feat: surface git's color-moved highlights for moved lines

moved code in a diff is highlighted distinctly from added/removed.
Loads the relevant git config keys, threads a 'moved' lane through
the diff renderer, and renders moved-from / moved-to lines with the
configured palette.

Fixes #261

Author: mvanhorn

src/core/config.test.ts

@@ -59,6 +59,7 @@ describe("config resolution", () => {
         'theme = "graphite"',
         "line_numbers = false",
         "transparentBackground = true",
+        "color_moved = true",
         "",
         "[patch]",
         'mode = "split"',
@@ -89,6 +90,7 @@ describe("config resolution", () => {
       hunkHeaders: false,
       agentNotes: true,
       transparentBackground: true,
+      colorMoved: true,
     });
   });
 

src/core/config.ts

@@ -35,6 +35,8 @@ const CUSTOM_THEME_COLOR_KEYS = [
   "muted",
   "addedBg",
   "removedBg",
+  "movedAddedBg",
+  "movedRemovedBg",
   "contextBg",
   "addedContentBg",
   "removedContentBg",
@@ -239,6 +241,7 @@ function readConfigPreferences(source: Record<string, unknown>): CommonOptions {
     transparentBackground:
       normalizeBoolean(source.transparentBackground) ??
       normalizeBoolean(source.transparent_background),
+    colorMoved: normalizeBoolean(source.color_moved),
   };
 }
 
@@ -259,6 +262,7 @@ function mergeOptions(base: CommonOptions, overrides: CommonOptions): CommonOpti
     agentNotes: overrides.agentNotes ?? base.agentNotes,
     copyDecorations: overrides.copyDecorations ?? base.copyDecorations,
     transparentBackground: overrides.transparentBackground ?? base.transparentBackground,
+    colorMoved: overrides.colorMoved ?? base.colorMoved,
   };
 }
 
@@ -353,6 +357,7 @@ export function resolveConfiguredCliInput(
     agentNotes: resolvedOptions.agentNotes ?? DEFAULT_VIEW_PREFERENCES.showAgentNotes,
     copyDecorations: resolvedOptions.copyDecorations ?? DEFAULT_VIEW_PREFERENCES.copyDecorations,
     transparentBackground: resolvedOptions.transparentBackground ?? false,
+    colorMoved: resolvedOptions.colorMoved,
   };
 
   if (resolvedOptions.theme === "custom" && !resolvedCustomTheme) {

src/core/diffFile.ts

@@ -3,7 +3,7 @@ import { findAgentFileContext } from "./agent";
 import { patchLooksBinary } from "./binary";
 import { normalizeDiffMetadataPaths, normalizeDiffPath } from "./diffPaths";
 import type { FileSourceFetcher } from "./fileSource";
-import type { AgentContext, DiffFile } from "./types";
+import type { AgentContext, DiffFile, DiffLineMoveKinds } from "./types";
 
 /** Count visible additions and deletions from parsed diff metadata. */
 export function countDiffStats(metadata: FileDiffMetadata) {
@@ -38,6 +38,7 @@ export interface BuildDiffFileOptions {
   isTooLarge?: boolean;
   stats?: DiffFile["stats"];
   statsTruncated?: boolean;
+  lineMoveKinds?: DiffLineMoveKinds;
 }
 
 /** Build the normalized per-file model used by the UI regardless of input mode. */
@@ -55,6 +56,7 @@ export function buildDiffFile(
     isTooLarge,
     stats,
     statsTruncated,
+    lineMoveKinds,
   }: BuildDiffFileOptions = {},
 ): DiffFile {
   const normalizedMetadata = normalizeDiffMetadataPaths(metadata);
@@ -77,6 +79,7 @@ export function buildDiffFile(
     language: getFiletypeFromFileName(path) ?? undefined,
     stats: stats ?? countDiffStats(normalizedMetadata),
     metadata: normalizedMetadata,
+    lineMoveKinds,
     agent: findAgentFileContext(agentContext, path, resolvedPreviousPath),
     isUntracked,
     isBinary: resolvedIsBinary,

