refactor: map VCS providers by operation

.changeset/ninety-friends-count.md

@@ -0,0 +1,4 @@
+---
+---
+
+Refactor VCS adapter dispatch to use operation maps without a release note.

src/core/config.ts

@@ -1,7 +1,7 @@
 import fs from "node:fs";
 import { join } from "node:path";
 import { resolveGlobalConfigPath } from "./paths";
-import { detectVcs, findVcsRepoRootCandidate, isVcsId } from "./vcs";
+import { detectVcs, findVcsRepoRootCandidate, getDefaultVcsAdapter, isVcsId } from "./vcs";
 import type {
   CliInput,
   CommonOptions,
@@ -285,7 +285,7 @@ function resolveConfigLayer(source: Record<string, unknown>, input: CliInput): C
 
 /** Choose the VCS backend that best matches the discovered checkout. */
 function detectRepoVcsMode(cwd: string): VcsMode {
-  return detectVcs(cwd)?.id ?? "git";
+  return detectVcs(cwd)?.id ?? getDefaultVcsAdapter().id;
 }
 
 /** Parse one TOML config file into a plain object. */
@@ -349,7 +349,7 @@ export function resolveConfiguredCliInput(
     pager: input.options.pager ?? false,
     watch: input.options.watch ?? resolvedOptions.watch ?? false,
     excludeUntracked: resolvedOptions.excludeUntracked ?? false,
-    vcs: resolvedOptions.vcs ?? "git",
+    vcs: resolvedOptions.vcs ?? getDefaultVcsAdapter().id,
     mode: resolvedOptions.mode ?? DEFAULT_VIEW_PREFERENCES.mode,
     lineNumbers: resolvedOptions.lineNumbers ?? DEFAULT_VIEW_PREFERENCES.showLineNumbers,
     wrapLines: resolvedOptions.wrapLines ?? DEFAULT_VIEW_PREFERENCES.wrapLines,

src/core/fileSource.test.ts

@@ -3,6 +3,7 @@ import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { createFileSourceFetcher, SourceTextTooLargeError } from "./fileSource";
+import { createGitFileSourceFetcher } from "./vcs/gitSource";
 
 const tempDirs: string[] = [];
 
@@ -127,7 +128,7 @@ describe("createFileSourceFetcher", () => {
     git(repoRoot, "add", ".");
     git(repoRoot, "commit", "-m", "second");
 
-    const fetcher = createFileSourceFetcher({
+    const fetcher = createGitFileSourceFetcher({
       old: { kind: "git-blob", repoRoot, ref: "HEAD~1", path: filePath },
       new: { kind: "git-blob", repoRoot, ref: "HEAD", path: filePath },
     });
@@ -147,7 +148,7 @@ describe("createFileSourceFetcher", () => {
     git(repoRoot, "add", filePath);
     writeFileSync(join(repoRoot, filePath), "working tree\n");
 
-    const fetcher = createFileSourceFetcher({
+    const fetcher = createGitFileSourceFetcher({
       old: { kind: "git-index", repoRoot, path: filePath },
       new: { kind: "fs", absolutePath: join(repoRoot, filePath) },
     });
@@ -166,7 +167,7 @@ describe("createFileSourceFetcher", () => {
     writeFileSync(join(repoRoot, filePath), "staged source\n");
     git(repoRoot, "add", filePath);
 
-    const fetcher = createFileSourceFetcher(
+    const fetcher = createGitFileSourceFetcher(
       {
         old: { kind: "git-blob", repoRoot, ref: "HEAD", path: filePath },
         new: { kind: "git-index", repoRoot, path: filePath },
@@ -197,7 +198,7 @@ describe("createFileSourceFetcher", () => {
       )) as typeof Bun.spawn;
 
     try {
-      const fetcher = createFileSourceFetcher({
+      const fetcher = createGitFileSourceFetcher({
         old: { kind: "git-blob", repoRoot: process.cwd(), ref: "HEAD", path: "note.txt" },
         new: { kind: "none" },
       });
@@ -235,7 +236,7 @@ describe("createFileSourceFetcher", () => {
     }) as typeof Bun.spawn;
 
     try {
-      const fetcher = createFileSourceFetcher(
+      const fetcher = createGitFileSourceFetcher(
         {
           old: { kind: "git-blob", repoRoot: process.cwd(), ref: "HEAD", path: "note.txt" },
           new: { kind: "git-index", repoRoot: process.cwd(), path: "note.txt" },
@@ -261,7 +262,7 @@ describe("createFileSourceFetcher", () => {
     git(repoRoot, "add", ".");
     git(repoRoot, "commit", "-m", "first");
 
