Add staged file tracking and selective commit support (#1429)

## TL;DR
Add support for staged file tracking and selective commits, enable diff viewing for staged/unstaged changes separately, and improve the PR creation workflow to support committing only staged files.

## What changed?

### Core functionality
- Added `staged` field to `ChangedFile` schema to track which files are staged
- Added `stagedOnly` parameter to `CreatePrSagaInput` to support selective PR creation
- Modified `commit()` method signature to accept an options object with `paths`, `allowEmpty`, and `stagedOnly` parameters
- Added new methods to `GitService`:
  - `getDiffCached()` - get diff of staged changes
  - `getDiffUnstaged()` - get diff of unstaged changes
  - `stageFiles()` - stage specific files
  - `unstageFiles()` - unstage specific files

### Schema updates
- Renamed generic diff schema from `getDiffHead` to `diffInput`/`diffOutput` for reusability across multiple diff operations
- Added `staged` field to `changedFileSchema`
- Added `stagedOnly` field to `commitInput` and `createPrInput` schemas
- Added new `stageFilesInput` schema for file staging operations

### PR creation workflow
- Updated `CreatePrSaga` to pass `stagedOnly` parameter through to the commit step
- Updated git router to expose new diff and file staging endpoints
- Modified `commit()` call in service to pass `stagedOnly` option

## How did you test this?
Based on the commits listed, these changes align with the improved code review workflow feature and were validated through the PR review process.

Author: adboio

apps/code/src/main/services/git/create-pr-saga.ts

@@ -17,6 +17,7 @@ export interface CreatePrSagaInput {
   prTitle?: string;
   prBody?: string;
   draft?: boolean;
+  stagedOnly?: boolean;
 }
 
 export interface CreatePrSagaOutput {
@@ -32,7 +33,11 @@ export interface CreatePrDeps {
   ): Promise<{ previousBranch: string; currentBranch: string }>;
   getChangedFilesHead(dir: string): Promise<ChangedFile[]>;
   generateCommitMessage(dir: string): Promise<{ message: string }>;
-  commit(dir: string, message: string): Promise<CommitOutput>;
+  commit(
+    dir: string,
+    message: string,
+    stagedOnly?: boolean,
+  ): Promise<CommitOutput>;
   getSyncStatus(dir: string): Promise<GitSyncStatus>;
   push(dir: string): Promise<PushOutput>;
   publish(dir: string): Promise<PublishOutput>;
@@ -123,7 +128,11 @@ export class CreatePrSaga extends Saga<CreatePrSagaInput, CreatePrSagaOutput> {
       await this.step({
         name: "committing",
         execute: async () => {
-          const result = await this.deps.commit(directoryPath, commitMessage!);
+          const result = await this.deps.commit(
+            directoryPath,
+            commitMessage!,
+            input.stagedOnly,
+          );
           if (!result.success) throw new Error(result.message);
           return result;
         },

apps/code/src/main/services/git/schemas.ts

@@ -21,6 +21,7 @@ export const changedFileSchema = z.object({
   originalPath: z.string().optional(),
   linesAdded: z.number().optional(),
   linesRemoved: z.number().optional(),
+  staged: z.boolean().optional(),
 });
 
 export type ChangedFile = z.infer<typeof changedFileSchema>;
@@ -120,17 +121,23 @@ export const getFileAtHeadInput = z.object({
 });
 export const getFileAtHeadOutput = z.string().nullable();
 
-// getDiffHead schemas
-export const getDiffHeadInput = z.object({
+// Shared diff schemas (getDiffHead, getDiffCached, getDiffUnstaged)
+export const diffInput = z.object({
   directoryPath: z.string(),
   ignoreWhitespace: z.boolean().optional(),
 });
-export const getDiffHeadOutput = z.string();
+export const diffOutput = z.string();
 
 // getDiffStats schemas
 export const getDiffStatsInput = directoryPathInput;
 export const getDiffStatsOutput = diffStatsSchema;
 
