agent's diff parser failed on binary file renames in docs sync

TL;DR

Parse renames from git diff --name-status instead of the patch text: binary renames appear as an R line with old and new paths, while the patch body is just a "Binary files ... differ" stub with no headers to parse. Parsers that only understand text hunks drop these silently. Read the name-status lines and you get every rename for free.

agent's diff parser failed on binary file renames in docs sync

Steps

1. Reproduce with the right plumbing: run git diff --name-status HEAD~1 HEAD on a commit that renames a binary. Expected: a line like R100 old/path/image.png new/path/image.png. The patch text for the same commit shows only Binary files ... differ with no file headers, which is what breaks naive parsers.
2. Change the parser to consume name-status lines: for every line starting with R, strip the similarity score and record the old-to-new path pair. Handle A, D, and M lines the same way for adds, deletes, and modifies.
3. Treat the binary stub as opaque: when the patch body says the files differ and are binary, skip hunk parsing for that file and use the path pair from step 2. Expected: no more parse exceptions on binary commits.
4. Update the sync mapping: renamed binaries keep their docs references working by rewriting links from the old path to the new path. Expected: the built docs have no broken image or asset links after the rename.
5. Test on a fixture commit containing a renamed image and a renamed PDF: the sync should complete and report both renames. Expected: exit 0 and both new paths in the sync log.

Use this when

• docs sync breaks on commits that rename images, PDFs, or other binaries
• renamed assets vanish from generated docs
• your diff parser assumes every file has text hunks

Not for this skill when

• renames of text files fail too (general rename handling bug, not binary-specific)
• the sync fails on all binary files, renamed or not (binary handling bug)
• git itself reports the rename wrong (check rename detection config first)

Variant phrasings

• diff parser choked on renamed png in docs sync
• binary file rename broke docs sync
• agent dropped renamed images during sync

Why it happens

Text diffs carry file headers that parsers key on, but binary diffs carry only a one-line "differ" notice. A parser written against text hunks finds no headers, throws or skips the file, and the sync never learns the new path, so references to the renamed asset break.

Edge cases

• Similarity below the rename threshold shows as separate D plus A lines: the sync should handle that pair too, or lower the threshold.
• Executable-bit-only changes on binaries produce a mode-change line with no content diff: do not treat it as a rename.
• Very large binaries may be excluded from diffs entirely by config: fall back to comparing file listings.
• Case-only renames on case-insensitive filesystems can confuse path mapping: normalize case when matching.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_L4aLzBGIMsDXrrgBotVfQg