feat(stack): fzf-style interactive picker for mergify stack open

[kozlek]

What

mergify stack open with no <commit> argument on a terminal now shows an fzf-style fuzzy picker over the stack's PRs — type to filter (skim's SkimMatcherV2 via dialoguer::FuzzySelect), matched characters highlighted, leaf (HEAD) preselected, Enter opens the PR in the browser.

The Python CLI had an interactive picker; the Rust port dropped it ("left out of the port for now"). This restores it, upgraded from an arrow-key list to fuzzy filtering.

Behavior

Invocation	Behavior
mergify stack open (stdin+stdout+stderr all TTYs)	fuzzy picker, HEAD preselected
Esc in picker	prints nothing, exit 0
Ctrl-C in picker	exit 130 (fzf convention), cursor restored
mergify stack open non-TTY	unchanged: silently opens leaf PR
mergify stack open <commit>	unchanged: opens that commit's PR, no picker
empty stack	unchanged: "No commits in stack", exit 3

Entries without a PR are listed as (no PR) <title> (<sha7>) so the stack shape stays visible; selecting one fails with the existing "run mergify stack push first" error.

Design notes

• dialoguer stays behind a new mergify_tui::select::fuzzy_select() boundary — command crates never depend on it, and future pickers (checkout, edit, reword) reuse the same entry point. Dep is dialoguer 0.12, default-features = false, features = ["fuzzy-select"].
• open::Options gains an injectable Selector callback (same testability-by-parameter pattern as queue pause's confirm), so cancel/label logic is unit-tested without a TTY.
• Ctrl-C: console re-raises SIGINT from its raw-mode key reader, which would kill the process with dialoguer's hidden cursor leaked. A lazily-installed ctrlc handler restores the cursor and exits 130. (console is pinned to the same 0.16 dialoguer uses; single copy in the lockfile.)
• TTY gate includes stderr because dialoguer renders the list on stderr — without it, mergify stack open 2>/dev/null would sit in raw mode drawing nothing.
• The commit argument's clap doc was updated; the CLI-schema golden snapshot regenerated (that one description only).

Test plan

• Unit tests: cancel contract (Interrupted → cancel fallback), label building, leaf-default index, selector error mapping (19 new/updated tests; workspace suite green)
• Non-TTY smoke: piped stdin keeps the non-interactive path, no hang
• Manual TTY check: picker/filter/Enter, Esc → $? = 0, Ctrl-C → $? = 130 with cursor visible, 2>/dev/null opens leaf silently

🤖 Generated with Claude Code

[mergify]

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[Copilot]

Pull request overview

Adds an interactive, fzf-style fuzzy picker to mergify stack open when no <commit> is provided and all stdio streams are TTYs, while preserving the existing non-interactive “open leaf PR” behavior for scripts/pipes. The picker implementation is introduced behind a new mergify-tui boundary and wired into stack open via an injectable selector callback for testability.

Changes:

• Introduces mergify_tui::select::fuzzy_select() (dialoguer FuzzySelect) with match highlighting and cancellation mapping.
• Extends mergify stack open to optionally run an injected selector (TTY-gated in the binary) and adds a Cancelled outcome.
• Updates CLI schema snapshot/help text and adds new dependencies (dialoguer, ctrlc, console) in the workspace.

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
crates/mergify-tui/src/theme.rs	Exposes colors_enabled() to allow picker theming to follow the existing color policy.
crates/mergify-tui/src/select.rs	New fuzzy-picker wrapper around dialoguer, including SIGINT/cursor-restore logic.
crates/mergify-tui/src/lib.rs	Exports the new select module and fuzzy_select() API.
crates/mergify-tui/Cargo.toml	Adds dialoguer, ctrlc, and console dependencies for picker functionality.
crates/mergify-stack/src/commands/open.rs	Adds selector injection, label building, interactive selection, and Cancelled outcome.
crates/mergify-cli/src/snapshots/mergify__tests__cli_schema_golden.snap	Updates the stack open commit help/longHelp text in the schema snapshot.
crates/mergify-cli/src/main.rs	Wires TTY gating and injects mergify_tui::fuzzy_select into stack open; maps Cancelled to success.
Cargo.toml	Adds shared workspace dependencies for picker support.
Cargo.lock	Locks new transitive dependencies pulled in by dialoguer/ctrlc/console.

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[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-07-03 09:01 UTC · Rule: default · triggered by merge protections
• ✅ Checks passed · on draft merge queue: checking main (4efb5cb) and #1704 together #1706
• ✅ Merged — 2026-07-03 09:09 UTC · at 05cdf8eff07cb3258493f10b00a3b6eb3806189c · squash

This pull request spent 8 minutes 5 seconds in the queue, including 7 minutes 46 seconds running CI.

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