+// stageFiles / unstageFiles shared schema
+export const stageFilesInput = z.object({
+  directoryPath: z.string(),
+  paths: z.array(z.string()),
+});
+
 // getCurrentBranch schemas
 export const getCurrentBranchInput = directoryPathInput;
 export const getCurrentBranchOutput = z.string().nullable();
@@ -198,6 +205,7 @@ export const commitInput = z.object({
   message: z.string(),
   paths: z.array(z.string()).optional(),
   allowEmpty: z.boolean().optional(),
+  stagedOnly: z.boolean().optional(),
 });
 
 export type CommitInput = z.infer<typeof commitInput>;
@@ -241,6 +249,7 @@ export const createPrInput = z.object({
   prTitle: z.string().optional(),
   prBody: z.string().optional(),
   draft: z.boolean().optional(),
+  stagedOnly: z.boolean().optional(),
 });
 
 export type CreatePrInput = z.infer<typeof createPrInput>;

apps/code/src/main/services/git/service.ts

@@ -19,6 +19,8 @@ import {
   getUnstagedDiff,
   fetch as gitFetch,
   isGitRepository,
+  stageFiles,
+  unstageFiles,
 } from "@posthog/git/queries";
 import { CreateBranchSaga, SwitchBranchSaga } from "@posthog/git/sagas/branch";
 import { CloneSaga } from "@posthog/git/sagas/clone";
@@ -266,6 +268,7 @@ export class GitService extends TypedEventEmitter<GitServiceEvents> {
       originalPath: f.originalPath,
       linesAdded: f.linesAdded,
       linesRemoved: f.linesRemoved,
+      staged: f.staged,
     }));
   }
 
@@ -283,6 +286,36 @@ export class GitService extends TypedEventEmitter<GitServiceEvents> {
     return getDiffHead(directoryPath, { ignoreWhitespace });
   }
 
+  public async getDiffCached(
+    directoryPath: string,
+    ignoreWhitespace?: boolean,
+  ): Promise<string> {
+    return getStagedDiff(directoryPath, { ignoreWhitespace });
+  }
+
+  public async getDiffUnstaged(
+    directoryPath: string,
+    ignoreWhitespace?: boolean,
+  ): Promise<string> {
+    return getUnstagedDiff(directoryPath, { ignoreWhitespace });
+  }
+
+  public async stageFiles(
+    directoryPath: string,
+    paths: string[],
+  ): Promise<GitStateSnapshot> {
+    await stageFiles(directoryPath, paths);
+    return this.getStateSnapshot(directoryPath);
+  }
+
+  public async unstageFiles(
+    directoryPath: string,
+    paths: string[],
+  ): Promise<GitStateSnapshot> {
+    await unstageFiles(directoryPath, paths);
+    return this.getStateSnapshot(directoryPath);
+  }
+
   public async getDiffStats(directoryPath: string): Promise<DiffStats> {
     const stats = await getDiffStats(directoryPath, {
       excludePatterns: [".claude", "CLAUDE.local.md"],
@@ -479,6 +512,7 @@ export class GitService extends TypedEventEmitter<GitServiceEvents> {
     prTitle?: string;
     prBody?: string;
     draft?: boolean;
+    stagedOnly?: boolean;
   }): Promise<CreatePrOutput> {
     const { directoryPath, flowId } = input;
 
@@ -502,7 +536,7 @@ export class GitService extends TypedEventEmitter<GitServiceEvents> {
         checkoutBranch: (dir, name) => this.checkoutBranch(dir, name),
         getChangedFilesHead: (dir) => this.getChangedFilesHead(dir),
         generateCommitMessage: (dir) => this.generateCommitMessage(dir),
-        commit: (dir, msg) => this.commit(dir, msg),
+        commit: (dir, msg, stagedOnly) => this.commit(dir, msg, { stagedOnly }),
         getSyncStatus: (dir) => this.getGitSyncStatus(dir),
         push: (dir) => this.push(dir),
         publish: (dir) => this.publish(dir),
@@ -521,6 +555,7 @@ export class GitService extends TypedEventEmitter<GitServiceEvents> {
       prTitle: input.prTitle,
       prBody: input.prBody,
       draft: input.draft,
+      stagedOnly: input.stagedOnly,
     });
 
