feat(rust): add mergify-core foundation types (Phase 1.2a)

[jd]

Populates mergify-core with the three type-system pieces every
ported command will depend on:

• exit_code::ExitCode — typed mirror of Python's ExitCode
  enum with the locked numeric values from docs/exit-codes.md. Code
  2 is reserved for clap argument errors, matching Python's Click
  reservation.
• error::CliError — top-level error enum with deterministic
  exit_code() mapping. Today it covers Configuration,
  InvalidState, StackNotFound, Conflict, Generic, and Io variants;
  HTTP and Git variants land alongside their implementations in
  1.2b / 1.2d.
• output::Output trait + StdioOutput impl — commands emit
  through a trait object so the --json vs human rendering
  decision is a single place (stdout purity invariant from Phase
  0.3 enforced by construction). Tests capture output via
  Arc<Mutex<Vec<u8>>> sinks.

Deferred to separate PRs so each is reviewable in isolation:

• 1.2b mergify-core::http — reqwest wrapper, retry, typed errors
• 1.2c colored/spinner affordances on top of StdioOutput
• 1.2d GitOps trait (only needed for stack commands)
• Config loading, interactive prompts — added as ported commands
  demand them

7 unit tests cover the locked exit-code values, the CliError -> ExitCode mapping, and the JSON/human split.

Co-Authored-By: Claude Opus 4.7 (1M context) noreply@anthropic.com

[jd]

This pull request is part of a Mergify stack:

#	Pull Request	Link
1	feat(rust): add mergify-core foundation types (Phase 1.2a)	#1280	👈
2	feat(rust): add mergify-core::http with retry + typed errors (Phase 1.2b)	#1281
3	feat(rust): port config validate to native Rust (Phase 1.3)	#1282
4	test: add port-inventory guard to catch un-ported Python commands	#1296
5	ci: add Rust release workflow targeting GitHub Release assets	#1297
6	feat(rust): port config simulate to native Rust (Phase 1.3b)	#1298
7	feat(rust): port ci scopes-send to native Rust (Phase 1.4)	#1300
8	feat(rust): port queue pause and unpause to native Rust (Phase 1.5)	#1301
9	feat(rust): port ci git-refs and ci queue-info to native Rust (Phase 1.6)	#1302

[mergify]

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[jd]

Revision history

#	Type	Changes	Date
1	initial	8f2f3d5	2026-04-21 13:13 UTC
2	rebase	8f2f3d5 → f1c0421	2026-04-21 13:13 UTC
3	content	f1c0421 → 56ba494
4	rebase	56ba494 → 1b5b259
5	content	1b5b259 → ddfcde3
6	rebase	ddfcde3 → 56033c1
7	rebase	56033c1 → 9d30ade	2026-04-23 19:02 UTC
8	rebase	9d30ade → 6eae5c0	2026-04-24 13:41 UTC

[Copilot]

Pull request overview

Adds the initial “foundation types” to mergify-core needed by ported Rust commands, covering structured exit codes, a top-level CLI error type, and a JSON/human output abstraction.

Changes:

• Introduce exit_code::ExitCode with fixed numeric values matching the documented contract (with code 2 reserved for clap usage errors).
• Add error::CliError with a deterministic CliError -> ExitCode mapping.
• Add output::Output trait and StdioOutput implementation (plus unit tests) to centralize JSON vs human rendering and stdout/stderr discipline.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
crates/mergify-core/src/output.rs	Introduces output abstraction + stdio implementation + tests for JSON/human behavior
crates/mergify-core/src/lib.rs	Exposes the new core modules and re-exports key types
crates/mergify-core/src/exit_code.rs	Defines structured exit codes and tests for locked numeric values
crates/mergify-core/src/error.rs	Defines CliError and its stable mapping to ExitCode with tests
crates/mergify-core/Cargo.toml	Adds serde/serde_json/thiserror dependencies for the new modules
Cargo.lock	Records the new Rust dependencies in the lockfile

---

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[mergify]

@jd this pull request is now in conflict 😩

Pull request has been modified.

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-04-27 05:23 UTC · Rule: default
• ✅ Checks passed · on draft merge queue: embarking main (a91b74d) and #1280 together #1306
• ✅ Merged — 2026-04-27 05:30 UTC · at 6eae5c07dd83d5f92c5f33003d84c58c8b120032 · squash

This pull request spent 7 minutes 23 seconds in the queue, including 7 minutes 5 seconds running CI.

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