-    const fetcher = createFileSourceFetcher({
+    const fetcher = createGitFileSourceFetcher({
       old: { kind: "git-blob", repoRoot, ref: "HEAD", path: "missing-from-history.txt" },
       new: { kind: "none" },
     });
@@ -274,7 +275,7 @@ describe("createFileSourceFetcher", () => {
 
   test("logs unexpected git source failures with object context", async () => {
     const repoRoot = createTempDir("hunk-source-git-not-repo-");
-    const fetcher = createFileSourceFetcher({
+    const fetcher = createGitFileSourceFetcher({
       old: { kind: "git-blob", repoRoot, ref: "HEAD", path: "note.txt" },
       new: { kind: "none" },
     });

src/core/fileSource.ts

@@ -1,26 +1,22 @@
 /**
- * Low-level readers for full file contents used by input and VCS adapters.
+ * Generic full-file source fetcher primitives used by input loaders and VCS adapters.
  *
  * Each `DiffFile` may carry a `FileSourceFetcher` that knows how to read the
- * file's "old" and "new" sides without re-running the original diff. VCS
- * adapters own VCS-specific source-spec construction; this module only executes
- * the concrete reads and returns `null` when source content is unreachable.
+ * file's "old" and "new" sides without re-running the original diff. Provider-
+ * specific object reads live beside their VCS adapters; this module only owns
+ * provider-neutral fetcher contracts and filesystem reads.
  */
 
-export type FileSourceSpec =
-  | { kind: "none" }
-  | { kind: "fs"; absolutePath: string }
-  | { kind: "git-blob"; repoRoot: string; ref: string; path: string }
-  | { kind: "git-index"; repoRoot: string; path: string };
+export type FileSourceSpec = { kind: "none" } | { kind: "fs"; absolutePath: string };
 
 export type FileSourceSide = "old" | "new";
 
 export interface FileSourceFetcher {
   /**
    * Returns the file's full source text on the requested side, or `null` when
-   * the side is not reachable (deleted side, missing path, git error). Built-in
-   * fetchers resolve `null` instead of rejecting, but UI callers still handle
-   * custom fetcher rejection defensively.
+   * the side is not reachable (deleted side, missing path, provider error).
+   * Built-in fetchers resolve `null` instead of rejecting, but UI callers still
+   * handle custom fetcher rejection defensively.
    */
   getFullText(side: FileSourceSide): Promise<string | null>;
 }
@@ -36,7 +32,6 @@ export class SourceTextTooLargeError extends Error {
 }
 
 export interface FileSourceFetcherOptions {
-  gitExecutable?: string;
   maxSourceBytes?: number;
 }
 
@@ -54,7 +49,7 @@ function firstDiagnosticLine(text: string) {
 }
 
 /** Keep source-load diagnostics terse enough to be useful in logs. */
-function logSourceDiagnostic(message: string, detail?: unknown) {
+export function logSourceDiagnostic(message: string, detail?: unknown) {
   if (detail instanceof Error) {
     console.error(`hunk: ${message}: ${detail.message}`, detail);
     return;
@@ -64,18 +59,6 @@ function logSourceDiagnostic(message: string, detail?: unknown) {
   console.error(detailText ? `hunk: ${message}: ${detailText}` : `hunk: ${message}`);
 }
 
-/** Return whether a Git failure is an expected missing source side/path. */
-function isExpectedMissingGitSource(stderr: string) {
-  const normalized = stderr.toLowerCase();
-  return [
-    "exists on disk, but not in",
-    "does not exist in",
-    "invalid object name",
-    "needed a single revision",
-    "unknown revision or path not in the working tree",
-  ].some((fragment) => normalized.includes(fragment));
-}
-
 async function readFsSpec(
   spec: Extract<FileSourceSpec, { kind: "fs" }>,
   maxSourceBytes: number,
@@ -101,28 +84,7 @@ async function readFsSpec(
   }
 }
 
-function readGitBlobSpec(
-  spec: Extract<FileSourceSpec, { kind: "git-blob" }>,
-  gitExecutable = "git",
-  maxSourceBytes: number,
-): Promise<string | null> {
-  return readGitObjectSpec(
-    spec.repoRoot,
-    `${spec.ref}:${spec.path}`,
-    gitExecutable,
-    maxSourceBytes,
-  );
-}
-
-function readGitIndexSpec(
-  spec: Extract<FileSourceSpec, { kind: "git-index" }>,
-  gitExecutable = "git",
-  maxSourceBytes: number,
-): Promise<string | null> {
-  return readGitObjectSpec(spec.repoRoot, `:${spec.path}`, gitExecutable, maxSourceBytes);
-}
-
-async function readStreamTextWithLimit(
+export async function readStreamTextWithLimit(
   stream: ReadableStream<Uint8Array> | null,
   maxBytes: number,
   onTooLarge?: () => void,
@@ -163,91 +125,21 @@ async function readStreamTextWithLimit(
   return new TextDecoder().decode(combined);
 }
 