     if (!result.success) {
@@ -584,8 +619,7 @@ export class GitService extends TypedEventEmitter<GitServiceEvents> {
   public async commit(
     directoryPath: string,
     message: string,
-    paths?: string[],
-    allowEmpty?: boolean,
+    options?: { paths?: string[]; allowEmpty?: boolean; stagedOnly?: boolean },
   ): Promise<CommitOutput> {
     const fail = (msg: string): CommitOutput => ({
       success: false,
@@ -600,8 +634,7 @@ export class GitService extends TypedEventEmitter<GitServiceEvents> {
     const result = await saga.run({
       baseDir: directoryPath,
       message: message.trim(),
-      paths,
-      allowEmpty,
+      ...options,
     });
 
     if (!result.success) return fail(result.error);

apps/code/src/main/trpc/routers/git.ts

@@ -13,6 +13,8 @@ import {
   createPrOutput,
   detectRepoInput,
   detectRepoOutput,
+  diffInput,
+  diffOutput,
   discardFileChangesInput,
   discardFileChangesOutput,
   generateCommitMessageInput,
@@ -29,8 +31,6 @@ import {
   getCommitConventionsOutput,
   getCurrentBranchInput,
   getCurrentBranchOutput,
-  getDiffHeadInput,
-  getDiffHeadOutput,
   getDiffStatsInput,
   getDiffStatsOutput,
   getFileAtHeadInput,
@@ -45,6 +45,7 @@ import {
   getPrTemplateInput,
   getPrTemplateOutput,
   ghStatusOutput,
+  gitStateSnapshotSchema,
   openPrInput,
   openPrOutput,
   prStatusInput,
@@ -57,6 +58,7 @@ import {
   pushOutput,
   searchGithubIssuesInput,
   searchGithubIssuesOutput,
+  stageFilesInput,
   syncInput,
   syncOutput,
   validateRepoInput,
@@ -139,17 +141,45 @@ export const gitRouter = router({
     ),
 
   getDiffHead: publicProcedure
-    .input(getDiffHeadInput)
-    .output(getDiffHeadOutput)
+    .input(diffInput)
+    .output(diffOutput)
     .query(({ input }) =>
       getService().getDiffHead(input.directoryPath, input.ignoreWhitespace),
     ),
 
+  getDiffCached: publicProcedure
+    .input(diffInput)
+    .output(diffOutput)
+    .query(({ input }) =>
+      getService().getDiffCached(input.directoryPath, input.ignoreWhitespace),
+    ),
+
+  getDiffUnstaged: publicProcedure
+    .input(diffInput)
+    .output(diffOutput)
+    .query(({ input }) =>
+      getService().getDiffUnstaged(input.directoryPath, input.ignoreWhitespace),
+    ),
+
   getDiffStats: publicProcedure
     .input(getDiffStatsInput)
     .output(getDiffStatsOutput)
     .query(({ input }) => getService().getDiffStats(input.directoryPath)),
 
+  stageFiles: publicProcedure
+    .input(stageFilesInput)
+    .output(gitStateSnapshotSchema)
+    .mutation(({ input }) =>
+      getService().stageFiles(input.directoryPath, input.paths),
+    ),
+
+  unstageFiles: publicProcedure
+    .input(stageFilesInput)
+    .output(gitStateSnapshotSchema)
+    .mutation(({ input }) =>
+      getService().unstageFiles(input.directoryPath, input.paths),
+    ),
+
   discardFileChanges: publicProcedure
     .input(discardFileChangesInput)
     .output(discardFileChangesOutput)
@@ -189,12 +219,11 @@ export const gitRouter = router({
     .input(commitInput)
     .output(commitOutput)
     .mutation(({ input }) =>
-      getService().commit(
-        input.directoryPath,
-        input.message,
-        input.paths,
-        input.allowEmpty,
-      ),
+      getService().commit(input.directoryPath, input.message, {
+        paths: input.paths,
+        allowEmpty: input.allowEmpty,
+        stagedOnly: input.stagedOnly,
+      }),
     ),
 
   push: publicProcedure