fix(server): preserve staging during commit message generation

apps/server/src/git/GitManager.test.ts

@@ -3116,6 +3116,53 @@ it.layer(GitManagerTestLayer)("GitManager", (it) => {
     }),
   );
 
+  it.effect.each([undefined, ["README.md"]])(
+    "a failed generation preserves staging changed while generating (paths: %s)",
+    (filePaths) =>
+      Effect.gen(function* () {
+        const repoDir = yield* makeTempDir("t3code-git-manager-");
+        yield* initRepo(repoDir);
+        NodeFS.writeFileSync(NodePath.join(repoDir, "README.md"), "hello\nstaged\n");
+        yield* runGit(repoDir, ["add", "README.md"]);
+        NodeFS.appendFileSync(NodePath.join(repoDir, "README.md"), "unstaged\n");
+        NodeFS.writeFileSync(NodePath.join(repoDir, "untracked.txt"), "untracked\n");
+        const indexBefore = NodeFS.readFileSync(NodePath.join(repoDir, ".git/index"));
+        const headBefore = (yield* runGit(repoDir, ["rev-parse", "HEAD"])).stdout;
+        const gitDriver = yield* GitVcsDriver.GitVcsDriver;
+        let indexDuring: Buffer | undefined;
+        let indexAfterUserStage: Buffer | undefined;
+        const { manager } = yield* makeManager({
+          textGeneration: {
+            generateCommitMessage: () =>
+              Effect.gen(function* () {
+                indexDuring = NodeFS.readFileSync(NodePath.join(repoDir, ".git/index"));
+                yield* runGit(repoDir, ["add", "untracked.txt"]).pipe(
+                  Effect.provideService(GitVcsDriver.GitVcsDriver, gitDriver),
+                  Effect.orDie,
+                );
+                indexAfterUserStage = NodeFS.readFileSync(NodePath.join(repoDir, ".git/index"));
+                return yield* new TextGenerationError({
+                  operation: "generateCommitMessage",
+                  detail: "Provider rejected generation",
+                });
+              }),
+          },
+        });
+        const result = yield* runStackedAction(manager, {
+          cwd: repoDir,
+          action: "commit",
+          ...(filePaths ? { filePaths } : {}),
+        }).pipe(Effect.result);
+        expect(Result.isFailure(result)).toBe(true);
+        expect(indexDuring).toEqual(indexBefore);
+        expect(NodeFS.readFileSync(NodePath.join(repoDir, ".git/index"))).toEqual(
+          indexAfterUserStage,
+        );
+        expect((yield* runGit(repoDir, ["rev-parse", "HEAD"])).stdout).toBe(headBefore);
+        expect((yield* runGit(repoDir, ["diff"])).stdout).toContain("+unstaged");
+      }),
+  );
+
   it.effect("uses custom commit message when provided", () =>
     Effect.gen(function* () {
       const repoDir = yield* makeTempDir("t3code-git-manager-");

apps/server/src/git/GitManager.ts

@@ -1985,6 +1985,7 @@ export const make = Effect.gen(function* () {
         : null;
     const { commitSha } = yield* gitCore.commit(cwd, suggestion.subject, suggestion.body, {
       timeoutMs: COMMIT_TIMEOUT_MS,
+      stage: filePaths ? { filePaths } : {},
       ...(commitProgress ? { progress: commitProgress } : {}),
     });
     if (currentHookName !== null) {

apps/server/src/vcs/GitVcsDriver.ts

@@ -174,6 +174,8 @@ export interface GitCommitProgress {
 export interface GitCommitOptions {
   readonly timeoutMs?: number;
   readonly progress?: GitCommitProgress;
+  /** Stage the current working tree immediately before committing. */
+  readonly stage?: { readonly filePaths?: readonly string[] };
 }
 
 export interface GitDeleteLocalBranchInput {

apps/server/src/vcs/GitVcsDriverCore.test.ts

@@ -3052,7 +3052,7 @@ it.layer(TestLayer)("GitVcsDriver core integration", (it) => {
   });
 
   describe("commit context", () => {
-    it.effect("stages selected files and commits only those files", () =>
+    it.effect("prepares selected files without staging and commits only those files", () =>
       Effect.gen(function* () {
         const cwd = yield* makeTmpDir();
         yield* initRepoWithCommit(cwd);
@@ -3064,8 +3064,9 @@ it.layer(TestLayer)("GitVcsDriver core integration", (it) => {
         const context = yield* driver.prepareCommitContext(cwd, ["a.txt"]);
         assert.include(context?.stagedSummary ?? "", "a.txt");
         assert.notInclude(context?.stagedSummary ?? "", "b.txt");
+        assert.equal(yield* git(cwd, ["diff", "--cached", "--name-only"]), "");
 
