#3797 feat(desktop): expand a whole file from its header, and show a file that only moved as its lines

Summary

Part of the stage-cli features the developer chose: expand or collapse a whole file, as stage-cli's file header does (file-diff-list.tsx:522, lib/file-expansion-context.tsx, lib/full-file-preview.ts). Built on #3762's readTexts and stacked on the header actions PR.

• Expand full file / Collapse to changes.
  • A compact header button (UnfoldVertical/FoldVertical, with a pressed state and a tooltip) draws the whole file, every unchanged line among its changes, until it's pressed again.
  • It's offered only on files #3762 lets expand: changed in place or moved with changes, a patch drawn, not a secret path.
  • It's also offered on files that only moved. It's never offered on images drawn as pictures.
• How the file gets drawn. Pierre 1.5.2's CodeView only has a list-wide expandUnchanged. So instead of driving expandHunk across a file's hunks, the item's fileDiff is replaced with parseDiffFromFile(before, after, { context: MAX }): one hunk holding every line.
  • It's cached per texts object, so redrawing a file for its notes keeps the same diff.
  • Collapse re-parses the patch fresh, which returns the file to its changes, gaps closed.
  • It survives virtualization by construction: the item's diff is the whole file, so scrolling away and back draws it the same. I checked this in the harness: lines 1… are still drawn after scrolling 30,000 px away and back.
• Reading the file. It goes through the same door as the gaps (FileTexts.read): one TASKS_FILE read at headSha, blobSha-checked, kept for the answer's life.
  • Nothing is read until the button is pressed, and a file whose gaps were already opened isn't read again.
  • A refused read leaves the file as it is and shows the refusal line, as a gap's refusal does.
• A pure rename (no hunks) still says "renamed without changes" at first. Once expanded, it shows its whole text as unchanged lines (textsOf treats the text before as the text after).
  • stage-cli shows these up front, because its CLI sends both sides of every file.
  • Here that would be one GitHub read per renamed file on every open, so it's behind the same button.
  • The note itself offers it too: "File renamed without changes to its contents. · Show file", a link-toned TextButton that runs the same toggle.
• Threads stay anchored, since annotations are keyed by side and line. Commenting stays limited to lines GitHub accepts (commentLines is unchanged).

Screenshots

PR #2908's build.mjs in the harness (Chromium).

	light	dark
the button's hint
expanded, lines from 1
a pure rename's Show file (PR #2855)

Evidence

• tsc --noEmit for panel and desktop: clean.
• ./scripts/oxlint.sh: 0 errors.
• pnpm knip: clean.
• ./scripts/repository-checks.sh: passed.
• vitest run --project panel --project desktop: 231 files, 2366 tests passed, run with this change in the tree.
• New test in agent-changes-tab.test.ts:
  • An added file is offered nothing; a file that only moved starts as its notice.
  • Expanding hands the bundle whole texts. For the moved file, pressed through its note's Show file, before equals after and it's no longer a lead.
  • Collapse to changes drops whole.
  • Re-expanding reads nothing new: two files, two reads.

Invariants

• Checks green locally, as listed above.
• JSON Schema goldens unchanged.
• Behaviour tested.
• No new as.
• No raw async primitives.
• Test count +1.
• Deps unchanged.

Made with Luke

Review fixes (Devin)

• A pure rename shown whole drew nothing: two identical texts diff to no hunk. diff-view/whole-diff.ts now lays such a file out as one context hunk. A file with no lines keeps its notice.
• Threads on a file drawn whole are placed against every line of its texts, not just the patch's rows. This covers a pure rename and threads outside the hunks of an expanded file.
• A stale whole read (from before a refresh) is dropped instead of overwriting files expanded since.