src/core/git.test.ts

@@ -2,7 +2,12 @@ import { afterEach, describe, expect, test } from "bun:test";
 import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
-import { buildGitStashShowArgs, resolveGitDiffEndpoints, runGitText } from "./git";
+import {
+  buildGitDiffArgs,
+  buildGitStashShowArgs,
+  resolveGitDiffEndpoints,
+  runGitText,
+} from "./git";
 import type { VcsCommandInput } from "./types";
 
 const tempDirs: string[] = [];
@@ -51,6 +56,25 @@ afterEach(() => {
   }
 });
 describe("git command helpers", () => {
+  test("enables deterministic color-moved output for patch parsing", () => {
+    const args = buildGitDiffArgs(
+      {
+        kind: "vcs",
+        staged: false,
+        options: { mode: "auto" },
+      },
+      [],
+      { mode: "zebra", whitespaceMode: "allow-indentation-change" },
+    );
+
+    expect(args).toContain("--color=always");
+    expect(args).toContain("--color-moved=zebra");
+    expect(args).toContain("--color-moved-ws=allow-indentation-change");
+    expect(args).not.toContain("--no-color");
+    expect(args).toContain("color.diff.oldMoved=magenta bold");
+    expect(args).toContain("color.diff.newMoved=cyan bold");
+  });
+
   test("disables external diff tools for stash patches", () => {
     const args = buildGitStashShowArgs({
       kind: "stash-show",

src/core/git.ts

@@ -23,6 +23,11 @@ interface RunGitCommandOptions extends RunGitTextOptions {
   acceptedExitCodes?: number[];
 }
 
+export interface GitColorMovedOptions {
+  mode: string;
+  whitespaceMode?: string;
+}
+
 /** Append Git pathspec arguments only when the caller requested them. */
 export function appendGitPathspecs(args: string[], pathspecs?: string[]) {
   if (!pathspecs || pathspecs.length === 0) {
@@ -46,13 +51,58 @@ const DIFF_PREFIX_NORMALIZATION_ARGS = [
   "diff.dstPrefix=b/",
 ];
 
+const GIT_MOVED_LINE_COLOR_CONFIG = [
+  "-c",
+  "color.diff.oldMoved=magenta bold",
+  "-c",
+  "color.diff.oldMovedAlternative=magenta bold",
+  "-c",
+  "color.diff.oldMovedDimmed=magenta dim",
+  "-c",
+  "color.diff.oldMovedAlternativeDimmed=magenta dim",
+  "-c",
+  "color.diff.newMoved=cyan bold",
+  "-c",
+  "color.diff.newMovedAlternative=cyan bold",
+  "-c",
+  "color.diff.newMovedDimmed=cyan dim",
+  "-c",
+  "color.diff.newMovedAlternativeDimmed=cyan dim",
+];
+
 function withNormalizedDiffPrefixes(args: string[]) {
   return [...DIFF_PREFIX_NORMALIZATION_ARGS, ...args];
 }
 
+/** Return Git color flags for patch commands, enabling ANSI only when Hunk needs move classes. */
+function gitPatchColorArgs(colorMoved: GitColorMovedOptions | null) {
+  if (!colorMoved) {
+    return ["--no-color"];
+  }
+
+  return [
+    "--color=always",
+    `--color-moved=${colorMoved.mode}`,
+    ...(colorMoved.whitespaceMode ? [`--color-moved-ws=${colorMoved.whitespaceMode}`] : []),
+  ];
+}
+
+/** Add deterministic moved-line colors so the parser can classify Git's ANSI output reliably. */
+function withGitMovedLineColorConfig(args: string[], colorMoved: GitColorMovedOptions | null) {
+  if (!colorMoved) {
+    return args;
+  }
+
+  return [...GIT_MOVED_LINE_COLOR_CONFIG, ...args];
+}
+
 /** Build the exact `git diff` arguments used for the shared working-tree and range review path. */
-export function buildGitDiffArgs(input: VcsCommandInput, excludedPathspecs: string[] = []) {
-  const args = ["diff", "--no-ext-diff", "--find-renames", "--no-color"];
+export function buildGitDiffArgs(
+  input: VcsCommandInput,
+  excludedPathspecs: string[] = [],
+  colorMoved: GitColorMovedOptions | null = null,
+) {
+  const args = ["diff", "--no-ext-diff", "--find-renames", ...gitPatchColorArgs(colorMoved)];
 
