refactor: Optional development environment separate from production database for testing purposes

CONTRIBUTING.md

@@ -37,6 +37,48 @@ go build -o tmpo .
 ./tmpo --help
 ```
 
+### Development Mode
+
+To prevent corrupting your real tmpo data during development, use the `TMPO_DEV` environment variable:
+
+```bash
+# Enable development mode (uses ~/.tmpo-dev/ instead of ~/.tmpo/)
+export TMPO_DEV=1
+
+# Now all commands use the development database
+./tmpo start "Testing new feature"
+./tmpo status
+./tmpo stop
+```
+
+**Database Locations:**
+
+- **Production mode** (default): `~/.tmpo/tmpo.db`
+- **Development mode** (`TMPO_DEV=1`): `~/.tmpo-dev/tmpo.db`
+
+> [!NOTE]
+> The `export TMPO_DEV=1` command only applies to your **current terminal session**. When you close the terminal, it resets to production mode. This is intentional for safety - you must explicitly enable dev mode each time.
+
+**Making it persistent (optional):**
+
+If you prefer to always use dev mode, add it to your shell profile:
+
+```bash
+# For zsh (macOS default)
+echo 'export TMPO_DEV=1' >> ~/.zshrc
+
+# For bash
+echo 'export TMPO_DEV=1' >> ~/.bashrc
+```
+
+Then restart your terminal or run `source ~/.zshrc` (or `source ~/.bashrc`).
+
+**Benefits of development mode:**
+
+- Your real time tracking data stays safe
+- You can test database changes without risk
+- You can easily clean up test data (`rm -rf ~/.tmpo-dev/`)
+
 ### Building with Version Information
 
 To build with version information injected (useful for testing version display):
@@ -120,16 +162,22 @@ tmpo/
 All user data is stored locally in:
 
 ```
-~/.tmpo/
-  └── tmpo.db          # SQLite database
+~/.tmpo/              # Production (default)
+  └── tmpo.db
+
+~/.tmpo-dev/          # Development (when TMPO_DEV=1)
+  └── tmpo.db
 ```
 
 The database schema includes:
 
-- Time entries (start/end times, project, description)
+- Time entries (start/end times, project, description, hourly rate)
 - Project metadata (derived from entries)
 - Automatic indexing for fast queries
 
+> [!NOTE]
+> See [Development Mode](#development-mode) for information on using the development database during local development.
+
 ### How Project Detection Works
 
 When a user runs `tmpo start`, the project name is detected in this priority order:

internal/storage/db.go

@@ -24,11 +24,14 @@ type Database struct {
 
 // Initialize ensures the on-disk storage for the application exists, opens the
 // SQLite database, and returns a Database wrapper.
-// 
+//
 // Specifically, Initialize:
 //   - determines the current user's home directory,
-//   - creates the directory "$HOME/.tmpo" if it does not already exist,
-//   - opens (or creates) the SQLite database file "$HOME/.tmpo/tmpo.db",
+//   - checks the TMPO_DEV environment variable:
+//     - if TMPO_DEV is "1" or "true", uses "$HOME/.tmpo-dev" (development mode),
+//     - otherwise uses "$HOME/.tmpo" (production mode, the default),
+//   - creates the appropriate directory if it does not already exist,
+//   - opens (or creates) the SQLite database file "tmpo.db" in that directory,
 //   - ensures the time_entries table exists with the schema:
 //       id INTEGER PRIMARY KEY AUTOINCREMENT,
 //       project_name TEXT NOT NULL,
@@ -42,12 +45,17 @@ type Database struct {
 // responsible for closing the database when finished.
 func Initialize() (*Database, error) {
 	homeDir, err := os.UserHomeDir()
-	
+
 	if err != nil {
 		return nil, fmt.Errorf("failed to get home directory: %w", err)
 	}
 
+	// Switch out directory depending on build environment
 	tmpoDir := filepath.Join(homeDir, ".tmpo")
+	if devMode := os.Getenv("TMPO_DEV"); devMode == "1" || devMode == "true" {
+		tmpoDir = filepath.Join(homeDir, ".tmpo-dev")
+	}
+
 	if err := os.MkdirAll(tmpoDir, 0755); err != nil {
 		return nil, fmt.Errorf("failed to create .tmpo directory: %w", err)
 	}