feat: auto-detect git worktree context from git commands

When HAPI_WORKTREE_* environment variables are not set, fall back to
probing git to detect if running inside a worktree. This enables
worktree features to work automatically without explicit env vars.

cli/src/utils/worktreeEnv.ts

@@ -1,26 +1,120 @@
+import { execFileSync } from 'node:child_process';
+import { realpathSync, statSync } from 'node:fs';
+import { basename, dirname, isAbsolute, resolve } from 'node:path';
+
 import type { WorktreeInfo } from '@/daemon/worktree';
+import { logger } from '@/ui/logger';
 
 export function readWorktreeEnv(): WorktreeInfo | null {
-  const basePath = process.env.HAPI_WORKTREE_BASE_PATH?.trim();
-  const branch = process.env.HAPI_WORKTREE_BRANCH?.trim();
-  const name = process.env.HAPI_WORKTREE_NAME?.trim();
-  const worktreePath = process.env.HAPI_WORKTREE_PATH?.trim();
-  const createdAtRaw = process.env.HAPI_WORKTREE_CREATED_AT?.trim();
-
-  if (!basePath || !branch || !name || !worktreePath || !createdAtRaw) {
-    return null;
-  }
-
-  const createdAt = Number(createdAtRaw);
-  if (!Number.isFinite(createdAt)) {
-    return null;
-  }
-
-  return {
-    basePath,
-    branch,
-    name,
-    worktreePath,
-    createdAt
-  };
+    return readWorktreeFromEnv() ?? readWorktreeFromGit();
+}
+
+function readWorktreeFromEnv(): WorktreeInfo | null {
+    const basePath = process.env.HAPI_WORKTREE_BASE_PATH?.trim();
+    const branch = process.env.HAPI_WORKTREE_BRANCH?.trim();
+    const name = process.env.HAPI_WORKTREE_NAME?.trim();
+    const worktreePath = process.env.HAPI_WORKTREE_PATH?.trim();
+    const createdAtRaw = process.env.HAPI_WORKTREE_CREATED_AT?.trim();
+
+    if (!basePath || !branch || !name || !worktreePath || !createdAtRaw) {
+        return null;
+    }
+
+    const createdAt = Number(createdAtRaw);
+    if (!Number.isFinite(createdAt)) {
+        return null;
+    }
+
+    return {
+        basePath,
+        branch,
+        name,
+        worktreePath,
+        createdAt
+    };
+}
+
+function readWorktreeFromGit(): WorktreeInfo | null {
+    const start = Date.now();
+    let result: WorktreeInfo | null = null;
+
+    try {
+        const cwd = process.cwd();
+        const isInside = runGit(['rev-parse', '--is-inside-work-tree'], cwd);
+        if (isInside !== 'true') {
+            return null;
+        }
+
+        const gitDir = runGit(['rev-parse', '--git-dir'], cwd);
+        const gitCommonDir = runGit(['rev-parse', '--git-common-dir'], cwd);
+        if (!gitDir || !gitCommonDir) {
+            return null;
+        }
+
+        const resolvedGitDir = normalizePath(gitDir, cwd);
+        const resolvedGitCommonDir = normalizePath(gitCommonDir, cwd);
+        if (resolvedGitDir === resolvedGitCommonDir) {
+            return null;
+        }
+
+        const worktreeRoot = runGit(['rev-parse', '--show-toplevel'], cwd);
+        if (!worktreeRoot) {
+            return null;
+        }
+        const worktreePath = normalizePath(worktreeRoot, cwd);
+        const basePath = dirname(resolvedGitCommonDir);
+
+        const branch = runGit(['symbolic-ref', '--short', 'HEAD'], cwd)
+            ?? runGit(['rev-parse', '--short', 'HEAD'], cwd);
+        if (!branch) {
+            return null;
+        }
+
+        result = {
+            basePath,
+            branch,
+            name: basename(worktreePath),
+            worktreePath,
+            createdAt: readCreatedAt(worktreePath)
+        };
+        return result;
+    } finally {
+        const elapsedMs = Date.now() - start;
+        logger.debug(`[WORKTREE] Git probe ${result ? 'hit' : 'miss'} in ${elapsedMs}ms`);
+    }
+}
+
+function runGit(args: string[], cwd: string): string | null {
+    try {
+        const output = execFileSync('git', args, { cwd, encoding: 'utf8' }).trim();
+        return output.length > 0 ? output : null;
+    } catch {
+        return null;
+    }
+}
+
+function normalizePath(rawPath: string, cwd: string): string {
+    const resolved = isAbsolute(rawPath) ? rawPath : resolve(cwd, rawPath);
+    try {
+        return realpathSync(resolved);
+    } catch {
+        return resolved;
+    }
+}
+
+function readCreatedAt(worktreePath: string): number {
+    try {
+        const stat = statSync(worktreePath);
+        const birthtimeMs = Math.round(stat.birthtimeMs);
+        if (Number.isFinite(birthtimeMs) && birthtimeMs > 0) {
+            return birthtimeMs;
+        }
+        const ctimeMs = Math.round(stat.ctimeMs);
+        if (Number.isFinite(ctimeMs) && ctimeMs > 0) {
+            return ctimeMs;
+        }
+    } catch {
+        return Date.now();
+    }
+    return Date.now();
 }