Commit Composer (Preview) fails on commits containing binary files: "cannot apply binary patch without full index line"

[nshepperd]

Description

Recomposing any commit that contains a binary file (added or modified) fails when committing. This happens in every recompose entry point that uses the Commit Composer (Preview) webview: commit graph "Recompose Commits From Here (Preview)", interactive-rebase "Recompose" button and I assume also the compose commits button on the left gitlens extension panel. However the commit graph Recompose Branch option does work.

Steps to reproduce

# Create a repo with a single commit that adds a binary file:
mkdir gitlens-binary-recompose-bug && cd gitlens-binary-recompose-bug
git init -b main
git commit --allow-empty -m "root"

# any file git treats as binary works — an image, a zip, etc.
printf '\x89PNG\r\n\x1a\n\x00\x01\x02\x03 binary content here' > logo.png
git add logo.png
git commit -m "Add logo.png"

code .
# Open the Commit Graph (or the Commits view).
# Right-click the "Add logo.png" commit → "Recompose Commits From Here (Preview)".
# Recompose commits -> Create 1 Commit

The commit fails with this message:

Failed to commit changes: error: cannot apply binary patch to 'logo.png' without full index line error: logo.png: patch does not apply

GitLens Version

18.2.0

VS Code Version

Version: 1.123.0
Commit: 6a44c352bd24569c417e530095901b649960f9f8
Date: 2026-06-03T11:29:03+02:00
Electron: 42.2.0
ElectronBuildId: 14159160
Chromium: 148.0.7778.97
Node.js: 24.15.0
V8: 14.8.178.14-electron.0
OS: Linux x64 7.0.12-arch1-1

Git Version

git version 2.54.0

Logs, Screenshots, Screen Captures, etc

No response

[nshepperd]

I had Claude investigate it, and produce a fix. This is on my my branch https://github.com/nshepperd/vscode-gitlens/tree/bug/b5405. I confirmed by hand that recompose with binary files actually works with these fixes (both on the test case and my real repo that prompted this investigation).

This is what he says (you do not actually have to read this):

Commit Composer fails on commits containing binary files

Root cause: every Commit Composer (Preview) entry point uses a legacy path that collects a diff, parses it into hunks, reassembles a patch per commit, and replays it through git apply. That path was never binary-aware. (The graph's inline recomposer works because it uses @gitkraken/compose-tools, which handles binary correctly.)

It surfaced as five sequential failures — fixing each revealed the next:

#	Symptom	Cause	Fix
1	cannot apply binary patch … without full index line	getDiff ran git diff without --binary → binary files came through as the abbreviated Binary files … differ marker (no patch body, short index)	Added opt-in binary flag to getDiff; Composer diff collection (getComposerDiffs, calculateCombinedDiffBetweenCommits) passes it
2	corrupt binary patch … no-content-change	createCombinedDiffForCommit trimmed the binary patch (stripping the terminating blank line) and injected a synthesized hunk line + duplicated body	Emit binary file diffs verbatim (the parsed diffHeader is already the complete per-file diff)
3	Output diff does not match input	post-apply validateResultingDiff re-collected the result diff without --binary, so its hash couldn't match the now---binary input	Pass binary: true there too
4	Your request is too large	the base85 GIT binary patch body (a 54 MB apk → ~68 MB) was serialized into the AI requests (generateCommits hunks + generateCommitMessage patch)	New redactBinaryHunkContent replaces binary bodies with a Binary file placeholder before sending to the model
5	VS Code froze on the "Composition Summary" / "Files changed" panel	the webview received the full binary bodies and tried to render base85	Redact binary content at all webview hunk sends too

Key invariant: redaction (4 & 5) only affects what's sent to the model and webview. The real hunks (this._hunks) are kept intact and used for apply by index, so commits still contain the exact binary bytes.

Takeaway: these are one root cause in five places — the apply path needs full binary patches; the AI and UI paths must never see them. Net surface area: getDiff (+binary option) and the Composer's diff collection, reassembly, validation, and redaction. A longer-term fix is routing the Composer through @gitkraken/compose-tools (already used by the working graph recomposer), which handles all of this.