feat: add @automaker/git-utils package

ELIMINATES routes/common.ts: Extract all git operations (382 lines) into dedicated package.

- Extract git status parsing (parseGitStatus, isGitRepo)
- Extract diff generation (generateSyntheticDiffForNewFile, etc.)
- Extract repository analysis (getGitRepositoryDiffs)
- Handle both git repos and non-git directories
- Support binary file detection
- Generate synthetic diffs for untracked files

Split into logical modules:
- types.ts: Constants and interfaces
- status.ts: Git status operations
- diff.ts: Diff generation utilities

This package will replace:
- apps/server/src/routes/common.ts (to be deleted)

Dependencies: @automaker/types, @automaker/utils

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

libs/git-utils/src/status.ts

@@ -0,0 +1,99 @@
+/**
+ * Git status parsing utilities
+ */
+
+import { exec } from "child_process";
+import { promisify } from "util";
+import { GIT_STATUS_MAP, type FileStatus } from './types';
+
+const execAsync = promisify(exec);
+
+/**
+ * Get a readable status text from git status codes
+ * Handles both single character and XY format status codes
+ */
+function getStatusText(indexStatus: string, workTreeStatus: string): string {
+  // Untracked files
+  if (indexStatus === "?" && workTreeStatus === "?") {
+    return "Untracked";
+  }
+
+  // Ignored files
+  if (indexStatus === "!" && workTreeStatus === "!") {
+    return "Ignored";
+  }
+
+  // Prioritize staging area status, then working tree
+  const primaryStatus = indexStatus !== " " && indexStatus !== "?" ? indexStatus : workTreeStatus;
+
+  // Handle combined statuses
+  if (indexStatus !== " " && indexStatus !== "?" && workTreeStatus !== " " && workTreeStatus !== "?") {
+    // Both staging and working tree have changes
+    const indexText = GIT_STATUS_MAP[indexStatus] || "Changed";
+    const workText = GIT_STATUS_MAP[workTreeStatus] || "Changed";
+    if (indexText === workText) {
+      return indexText;
+    }
+    return `${indexText} (staged), ${workText} (unstaged)`;
+  }
+
+  return GIT_STATUS_MAP[primaryStatus] || "Changed";
+}
+
+/**
+ * Check if a path is a git repository
+ */
+export async function isGitRepo(repoPath: string): Promise<boolean> {
+  try {
+    await execAsync("git rev-parse --is-inside-work-tree", { cwd: repoPath });
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+/**
+ * Parse the output of `git status --porcelain` into FileStatus array
+ * Git porcelain format: XY PATH where X=staging area status, Y=working tree status
+ * For renamed files: XY ORIG_PATH -> NEW_PATH
+ */
+export function parseGitStatus(statusOutput: string): FileStatus[] {
+  return statusOutput
+    .split("\n")
+    .filter(Boolean)
+    .map((line) => {
+      // Git porcelain format uses two status characters: XY
+      // X = status in staging area (index)
+      // Y = status in working tree
+      const indexStatus = line[0] || " ";
+      const workTreeStatus = line[1] || " ";
+
+      // File path starts at position 3 (after "XY ")
+      let filePath = line.slice(3);
+
+      // Handle renamed files (format: "R  old_path -> new_path")
+      if (indexStatus === "R" || workTreeStatus === "R") {
+        const arrowIndex = filePath.indexOf(" -> ");
+        if (arrowIndex !== -1) {
+          filePath = filePath.slice(arrowIndex + 4); // Use new path
+        }
+      }
+
+      // Determine the primary status character for backwards compatibility
+      // Prioritize staging area status, then working tree
+      let primaryStatus: string;
+      if (indexStatus === "?" && workTreeStatus === "?") {
+        primaryStatus = "?"; // Untracked
+      } else if (indexStatus !== " " && indexStatus !== "?") {
+        primaryStatus = indexStatus; // Staged change
+      } else {
+        primaryStatus = workTreeStatus; // Working tree change
+      }
+
+      return {
+        status: primaryStatus,
+        path: filePath,
+        statusText: getStatusText(indexStatus, workTreeStatus),
+      };
+    });
+}