feat(stack): add mergify stack squash command

[jd]

Add "mergify stack squash SRC... into TARGET [-m MESSAGE]" which reorders
SRC commits adjacent to TARGET and folds them in without opening an
editor. Without -m, TARGET's message is kept (via the fixup rebase
action). With -m, the rebase inserts an exec git commit --amend -m ...
line right after the last fixup source, which runs while HEAD still
points at the combined target — so prepare-commit-msg re-attaches the
Change-Id normally.

Errors when SRC == TARGET, when a SRC is duplicated, or when a SRC or
TARGET prefix is unknown. Supports --dry-run.

Click does not allow two positionals when one is variadic, so the CLI
takes a single tokens tuple and parses "SRC... into TARGET" manually
(_parse_squash_tokens); parser edge cases are covered by unit tests.

Also documents the squash command in skills/mergify-stack/SKILL.md.

[jd]

This pull request is part of a Mergify stack:

#	Pull Request	Link
1	feat(stack): add mergify stack squash command	#1266	👈

[mergify]

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[jd]

Revision history

#	Type	Changes	Date
1	initial	6e5abfd	2026-04-20 14:08 UTC
2	content	6e5abfd → 96320ff	2026-04-20 14:08 UTC
3	rebase	96320ff → 24e8198	2026-04-21 08:01 UTC
4	content	24e8198 → dd97d10	2026-04-21 08:53 UTC

[mergify]

@jd this pull request is now in conflict 😩

[Copilot]

Pull request overview

Adds a new non-interactive mergify stack squash command to combine one or more “SRC” commits into a “TARGET” commit (optionally amending the final message), intended to avoid interactive rebases/editors while working with stacked PRs.

Changes:

• Implement stack_squash() to reorder SRC commits next to TARGET and fold them via a scripted interactive rebase (with optional amend exec for -m).
• Add the mergify stack squash SRC... into TARGET [-m ...] CLI command plus a small token parser to work around Click positional limitations.
• Add unit tests for both the token parser and squash behavior; document the new command in the skill doc.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

File	Description
skills/mergify-stack/SKILL.md	Documents the new stack squash workflow and adds examples.
mergify_cli/tests/stack/test_squash_cli.py	Adds unit tests for parsing SRC... into TARGET tokens.
mergify_cli/tests/stack/test_squash.py	Adds integration-style tests validating reorder/fold behavior, errors, and dry-run for squash.
mergify_cli/stack/squash.py	Replaces the previous placeholder with the actual stack_squash implementation (incl. optional amend exec).

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[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-04-21 13:13 UTC · Rule: default
• ✅ Checks passed · on draft merge queue: embarking main (b314393) and #1266 together #1283
• ✅ Merged — 2026-04-21 13:21 UTC · at dd97d1084ea078e0df7d41a1038c8d933505aad5 · squash

This pull request spent 7 minutes 45 seconds in the queue, including 7 minutes 18 seconds running CI.

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      • feat(stack): add mergify stack squash command #1266
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      • feat(stack): add mergify stack squash command #1266
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    • feat(stack): add mergify stack squash command #1266
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    • feat(stack): add mergify stack squash command #1266
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