   if (input.staged) {
     args.push("--staged");
@@ -72,7 +122,7 @@ export function buildGitDiffArgs(input: VcsCommandInput, excludedPathspecs: stri
     appendGitPathspecs(args, input.pathspecs);
   }
 
-  return withNormalizedDiffPrefixes(args);
+  return withNormalizedDiffPrefixes(withGitMovedLineColorConfig(args, colorMoved));
 }
 
 /** Build the cheap tracked-file stats query used to skip huge file diffs before patch output. */
@@ -115,26 +165,45 @@ function buildGitNewFileDiffArgs(filePath: string) {
 }
 
 /** Build the exact `git show` arguments used for commit review. */
-export function buildGitShowArgs(input: ShowCommandInput) {
-  const args = ["show", "--format=", "--no-ext-diff", "--find-renames", "--no-color"];
+export function buildGitShowArgs(
+  input: ShowCommandInput,
+  colorMoved: GitColorMovedOptions | null = null,
+) {
+  const args = [
+    "show",
+    "--format=",
+    "--no-ext-diff",
+    "--find-renames",
+    ...gitPatchColorArgs(colorMoved),
+  ];
 
   if (input.ref) {
     args.push(input.ref);
   }
 
   appendGitPathspecs(args, input.pathspecs);
-  return withNormalizedDiffPrefixes(args);
+  return withNormalizedDiffPrefixes(withGitMovedLineColorConfig(args, colorMoved));
 }
 
 /** Build the exact `git stash show -p` arguments used for stash review. */
-export function buildGitStashShowArgs(input: StashShowCommandInput) {
-  const args = ["stash", "show", "-p", "--no-ext-diff", "--find-renames", "--no-color"];
+export function buildGitStashShowArgs(
+  input: StashShowCommandInput,
+  colorMoved: GitColorMovedOptions | null = null,
+) {
+  const args = [
+    "stash",
+    "show",
+    "-p",
+    "--no-ext-diff",
+    "--find-renames",
+    ...gitPatchColorArgs(colorMoved),
+  ];
 
   if (input.ref) {
     args.push(input.ref);
   }
 
-  return withNormalizedDiffPrefixes(args);
+  return withNormalizedDiffPrefixes(withGitMovedLineColorConfig(args, colorMoved));
 }
 
 export function formatGitCommandLabel(input: GitBackedInput) {
@@ -330,6 +399,72 @@ export function runGitText(options: RunGitTextOptions) {
   return runGitCommand(options).stdout;
 }
 
