feat: install shell completions for mergify-cli

[kozlek]

What

Wire mergify-cli's new mergify completions <shell> command into the formula so brew install ships first-class shell completions (bash/zsh/fish) automatically — no more asking users to generate and source them by hand.

def install
  bin.install "mergify"
  generate_completions_from_executable(bin/"mergify", "completions")
end

Why now

mergify-cli 2026.6.25.1 (just bumped in #24) added a completions subcommand backed by clap_complete:

$ mergify completions --help
Usage: mergify completions [OPTIONS] <SHELL>
  <SHELL>  ... [possible values: bash, elvish, fish, powershell, zsh]

It's pure clap introspection — it prints the script to stdout with no network or async runtime — so it's safe to invoke at install time. generate_completions_from_executable(bin/"mergify", "completions") matches that CLI shape exactly (it runs mergify completions {bash,zsh,fish}).

This had to land after #24: the previous pinned release (2026.6.18.1) had no completions command, so the install-time call would have failed.

Test

Added a test do assertion:

assert_match "#compdef mergify", shell_output("#{bin}/mergify completions zsh")

Verified locally against the real 2026.6.25.1 aarch64-apple-darwin binary (checksum matches SHA256SUMS); brew style passes clean.

🤖 Generated with Claude Code

[mergify]

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[Copilot]

Pull request overview

This PR updates the mergify-cli Homebrew formula to automatically generate and install shell completions during brew install, leveraging the CLI’s new mergify completions <shell> subcommand.

Changes:

• Generate bash/zsh/fish completions at install time via generate_completions_from_executable.
• Add a formula test asserting the zsh completion output contains the expected #compdef header.

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[mergify]

Queued — the merge queue status continues in this comment ↓.

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-06-25 11:47 UTC · Rule: default · triggered by merge protections
• ✅ Checks skipped · PR is already up-to-date
• ✅ Merged — 2026-06-25 11:47 UTC · at 642fd9a883b2273ca46ce309e8b17fec1954c3bf · squash

This pull request spent 9 seconds in the queue, including 2 seconds running CI.

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• all of [🛡 Merge Protections rule Enforce conventional commit]:
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    • feat: install shell completions for mergify-cli #25
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    • feat: install shell completions for mergify-cli #25
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    • feat: install shell completions for mergify-cli #25
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    • feat: install shell completions for mergify-cli #25
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    • feat: install shell completions for mergify-cli #25
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    • feat: install shell completions for mergify-cli #25
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