Function calculateCommitAttribution

src/utils/commitAttribution.ts:549–744

(
  states: AttributionState[],
  stagedFiles: string[],
)

 * Compares session baseline to committed state.
 */
export async function calculateCommitAttribution(
  states: AttributionState[],
  stagedFiles: string[],
): Promise<AttributionData> {
  const cwd = getAttributionRepoRoot()
  const sessionId = getSessionId()

  const files: Record<string, FileAttribution> = {}
  const excludedGenerated: string[] = []
  const surfaces = new Set<string>()
  const surfaceCounts: Record<string, number> = {}

  let totalClaudeChars = 0
  let totalHumanChars = 0

  // Merge file states from all sessions
  const mergedFileStates = new Map<string, FileAttributionState>()
  const mergedBaselines = new Map<
    string,
    { contentHash: string; mtime: number }
  >()

  for (const state of states) {
    surfaces.add(state.surface)

    // Merge baselines (earliest baseline wins)
    // Handle both Map and plain object (in case of serialization)
    const baselines =
      state.sessionBaselines instanceof Map
        ? state.sessionBaselines
        : new Map(
            Object.entries(
              (state.sessionBaselines ?? {}) as Record<
                string,
                { contentHash: string; mtime: number }
              >,
            ),
          )
    for (const [path, baseline] of baselines) {
      if (!mergedBaselines.has(path)) {
        mergedBaselines.set(path, baseline)
      }
    }

    // Merge file states (accumulate contributions)
    // Handle both Map and plain object (in case of serialization)
    const fileStates =
      state.fileStates instanceof Map
        ? state.fileStates
        : new Map(
            Object.entries(
              (state.fileStates ?? {}) as Record<string, FileAttributionState>,
            ),
          )
    for (const [path, fileState] of fileStates) {
      const existing = mergedFileStates.get(path)
      if (existing) {
        mergedFileStates.set(path, {