-        const commit = yield* driver.commit(cwd, "Add a", "");
+        const commit = yield* driver.commit(cwd, "Add a", "", { stage: { filePaths: ["a.txt"] } });
         assert.match(commit.commitSha, /^[a-f0-9]{40}$/);
         assert.equal(yield* git(cwd, ["log", "-1", "--pretty=%s"]), "Add a");
 
@@ -3084,14 +3085,96 @@ it.layer(TestLayer)("GitVcsDriver core integration", (it) => {
         yield* writeTextFile(cwd, "selected[1].txt", "literal\n");
         yield* writeTextFile(cwd, "selected1.txt", "pattern match\n");
 
-        yield* driver.prepareCommitContext(cwd, ["selected[1].txt"]);
+        const context = yield* driver.prepareCommitContext(cwd, ["selected[1].txt"]);
 
-        assert.equal(yield* git(cwd, ["diff", "--cached", "--name-only"]), "selected[1].txt");
+        assert.include(context?.stagedSummary ?? "", "selected[1].txt");
+        assert.notInclude(context?.stagedSummary ?? "", "selected1.txt");
+        assert.equal(yield* git(cwd, ["diff", "--cached", "--name-only"]), "");
+        yield* driver.commit(cwd, "Add literal path", "", {
+          stage: { filePaths: ["selected[1].txt"] },
+        });
+        assert.equal(
+          yield* git(cwd, ["show", "--pretty=", "--name-only", "HEAD"]),
+          "selected[1].txt",
+        );
 
         const status = yield* git(cwd, ["status", "--porcelain"]);
         assert.include(status, "?? selected1.txt");
       }),
     );
+
+    it.effect.each([false, true])(
+      "preserves partial staging and split-index files (split: %s)",
+      (split) =>
+        Effect.gen(function* () {
+          const cwd = yield* makeTmpDir();
+          yield* initRepoWithCommit(cwd);
+          if (split) yield* git(cwd, ["config", "core.splitIndex", "true"]);
+          yield* writeTextFile(cwd, "README.md", "# test\nstaged\n");
+          yield* git(cwd, ["add", "README.md"]);
+          yield* writeTextFile(cwd, "README.md", "# test\nstaged\nunstaged\n");
+          yield* writeTextFile(cwd, "untracked.txt", "untracked\n");
+          yield* writeTextFile(cwd, ".gitignore", "ignored.txt\n");
+          yield* writeTextFile(cwd, "ignored.txt", "ignored\n");
+          const before = NodeFS.readFileSync(`${cwd}/.git/index`);
+          const shared = NodeFS.readdirSync(`${cwd}/.git`).filter((name) =>
+            name.startsWith("sharedindex."),
+          );
+          const driver = yield* GitVcsDriver.GitVcsDriver;
+          for (const paths of [undefined, ["README.md"]]) {
+            const context = yield* driver.prepareCommitContext(cwd, paths);
+            assert.include(context?.stagedPatch ?? "", "unstaged");
+            assert.notInclude(context?.stagedSummary ?? "", "ignored.txt");
+            assert.deepEqual(NodeFS.readFileSync(`${cwd}/.git/index`), before);
+            assert.deepEqual(
+              NodeFS.readdirSync(`${cwd}/.git`).filter((name) => name.startsWith("sharedindex.")),
+              shared,
+            );
+          }
+        }),
+    );
+
+    it.effect("prepares an unborn repository without creating a real index", () =>
+      Effect.gen(function* () {
+        const cwd = yield* makeTmpDir();
+        const driver = yield* GitVcsDriver.GitVcsDriver;
+        yield* driver.initRepo({ cwd });
+        yield* git(cwd, ["config", "user.email", "test@test.com"]);
+        yield* git(cwd, ["config", "user.name", "Test"]);
+        yield* writeTextFile(cwd, "initial.txt", "initial\n");
+        for (const paths of [undefined, ["initial.txt"]]) {
+          const context = yield* driver.prepareCommitContext(cwd, paths);
+          assert.include(context?.stagedSummary ?? "", "initial.txt");
+          assert.isFalse(NodeFS.existsSync(`${cwd}/.git/index`));
+        }
+        yield* driver.commit(cwd, "Initial", "", { stage: { filePaths: ["initial.txt"] } });
+        assert.equal(yield* git(cwd, ["show", "HEAD:initial.txt"]), "initial");
+      }),
+    );
+
+    it.effect("preserves merge metadata while preparing selected and all files", () =>
+      Effect.gen(function* () {
+        const cwd = yield* makeTmpDir();
+        const { initialBranch } = yield* initRepoWithCommit(cwd);
+        yield* git(cwd, ["checkout", "-b", "feature"]);
+        yield* writeTextFile(cwd, "feature.txt", "feature\n");
+        yield* git(cwd, ["add", "."]);
+        yield* git(cwd, ["commit", "-m", "Feature"]);
+        yield* git(cwd, ["checkout", initialBranch]);
+        yield* git(cwd, ["merge", "--no-commit", "--no-ff", "feature"]);
+        yield* writeTextFile(cwd, "README.md", "# test\nmerge edit\n");
+        const names = ["index", "MERGE_HEAD", "MERGE_MSG", "ORIG_HEAD"];
+        const before = names.map((name) => NodeFS.readFileSync(`${cwd}/.git/${name}`));
+        const driver = yield* GitVcsDriver.GitVcsDriver;
+        for (const paths of [undefined, ["README.md"]]) {
+          yield* driver.prepareCommitContext(cwd, paths);
+          assert.deepEqual(
+            names.map((name) => NodeFS.readFileSync(`${cwd}/.git/${name}`)),
+            before,
+          );
+        }
+      }),
+    );
   });
 
