Preserve renames in committed file diffs (#6895)

* fix(git): preserve renames in committed file diffs Follow the requested destination through rename detection so the patch agrees with commit history instead of showing the whole file as newly added. * test(git): keep rename fixtures valid across platforms * fix(git): keep added copies out of committed rename diffs Detect rename sources across the first-parent commit before narrowing the patch. Follow mode also detected copies, causing added files to open as partial diffs against unchanged files. * perf(git): share committed rename discovery across file requests Opening a commit requests all of its file diffs concurrently. Share pending and completed rename scans for immutable commit IDs in a bounded cache, while symbolic refs always read fresh metadata. --------- Co-authored-by: paseo-bot[bot] <266920839+paseo-bot[bot]@users.noreply.github.com>
2026-10-28 20:22:45 +00:00 · 2026-10-15 07:05:42 +02:00
parent 9ab99a6e1e
commit 5c108f345c
3 changed files with 303 additions and 4 deletions
@@ -3,7 +3,8 @@ import { mkdirSync, mkdtempSync, realpathSync, rmSync, writeFileSync } from "fs"
 import { tmpdir } from "os";
 import { join } from "path";
 import { afterEach, describe, expect, it } from "vitest";
-import { getCommitFileDiff } from "./checkout-git.js";
+import { getCommitFileDiff, listCheckoutCommits } from "./checkout-git.js";
+import { startGitCommandMetrics, stopGitCommandMetrics } from "./run-git-command.js";

 const tempDirs: string[] = [];

@@ -44,6 +45,75 @@ function headSha(repoDir: string): string {
 }

 describe("getCommitFileDiff", () => {
+  it.each(["new.txt", "with spaces.txt"])("preserves a rename-only commit to %s", async (name) => {
+    const repoDir = initRepo();
+    commitFile(repoDir, "old.txt", "same\n", "initial");
+    git(["mv", "old.txt", name], repoDir);
+    git(["-c", "commit.gpgsign=false", "commit", "-m", "rename"], repoDir);
+    const sha = headSha(repoDir);
+
+    const history = await listCheckoutCommits({ cwd: repoDir });
+    expect(history.commits.find((commit) => commit.sha === sha)?.files).toEqual([
+      { path: name, status: "renamed", additions: 0, deletions: 0 },
+    ]);
+    expect(await getCommitFileDiff({ cwd: repoDir, sha, path: name })).toEqual({
+      path: name,
+      isNew: false,
+      isDeleted: false,
+      additions: 0,
+      deletions: 0,
+      hunks: [],
+    });
+  });
+
+  it.each(["new.txt", "目录.txt"])(
+    "preserves the edits in a committed rename to %s",
+    async (name) => {
+      const repoDir = initRepo();
+      commitFile(repoDir, "old.txt", "same\nkeep\nlast\n", "initial");
+      git(["mv", "old.txt", name], repoDir);
+      writeFileSync(join(repoDir, name), "same\nKEEP\nlast\n");
+      git(["add", "."], repoDir);
+      git(["-c", "commit.gpgsign=false", "commit", "-m", "rename and edit"], repoDir);
+      const sha = headSha(repoDir);
+
+      const history = await listCheckoutCommits({ cwd: repoDir });
+      expect(history.commits.find((commit) => commit.sha === sha)?.files).toEqual([
+        { path: name, status: "renamed", additions: 1, deletions: 1 },
+      ]);
+      const file = await getCommitFileDiff({ cwd: repoDir, sha, path: name });
+      expect(file).toMatchObject({
+        path: name,
+        isNew: false,
+        isDeleted: false,
+        additions: 1,
+        deletions: 1,
+      });
+      expect(file?.hunks.flatMap((hunk) => hunk.lines)).toEqual(
+        expect.arrayContaining([
+          expect.objectContaining({ type: "remove", content: "keep" }),
+          expect.objectContaining({ type: "add", content: "KEEP" }),
+        ]),
+      );
+    },
+  );
+
+  it.skipIf(process.platform === "win32")("preserves a rename to a quoted filename", async () => {
+    const repoDir = initRepo();
+    const name = 'new "draft".txt';
+    commitFile(repoDir, "old.txt", "same\n", "initial");
+    git(["mv", "old.txt", name], repoDir);
+    git(["-c", "commit.gpgsign=false", "commit", "-m", "rename"], repoDir);
+    expect(await getCommitFileDiff({ cwd: repoDir, sha: headSha(repoDir), path: name })).toEqual({
+      path: name,
+      isNew: false,
+      isDeleted: false,
+      additions: 0,
+      deletions: 0,
+      hunks: [],
+    });
+  });
+
  it("returns the parsed diff for a modified file in a commit", async () => {
    const repoDir = initRepo();
    commitFile(repoDir, "foo.txt", "a\nb\nc\n", "initial");
@@ -78,6 +148,78 @@ describe("getCommitFileDiff", () => {
    expect(file?.deletions).toBe(0);
  });

