Add commitAll and rollbackAll in sessions and recommend rollbackAll in defer in docs.

docs/docs/database.md

@@ -51,7 +51,19 @@ defer session.deinit();
 
 Using sessions, you can start transactions and use savepoints.
 
+::: warning
+You probably want to rollback all active transactions in `defer`, so that none remain active after leaving the active branch.
+:::
+
 ```zig
+// Start a new session.
+var session = try zrm.Session.init(database);
+defer {
+	// Rollback all active transactions that remain active.
+	session.rollbackAll();
+	session.deinit();
+};
+
 try session.beginTransaction();
 
 // Do something.

src/session.zig

@@ -12,6 +12,9 @@ pub const Session = struct {
 	/// The active connection for the session.
 	connection: *pg.Conn,
 
+	/// The count of active transactions for the session.
+	activeTransactions: usize = 0,
+
 	/// Execute a comptime-known SQL command for the current session.
 	fn exec(self: Self, comptime sql: []const u8) !void {
 		_ = self.connection.exec(sql, .{}) catch |err| {
@@ -29,11 +32,25 @@ pub const Session = struct {
 		try self.exec("ROLLBACK;");
 	}
 
+	/// Rollback all active transactions.
+	pub fn rollbackAll(self: Self) !void {
+		for (0..self.activeTransactions) |_| {
+			self.rollbackTransaction();
+		}
+	}
+
 	/// Commit the current transaction.
 	pub fn commitTransaction(self: Self) !void {
 		try self.exec("COMMIT;");
 	}
 
+	/// Commit all active transactions.
+	pub fn commitAll(self: Self) !void {
+		for (0..self.activeTransactions) |_| {
+			self.commitTransaction();
+		}
+	}
+
 	/// Create a new savepoint with the given name.
 	pub fn savepoint(self: Self, comptime _savepoint: []const u8) !void {
 		try self.exec("SAVEPOINT " ++ _savepoint ++ ";");