   describe("remote operations", () => {
@@ -3271,7 +3354,7 @@ it.layer(TestLayer)("GitVcsDriver core integration", (it) => {
           refName: "feature/push",
         });
         yield* writeTextFile(cwd, "feature.txt", "feature\n");
-        yield* (yield* GitVcsDriver.GitVcsDriver).prepareCommitContext(cwd);
+        yield* git(cwd, ["add", "-A"]);
         yield* (yield* GitVcsDriver.GitVcsDriver).commit(cwd, "Add feature", "");
 
         const pushed = yield* (yield* GitVcsDriver.GitVcsDriver).pushCurrentBranch(cwd, null);
@@ -3343,7 +3426,7 @@ it.layer(TestLayer)("GitVcsDriver core integration", (it) => {
           yield* git(cwd, ["remote", "add", "origin", remote]);
           yield* git(cwd, ["push", "-u", "origin", "main"]);
           yield* writeTextFile(cwd, "upstream.txt", "upstream\n");
-          yield* driver.prepareCommitContext(cwd);
+          yield* git(cwd, ["add", "-A"]);
           yield* driver.commit(cwd, "Add upstream update", "");
 
           const pushed = yield* driver.pushCurrentBranch(cwd, null);
@@ -3384,7 +3467,7 @@ it.layer(TestLayer)("GitVcsDriver core integration", (it) => {
         const devSha = yield* git(cwd, ["rev-parse", "HEAD"]);
         yield* git(cwd, ["checkout", "-b", "feature/x", "origin/dev"]);
         yield* writeTextFile(cwd, "feature.txt", "feature\n");
-        yield* driver.prepareCommitContext(cwd);
+        yield* git(cwd, ["add", "-A"]);
         yield* driver.commit(cwd, "Add feature", "");
 
         const pushed = yield* driver.pushCurrentBranch(cwd, null);
@@ -3418,7 +3501,7 @@ it.layer(TestLayer)("GitVcsDriver core integration", (it) => {
         yield* git(cwd, ["checkout", "-b", "feature/y", "origin/main"]);
         yield* git(cwd, ["config", "branch.feature/y.gh-merge-base", "release/v2"]);
         yield* writeTextFile(cwd, "feature.txt", "feature\n");
-        yield* driver.prepareCommitContext(cwd);
+        yield* git(cwd, ["add", "-A"]);
         yield* driver.commit(cwd, "Add feature", "");
 
         const pushed = yield* driver.pushCurrentBranch(cwd, null);
@@ -3456,7 +3539,7 @@ it.layer(TestLayer)("GitVcsDriver core integration", (it) => {
           "upstream/effect-atom",
         );
         yield* writeTextFile(cwd, "alias.txt", "alias\n");
-        yield* driver.prepareCommitContext(cwd);
+        yield* git(cwd, ["add", "-A"]);
         yield* driver.commit(cwd, "Add alias update", "");
 
         const pushed = yield* driver.pushCurrentBranch(cwd, null);