+  it.each([
+    ["exact", "line1\nline2\nline3\nline4\nline5\nline6\n"],
+    ["edited", "line1\nline2\nline3\nline4\nline5\nCHANGED\n"],
+  ])("shows an added %s copy as a new file", async (_kind, addedContent) => {
+    const repoDir = initRepo();
+    commitFile(repoDir, "source.txt", "line1\nline2\nline3\nline4\nline5\nline6\n", "initial");
+    commitFile(repoDir, "added.txt", addedContent, "add similar file");
+    const sha = headSha(repoDir);
+
+    const history = await listCheckoutCommits({ cwd: repoDir });
+    expect(history.commits.find((commit) => commit.sha === sha)?.files).toEqual([
+      { path: "added.txt", status: "added", additions: 6, deletions: 0 },
+    ]);
+    const file = await getCommitFileDiff({ cwd: repoDir, sha, path: "added.txt" });
+    expect(file).toMatchObject({
+      path: "added.txt",
+      isNew: true,
+      isDeleted: false,
+      additions: 6,
+      deletions: 0,
+    });
+    expect(
+      file?.hunks
+        .flatMap((hunk) => hunk.lines)
+        .filter((line) => line.type !== "header")
+        .map(({ type, content }) => ({ type, content })),
+    ).toEqual(
+      addedContent
+        .trimEnd()
+        .split("\n")
+        .map((content) => ({ type: "add", content })),
+    );
+  });
+
+  it("shares commit rename discovery across concurrent and later file requests", async () => {
+    const repoDir = initRepo();
+    commitFile(repoDir, "old.txt", "same\n", "initial");
+    git(["mv", "old.txt", "new.txt"], repoDir);
+    commitFile(repoDir, "added.txt", "added\n", "rename and add");
+    const sha = headSha(repoDir);
+
+    startGitCommandMetrics();
+    try {
+      const [renamed, added] = await Promise.all([
+        getCommitFileDiff({ cwd: repoDir, sha, path: "new.txt" }),
+        getCommitFileDiff({ cwd: repoDir, sha, path: "added.txt" }),
+      ]);
+      expect(renamed).toMatchObject({ isNew: false, additions: 0, deletions: 0 });
+      expect(added).toMatchObject({ isNew: true, additions: 1, deletions: 0 });
+      expect(await getCommitFileDiff({ cwd: repoDir, sha, path: "new.txt" })).toEqual(renamed);
+    } finally {
+      const metrics = stopGitCommandMetrics();
+      expect(metrics.commands.filter(({ args }) => args.includes("--name-status"))).toHaveLength(1);
+    }
+  });
+
+  it("rediscovers renames when a symbolic commit ref moves", async () => {
+    const repoDir = initRepo();
+    commitFile(repoDir, "old.txt", "same\n", "initial");
+    expect(await getCommitFileDiff({ cwd: repoDir, sha: "HEAD", path: "old.txt" })).toMatchObject({
+      isNew: true,
+      additions: 1,
+    });
+    git(["mv", "old.txt", "new.txt"], repoDir);
+    git(["-c", "commit.gpgsign=false", "commit", "-m", "rename"], repoDir);
+    expect(await getCommitFileDiff({ cwd: repoDir, sha: "HEAD", path: "new.txt" })).toMatchObject({
+      isNew: false,
+      additions: 0,
+      deletions: 0,
+    });
+  });
+
  it("returns null for a path not changed in the commit", async () => {
    const repoDir = initRepo();
    commitFile(repoDir, "foo.txt", "a\n", "initial");
@@ -89,6 +231,59 @@ describe("getCommitFileDiff", () => {
    expect(file).toBeNull();
  });

+  it("does not follow an unchanged file back to an earlier commit", async () => {
+    const repoDir = initRepo();
+    commitFile(repoDir, "foo.txt", "same\n", "initial");
+    commitFile(repoDir, "other.txt", "other\n", "unrelated change");
+    expect(
+      await getCommitFileDiff({ cwd: repoDir, sha: headSha(repoDir), path: "foo.txt" }),
+    ).toBeNull();
+  });
+
+  it("returns the added file in a root commit and the deleted file in its deletion commit", async () => {
+    const repoDir = initRepo();
+    commitFile(repoDir, "foo.txt", "same\n", "initial");
+    expect(
+      await getCommitFileDiff({ cwd: repoDir, sha: headSha(repoDir), path: "foo.txt" }),
+    ).toMatchObject({
+      isNew: true,
+      isDeleted: false,
+      additions: 1,
+      deletions: 0,
+    });
+    git(["rm", "foo.txt"], repoDir);
+    git(["-c", "commit.gpgsign=false", "commit", "-m", "delete"], repoDir);
+    expect(
+      await getCommitFileDiff({ cwd: repoDir, sha: headSha(repoDir), path: "foo.txt" }),
+    ).toMatchObject({
+      isNew: false,
+      isDeleted: true,
+      additions: 0,
+      deletions: 1,
+    });
+  });
+
+  it("preserves a rename introduced by a merge against its first parent", async () => {
+    const repoDir = initRepo();
+    commitFile(repoDir, "old.txt", "same\n", "initial");
+    git(["checkout", "-b", "feature"], repoDir);
+    git(["mv", "old.txt", "new.txt"], repoDir);
+    git(["-c", "commit.gpgsign=false", "commit", "-m", "rename"], repoDir);
+    git(["checkout", "main"], repoDir);
+    commitFile(repoDir, "main.txt", "main\n", "advance main");
+    git(["merge", "--no-ff", "feature", "-m", "merge feature"], repoDir);
+    expect(
+      await getCommitFileDiff({ cwd: repoDir, sha: headSha(repoDir), path: "new.txt" }),
+    ).toMatchObject({
+      path: "new.txt",
+      isNew: false,
+      isDeleted: false,
+      additions: 0,
+      deletions: 0,
+      hunks: [],
+    });
+  });
+
  it("returns a merge commit diff against its first parent", async () => {
    const repoDir = initRepo();
    commitFile(repoDir, "README.md", "base\n", "initial");