Alright here's how this works.



PR adds conflict resolution detection, helpers, and ui to file rendering.


## Highlevel API





You render a file with standard git conflict markers (<<<<<<, =======, etc.)





You get these options on file api:





mergeConflictActions:  ‘default’ | ‘none’ | (conflict, instance) => HTMLElement



 - by default we render a vscode-like api (Accept current change │ Accept incoming change │ Accept both)



 - you can also opt out of action bar w/ ‘none’


 
- you can also pass a custom thing and render your own ui





onMergeConflictAction => undefined: 
  - event delegation handler for click any of the actions rendered in the action bar.
  - This is optional, if you don’t supply we just resolve the file for you. If you do supply, then you need to manage. updating the contents yourself
  - note: this is only ever called if you do the default render path above (not custom).

## Conflict Detection

happens in getMergeConflictLineTypes.ts.

  1. It scans file lines once, top-to-bottom.
  2. It uses marker regexes:

  - <<<<<<< start
  - ||||||| base (optional, 3-way conflicts)
  - ======= separator
  - >>>>>>> end

  3. It keeps a stack of active conflicts (MergeConflictFrame) so nested conflicts work.

  - On start marker: push frame, stage=current
  - On base marker: stage=base
  - On separator: stage=incoming
  - On end marker: pop frame and finalize one MergeConflictRegion

  4. While inside a frame, non-marker lines are tagged by current stage:

  - current, base, or incoming
  - Marker lines are tagged as marker-start/base/separator/end
  - Lines outside conflicts are none

  5. When finalizing a region, it stores:

  - conflictIndex (0-based, parse order)
  - startLineIndex, separatorLineIndex, endLineIndex
  - optional baseMarkerLineIndex
  - line-number versions (+1) too

  6. Action row placement uses:

  - getMergeConflictActionLineNumber(conflict) = max(1, startLineNumber - 1)
    in the same file.

  If markers are malformed (for example missing separator/end), it won’t finalize a region for that frame.
  
## Interaction wiring (File component)

  - Default buttons use data-merge-conflict-action + data-merge-conflict-index.
  - File listens for clicks, validates resolution, resolves the region by conflictIndex, then
    emits payload.
    
## State ownership (controlled vs uncontrolled)

  - Controlled: if onMergeConflictAction exists, File calls it and does not mutate content
    internally.
  - Uncontrolled: File applies resolveMergeConflict(...) itself, then keeps an internal override
    (getEffectiveFile) until caller adopts/changes external content.
    

 Custom action UIs are slot-based (mergeConflictActions function + slot names) and managed via a
  small cache keyed by conflict slot name/region equality.



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