refactor: extract git worktree parser from atlas hook

src/shared/git-worktree/git-worktree.test.ts

@@ -0,0 +1,51 @@
+/// <reference types="bun-types" />
+
+import { describe, expect, test } from "bun:test"
+import { formatFileChanges, parseGitDiffNumstat, parseGitStatusPorcelain } from "./index"
+
+describe("git-worktree", () => {
+  test("#given status porcelain output #when parsing #then maps paths to statuses", () => {
+    const porcelain = [
+      " M src/a.ts",
+      "A  src/b.ts",
+      "?? src/c.ts",
+      "D  src/d.ts",
+    ].join("\n")
+
+    const map = parseGitStatusPorcelain(porcelain)
+    expect(map.get("src/a.ts")).toBe("modified")
+    expect(map.get("src/b.ts")).toBe("added")
+    expect(map.get("src/c.ts")).toBe("added")
+    expect(map.get("src/d.ts")).toBe("deleted")
+  })
+
+  test("#given diff numstat and status map #when parsing #then returns typed stats", () => {
+    const porcelain = [" M src/a.ts", "A  src/b.ts"].join("\n")
+    const statusMap = parseGitStatusPorcelain(porcelain)
+
+    const numstat = ["1\t2\tsrc/a.ts", "3\t0\tsrc/b.ts", "-\t-\tbin.dat"].join("\n")
+    const stats = parseGitDiffNumstat(numstat, statusMap)
+
+    expect(stats).toEqual([
+      { path: "src/a.ts", added: 1, removed: 2, status: "modified" },
+      { path: "src/b.ts", added: 3, removed: 0, status: "added" },
+      { path: "bin.dat", added: 0, removed: 0, status: "modified" },
+    ])
+  })
+
+  test("#given git file stats #when formatting #then produces grouped summary", () => {
+    const summary = formatFileChanges([
+      { path: "src/a.ts", added: 1, removed: 2, status: "modified" },
+      { path: "src/b.ts", added: 3, removed: 0, status: "added" },
+      { path: "src/c.ts", added: 0, removed: 4, status: "deleted" },
+    ])
+
+    expect(summary).toContain("[FILE CHANGES SUMMARY]")
+    expect(summary).toContain("Modified files:")
+    expect(summary).toContain("Created files:")
+    expect(summary).toContain("Deleted files:")
+    expect(summary).toContain("src/a.ts")
+    expect(summary).toContain("src/b.ts")
+    expect(summary).toContain("src/c.ts")
+  })
+})