squash-merge-content-preservation-vs-ancestor-check SKILL.md skillA
squash-merge-content-preservation-vs-ancestor-check from wan-huiyan/agent-traffic-control is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add wan-huiyan/agent-traffic-control/squash-merge-content-preservation-vs-ancestor-check@v1.0.0Pins v1.0.0 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- wan-huiyan/agent-traffic-control
- Path
plugins/agent-traffic-control/skills/squash-merge-content-preservation-vs-ancestor-check/SKILL.md- Versions recorded
- 2
- Latest version
- v1.0.0, committed Jul 8, 2026
- First version recorded
- May 29, 2026
- Size
- 8,655 bytes
- Repository stars
- 3
- License
- MIT
Use when verifying that an upstream commit (e.g., a colleague's work, a feature-branch commit) is preserved in a target branch after a propagation PR has merged — and the verification script uses `git merge-base --is-ancestor <upstream-sha> <target-branch>`. If the merge mode was **squash**, that ancestor check ALWAYS returns non-zero even when content is preserved verbatim, because squash collapses every commit into a single new SHA on the target. Apply this skill when: (1) preservation…
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Squash Merge Content Preservation vs Ancestor Check ## Problem Your verification script says: ```bash git merge-base --is-ancestor 0b6303e76 origin/main && echo "OK" || echo "MISSING" # Prints: MISSING ``` … but `wc -l <signature-file>` returns the expected line counts and `grep -c <signature-string>` returns ≥ the expected ref count. The exit code from `is-ancestor` is non-zero **even though every byte of the upstream work is preserved on the target branch**. The "MISSING" verdict is wrong. Root cause: a squash merge collapses every commit on the source branch into a **single new commit** on the target. The original SHAs (including the upstream commit you're checking) never appear in the target's history. `is-ancestor` returns "false" because the SHA truly isn't an ancestor of the merge commit — but the SHA's *content* is preserved verbatim inside the squash commit. This trap fires whenever: - A handoff prompt or skill mixes ancestor-based checks with content-based checks for the same preservation claim - The handoff was written before the merge mode was decided - The verification template assumed fast-forward / no-ff (which preserves …
Read the whole file at its exact version.
How to install
mdr add wan-huiyan/agent-traffic-control/squash-merge-content-preservation-vs-ancestor-check@sha256:2f1e5e26f21e23d2The line at the top of this page pins the label v1.0.0, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_gezvt5imsrsuyrzq)
3 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 2 versions of this file, between May 29, 2026 and Jul 8, 2026, about one every 40 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| v1.0.0 latest | 2026-07-08 | f1254dd | 8,655 B | A | view · diff |
| v1.0.0 | 2026-05-29 | 059688a | 8,624 B | A | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (8655 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
wan-huiyan/agent-traffic-control · 3 stars · license MIT · pushed 2026-09-22 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_gezvt5imsrsuyrzq GET https://markdownregistry.com/api/v1/resolve?ref=wan-huiyan/agent-traffic-control/squash-merge-content-preservation-vs-ancestor-check GET https://markdownregistry.com/api/v1/blob/2f1e5e26f21e23d2587d460d8f5b74baec608ba77d8d50b664c7c0e534700855
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.