fix(tui): gate color on the CLI entry point, not cfg!(test)

[jd]

colors_enabled() opened with if cfg!(test) { return false }, whose
comment claims tests "never depend on the dev's TTY". It cannot do
that: cfg!(test) is false whenever mergify-tui is compiled as a
dependency, so the guard only ever covered mergify-tui's own tests.
Every consumer crate's tests fell through to the real policy and read
the developer's environment — FORCE_COLOR=1 cargo test -p mergify-events fails on main today, on escape sequences injected into
asserted output.

Gate on the recorded --color choice instead. set_color_choice() is
called from exactly one place, detect_dispatch() in main, so an unset
choice means the process did not come through the CLI: a test harness,
a doctest, an embedder. Colors stay off there, in any environment,
across every crate.

resolve_enabled() takes the Option<ColorChoice> so the new case is
covered by the existing precedence unit test rather than by global
state.

Refs MRGFY-8533.

[jd]

This pull request is part of a Mergify stack:

#	Pull Request	Link
1	fix(tui): gate color on the CLI entry point, not cfg!(test)	#1765	👈
2	feat(events): make the default page fast and readable	#1766

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[Copilot]

Pull request overview

This PR fixes color-detection in mergify-tui by removing an ineffective cfg!(test) gate (which only applied to mergify-tui’s own unit tests) and instead disabling colors unless the CLI entry point explicitly records a --color preference via set_color_choice().

Changes:

• Make color enablement depend on whether set_color_choice() has been called (i.e., whether execution came through the CLI entry point).
• Refactor resolve_enabled to accept Option<ColorChoice> so the “no recorded choice” case is explicitly modeled and unit-tested.
• Update documentation/comments and expand unit test coverage for the new precedence behavior.

Suppressed comments (1)

crates/mergify-tui/src/theme.rs:165

• colors_enabled() already treats an unset COLOR_CHOICE as “colors off”, but it still reads NO_COLOR/FORCE_COLOR and probes stdout().is_terminal() even though those values can’t affect the result when choice is None. Returning early when the choice is unset better matches the stated policy (“must not take a dependency on the developer's terminal or environment”) and avoids unnecessary syscalls in test/embedded contexts.

pub(crate) fn colors_enabled() -> bool {
    // An unset choice means we are not the CLI: colors off. This
    // used to be `cfg!(test)`, which cannot do the job — it is false
    // whenever this crate is compiled as a dependency, so every
    // *consumer* crate's tests were reading the developer's
    // environment after all. `FORCE_COLOR=1 cargo test` failed on the
    // escape sequences that leaked into asserted output.
    let choice = COLOR_CHOICE.get().copied();
    let no_color = std::env::var_os("NO_COLOR").is_some();
    let force_color =
        std::env::var_os("FORCE_COLOR").is_some() || std::env::var_os("CLICOLOR_FORCE").is_some();
    resolve_enabled(
        choice,
        no_color,
        force_color,
        std::io::stdout().is_terminal(),
    )

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[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-08-10 12:23 UTC · Rule: default · triggered by merge protections
• ✅ Checks passed · on draft merge queue: checking main (cc0c6ba) and #1765 together #1768
• ✅ Merged — 2026-08-10 12:30 UTC · at 678b9256b72a78835ef180c8f07b54820f872fe2 · squash

This pull request spent 6 minutes 39 seconds in the queue, including 6 minutes 16 seconds running CI.

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