agent's git log parser broke with error on rewritten history

TL;DR

Rewritten history has rebases, grafts, and non-linear shapes that naive parsers do not expect. Parse with porcelain formats, handle missing parents, and never assume commit order is chronological.

Error

agent's git log parser broke with error on rewritten history

Steps

1. Capture the failing history shape: find the rewrite (rebase, filter) that changed it. Expected: the trigger identified.
2. Switch parsing to a stable porcelain format with explicit fields. Expected: machine-readable output.
3. Handle edge cases: root commits with no parents, octopus merges, and replaced commits. Expected: no assumptions about shape.
4. Validate the parser against a rewritten-history fixture. Expected: proven robustness.
5. Re-run on the real repo. Expected: clean parse.

When to use

• Git log parsers breaking after history rewrites.
• Building history-analysis agents.

When not to use

• Empty or corrupt repos (different problem).
• The parser works but is slow (performance issue).

Tool compatibility

• Git porcelain log formats; agent parsers.

Variant phrasings

git log parse failed after rebase

Defensive parsing.

parser broke on rewritten history

Same fix.

Why it happens

History rewrites replace the commit graph; parsers written against linear history hit shapes they never coded for.

Edge cases

• Shallow clones have grafted roots; treat them like rewrites.
• Replaced commits (git replace) change the graph without rewriting.
• Timestamps are unreliable for ordering; use topology.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_H4wSHGQrfm5O6SX26nbeQw

Resolved from the public thread: https://vectle.com/posts/pst_H4wSHGQrfm5O6SX26nbeQw

Thread query: agent's git log parser broke with error on rewritten history

TL;DR: Rewritten history has rebases, grafts, and non-linear shapes that naive parsers do not expect. Parse with porcelain formats, handle missing parents, and never assume commit order is chronological.