-/** Read a blob-like Git object spec such as `HEAD:path` or `:path`. */
-async function readGitObjectSpec(
-  repoRoot: string,
-  objectName: string,
-  gitExecutable = "git",
-  maxSourceBytes: number,
-): Promise<string | null> {
-  let proc: Bun.ReadableSubprocess;
-
-  try {
-    proc = Bun.spawn([gitExecutable, "show", objectName], {
-      cwd: repoRoot,
-      stdin: "ignore",
-      stdout: "pipe",
-      stderr: "pipe",
-    });
-  } catch (error) {
-    logSourceDiagnostic(`failed to run Git while reading source ${objectName}`, error);
-    return null;
-  }
-
-  let output: [number, string, string];
-  try {
-    output = await Promise.all([
-      proc.exited,
-      readStreamTextWithLimit(proc.stdout, maxSourceBytes, () => proc.kill()),
-      readStreamTextWithLimit(
-        proc.stderr,
-        64 * 1024,
-        undefined,
-        (maxBytes) => new Error(`Git source diagnostics exceeded ${maxBytes} bytes.`),
-      ),
-    ]);
-  } catch (error) {
-    if (error instanceof SourceTextTooLargeError) {
-      proc.kill();
-      await proc.exited.catch(() => undefined);
-      throw error;
-    }
-
-    logSourceDiagnostic(`failed to collect Git source ${objectName}`, error);
-    return null;
-  }
-
-  const [exitCode, stdout, stderr] = output;
-
-  if (exitCode !== 0) {
-    if (!isExpectedMissingGitSource(stderr)) {
-      logSourceDiagnostic(`failed to read Git source ${objectName} in ${repoRoot}`, stderr);
-    }
-    return null;
-  }
-
-  return stdout;
-}
-
 async function readSpec(
   spec: FileSourceSpec,
-  {
-    gitExecutable = "git",
-    maxSourceBytes = DEFAULT_SOURCE_TEXT_MAX_BYTES,
-  }: FileSourceFetcherOptions = {},
+  { maxSourceBytes = DEFAULT_SOURCE_TEXT_MAX_BYTES }: FileSourceFetcherOptions = {},
 ): Promise<string | null> {
   if (spec.kind === "none") {
     return null;
   }
 
-  if (spec.kind === "fs") {
-    return readFsSpec(spec, maxSourceBytes);
-  }
-
-  if (spec.kind === "git-index") {
-    return readGitIndexSpec(spec, gitExecutable, maxSourceBytes);
-  }
-
-  return readGitBlobSpec(spec, gitExecutable, maxSourceBytes);
+  return readFsSpec(spec, maxSourceBytes);
 }
 
 /** Build a per-file source fetcher that caches each side's resolved text. */
 export function createFileSourceFetcher(
   specs: ResolvedSpecs,
-  {
-    gitExecutable = "git",
-    maxSourceBytes = DEFAULT_SOURCE_TEXT_MAX_BYTES,
-  }: Readonly<FileSourceFetcherOptions> = {},
+  { maxSourceBytes = DEFAULT_SOURCE_TEXT_MAX_BYTES }: Readonly<FileSourceFetcherOptions> = {},
 ): FileSourceFetcher {
   const cache = new Map<FileSourceSide, string | null>();
 
@@ -257,7 +149,7 @@ export function createFileSourceFetcher(
         return cache.get(side) ?? null;
       }
 
-      const text = await readSpec(specs[side], { gitExecutable, maxSourceBytes });
+      const text = await readSpec(specs[side], { maxSourceBytes });
       cache.set(side, text);
       return text;
     },

src/core/git.test.ts

@@ -9,7 +9,7 @@ import {
   resolveGitDiffEndpoints,
   runGitText,
 } from "./git";
-import type { VcsCommandInput } from "./types";
+import type { VcsDiffCommandInput } from "./types";
 
 const tempDirs: string[] = [];
 
@@ -39,7 +39,7 @@ function createTempRepo(prefix: string) {
   return dir;
 }
 
-function makeGitInput(overrides: Partial<VcsCommandInput> = {}): VcsCommandInput {
+function makeGitInput(overrides: Partial<VcsDiffCommandInput> = {}): VcsDiffCommandInput {
   return {
     kind: "vcs",
     staged: false,