+const GIT_BOOLEAN_TRUE_VALUES = new Set(["true", "yes", "on", "1", "always"]);
+const GIT_BOOLEAN_FALSE_VALUES = new Set(["false", "no", "off", "0", "never"]);
+
+/** Read an optional Git config value without treating an unset key as an error. */
+function readOptionalGitConfig(
+  input: GitBackedInput,
+  key: string,
+  options: Omit<RunGitTextOptions, "input" | "args"> = {},
+) {
+  const result = runGitCommand({
+    input,
+    args: ["config", "--get", key],
+    ...options,
+    acceptedExitCodes: [0, 1],
+  });
+
+  if (result.exitCode !== 0) {
+    return undefined;
+  }
+
+  return result.stdout.trim() || undefined;
+}
+
+/** Normalize Git's diff.colorMoved config into the mode Hunk should request from Git. */
+function normalizeGitColorMovedMode(value: string | undefined) {
+  if (!value) {
+    return undefined;
+  }
+
+  const normalized = value.toLowerCase();
+  if (GIT_BOOLEAN_FALSE_VALUES.has(normalized) || normalized === "no") {
+    return null;
+  }
+
+  if (GIT_BOOLEAN_TRUE_VALUES.has(normalized)) {
+    return "zebra";
+  }
+
+  return value;
+}
+
+/** Resolve whether Hunk should ask Git to color moved lines for this patch command. */
+export function resolveGitColorMovedOptions(
+  input: GitBackedInput,
+  options: Omit<RunGitTextOptions, "input" | "args"> = {},
+): GitColorMovedOptions | null {
+  const gitMode = normalizeGitColorMovedMode(
+    readOptionalGitConfig(input, "diff.colorMoved", options),
+  );
+
+  if (gitMode === null) {
+    return null;
+  }
+
+  const mode = gitMode ?? (input.options.colorMoved ? "zebra" : undefined);
+  if (!mode) {
+    return null;
+  }
+
+  const whitespaceMode = readOptionalGitConfig(input, "diff.colorMovedWS", options);
+  return {
+    mode,
+    whitespaceMode,
+  };
+}
+
 /**
  * Return whether one `hunk diff` input still compares against the live working tree.
  *

src/core/loaders.test.ts

@@ -706,6 +706,62 @@ describe("loadAppBootstrap", () => {
     ]);
   });
 
+  test("tags moved lines from git diff.colorMoved output", async () => {
+    const dir = createTempRepo("hunk-git-color-moved-");
+
+    writeFileSync(
+      join(dir, "example.txt"),
+      [
+        "start anchor",
+        "relocated block first line has many chars",
+        "relocated block second line has many chars",
+        "relocated block third line has many chars",
+        "middle unchanged one has many chars",
+        "middle unchanged two has many chars",
+        "end anchor",
+        "",
+      ].join("\n"),
+    );
+    git(dir, "add", "example.txt");
+    git(dir, "commit", "-m", "initial");
+    git(dir, "config", "--local", "diff.colorMoved", "zebra");
+
+    writeFileSync(
+      join(dir, "example.txt"),
+      [
+        "start anchor",
+        "middle unchanged one has many chars",
+        "middle unchanged two has many chars",
+        "relocated block first line has many chars",
+        "relocated block second line has many chars",
+        "relocated block third line has many chars",
+        "end anchor",
+        "",
+      ].join("\n"),
+    );
+
+    const bootstrap = await loadFromRepo(dir, {
+      kind: "vcs",
+      staged: false,
+      options: { mode: "auto" },
+    });
+    const file = bootstrap.changeset.files[0];
+
+    expect(file?.path).toBe("example.txt");
+    expect(file?.lineMoveKinds?.additionLines.some(Boolean)).toBe(true);
+    expect(file?.lineMoveKinds?.deletionLines.some(Boolean)).toBe(true);
+
+    const movedAdditions = file?.metadata.additionLines.filter(
+      (_line, index) => file.lineMoveKinds?.additionLines[index] === "moved",
+    );
+    const movedDeletions = file?.metadata.deletionLines.filter(
+      (_line, index) => file.lineMoveKinds?.deletionLines[index] === "moved",
+    );
+
+    expect(movedAdditions).toContain("middle unchanged one has many chars\n");
+    expect(movedDeletions).toContain("middle unchanged one has many chars\n");
+  });
+
   test("reports a friendly error when git review runs outside a repository", async () => {
     const dir = mkdtempSync(join(tmpdir(), "hunk-nonrepo-"));
     tempDirs.push(dir);