Scope::Local,
            Scope::Global,
            Scope::System,
            Scope::CommandLine,
            Scope::Other,
        ] {
            assert!(!s.as_str().is_empty());
        }
    }
}