feat(FN-5154): complete Step 0 — add done-range attribution helper

Fusion-Task-Id: FN-5154
Fusion-Task-Lineage: 1ca8d162-343b-4d55-bcba-c34efa331ac4

packages/dashboard/src/routes/attribute-done-range-files.ts

@@ -0,0 +1,108 @@
+type AttributionSource = "trailer" | "subject-prefix" | "bracketed-prefix" | "none";
+
+export interface DoneRangeAttributionOptions {
+  worktreePath: string;
+  baseRef: string;
+  taskId: string;
+  runGit: (args: string[]) => Promise<string>;
+}
+
+export interface DoneRangeAttributionResult {
+  files: string[];
+  ownCommitShas: string[];
+  foreignCommitCount: number;
+}
+
+function extractAttributedTaskId(body: string): string | null {
+  const trailerPattern = /(?:^|\n)(?:Fusion-Task-Id|Task-Id):\s*(\S+)\s*(?:\n|$)/gim;
+  let match: RegExpExecArray | null = null;
+  let last: RegExpExecArray | null = null;
+  while (true) {
+    match = trailerPattern.exec(body);
+    if (!match) break;
+    last = match;
+  }
+  return last?.[1] ?? null;
+}
+
+function extractTaskIdFromSubject(subject: string): {
+  attributedTaskId: string | null;
+  source: Extract<AttributionSource, "subject-prefix" | "bracketed-prefix" | "none">;
+} {
+  if (!subject) {
+    return { attributedTaskId: null, source: "none" };
+  }
+
+  const conventional =
+    /^(?:feat|fix|test|chore|docs|refactor|perf|build|ci|style|revert)\s*\(([A-Z]+-\d+)\)!?:/i.exec(subject);
+  if (conventional?.[1]) {
+    return { attributedTaskId: conventional[1].toUpperCase(), source: "subject-prefix" };
+  }
+
+  const bracketed = /^\s*\[([A-Z]+-\d+)\]/i.exec(subject);
+  if (bracketed?.[1]) {
+    return { attributedTaskId: bracketed[1].toUpperCase(), source: "bracketed-prefix" };
+  }
+
+  const colon = /^\s*([A-Z]+-\d+):/i.exec(subject);
+  if (colon?.[1]) {
+    return { attributedTaskId: colon[1].toUpperCase(), source: "subject-prefix" };
+  }
+
+  return { attributedTaskId: null, source: "none" };
+}
+
+function taskIdsMatch(a: string | null, b: string): boolean {
+  return Boolean(a) && a.toUpperCase() === b.toUpperCase();
+}
+
+export async function filterFilesToOwnTaskCommits(opts: DoneRangeAttributionOptions): Promise<DoneRangeAttributionResult> {
+  const logOutput = await opts.runGit(["log", "--format=%H%x00%s%x00%B%x1e", `${opts.baseRef}..HEAD`]);
+
+  if (!logOutput.trim()) {
+    return { files: [], ownCommitShas: [], foreignCommitCount: 0 };
+  }
+
+  const fileSet = new Set<string>();
+  const ownCommitShas: string[] = [];
+  let foreignCommitCount = 0;
+
+  const records = logOutput
+    .split("\x1e")
+    .map((record) => record.trim())
+    .filter(Boolean);
+
+  for (const record of records) {
+    const [sha = "", subject = "", ...bodyParts] = record.split("\x00");
+    if (!sha) continue;
+    const body = bodyParts.join("\x00");
+
+    const trailerAttributedTaskId = extractAttributedTaskId(body);
+    const subjectAttribution = trailerAttributedTaskId
+      ? { attributedTaskId: null, source: "none" as const }
+      : extractTaskIdFromSubject(subject);
+    const attributedTaskId = trailerAttributedTaskId ?? subjectAttribution.attributedTaskId;
+
+    if (taskIdsMatch(attributedTaskId, opts.taskId)) {
+      ownCommitShas.push(sha);
+    } else {
+      foreignCommitCount += 1;
+    }
+  }
+
+  for (const sha of ownCommitShas) {
+    const diffTreeOutput = await opts.runGit(["diff-tree", "--no-commit-id", "--name-only", "-r", sha]);
+    for (const file of diffTreeOutput
+      .split("\n")
+      .map((line) => line.trim())
+      .filter(Boolean)) {
+      fileSet.add(file);
+    }
+  }
+
+  return {
+    files: [...fileSet].sort((a, b) => a.localeCompare(b)),
+    ownCommitShas,
+    foreignCommitCount,
+  };
+}