docs(agent): stack checkout no longer takes --author or --branch-prefix

[mergify-ci-bot]

mergify stack checkout was reworked in the 2026.8.28 CLI: --author and
--branch-prefix are gone, the positional argument now takes either a stack's
remote branch name or the URL of any pull request in the stack, and --branch
derives its default from the stack branch rather than from the stack name. The
Team Adoption page still told a teammate to run
mergify stack checkout feat/their-feature --author their-login, which the CLI
now rejects, and two pages listed checkout among the commands that accept
--branch-prefix. It is the one stack command that no longer does.

Separately, both the Concepts page and the merge queue's Stacked Pull Requests
page presented the Depends-On: marker as something every pushed stack
carries, and as what makes the queue treat the chain as a unit. A stack pushed
with --github-native carries no such marker, because GitHub's stacking API
holds the ordering instead, and the queue then handles it as a GitHub-native
stack: queued per member, landing bottom up. Both pages now say so and point at
the section that already documents that path.

Evidence: public/cli-schema.json for the flag and argument changes, and its
own --github-native help text for the missing header.

Open question: whether the branch-name form of the target deserves an example.
The schema says checkout accepts "its remote branch name", but a stack has one
remote branch per commit under a {prefix}/{name}/ path, so which string that
means is not obvious. I documented the pull request URL form, which the schema
states unambiguously, and mentioned the branch form without an example rather
than guess at one.

[mergify]

Merge Protections

🟢 All 6 merge protections satisfied — ready to merge.

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🟢 🤖 Continuous Integration

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🟢 Enforce conventional commit

Make sure that we follow https://www.conventionalcommits.org/en/v1.0.0/

• title ~= ^(fix|feat|internal|docs|style|refactor|perf|test|build|ci|chore|revert|ui)(?:\(.+\))?!?:

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🟢 📕 PR description

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🟢 🚦 Auto-queue

When all merge protections are satisfied, this pull request will be queued automatically.

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-09-01 07:53 UTC · Rule: default · triggered by merge protections
• ✅ Checks passed · on draft merge queue: checking #12633 on main (6b00195) #12635
• ✅ Merged — 2026-09-01 07:59 UTC · at 5ec50ee06e02796b094184b05e7f782789052356 · squash

This pull request spent 5 minutes 58 seconds in the queue, including 4 minutes 47 seconds running CI.

Required conditions to merge

• github-review-approved [🛡 GitHub repository ruleset rule Require pull request for default branch]
  • docs(agent): stack checkout no longer takes --author or --branch-prefix #12633
• schedule=Mon-Fri 09:00-17:30[Europe/Paris]
• all of [🛡 Merge Protections rule Enforce conventional commit]:
  • title ~= ^(fix|feat|internal|docs|style|refactor|perf|test|build|ci|chore|revert|ui)(?:\(.+\))?!?:
    • docs(agent): stack checkout no longer takes --author or --branch-prefix #12633
• all of [🛡 Merge Protections rule 👀 Review Requirements]:
  • any of:
    • #approved-reviews-by >= 2
      • docs(agent): stack checkout no longer takes --author or --branch-prefix #12633
    • author = dependabot[bot]
      • docs(agent): stack checkout no longer takes --author or --branch-prefix #12633
    • author = renovate[bot]
      • docs(agent): stack checkout no longer takes --author or --branch-prefix #12633
    • all of:
      • -head ~= ^docs-agent/
        • docs(agent): stack checkout no longer takes --author or --branch-prefix #12633
      • author = mergify-ci-bot
        • docs(agent): stack checkout no longer takes --author or --branch-prefix #12633
• all of [🛡 Merge Protections rule 📕 PR description]:
  • body ~= (?ms:.{48,})
    • docs(agent): stack checkout no longer takes --author or --branch-prefix #12633
• all of [🛡 Merge Protections rule 🔎 Reviews]:
  • #changes-requested-reviews-by = 0
    • docs(agent): stack checkout no longer takes --author or --branch-prefix #12633
  • #review-requested = 0
    • docs(agent): stack checkout no longer takes --author or --branch-prefix #12633
  • #review-threads-unresolved = 0
    • docs(agent): stack checkout no longer takes --author or --branch-prefix #12633
• all of [🛡 Merge Protections rule 🤖 Continuous Integration]:
  • all of:
    • check-success = build
    • check-success = lint
    • check-success = test
    • any of:
      • check-success = test-broken-links
      • label = ignore-broken-links
        • docs(agent): stack checkout no longer takes --author or --branch-prefix #12633
    • any of:
      • -head-repo-full-name~=^Mergifyio/
        • docs(agent): stack checkout no longer takes --author or --branch-prefix #12633
      • check-success=Cloudflare Pages