adjust api, test commands with a greenmail instance

src/folder/arg/name.rs

@@ -1,11 +1,12 @@
 use clap::Parser;
 use email::account::config::DEFAULT_INBOX_FOLDER;
 
-/// The folder name argument parser.
+/// The optional folder name flag parser.
 #[derive(Debug, Parser)]
-pub struct FolderNameArg {
+pub struct FolderNameOptionalFlag {
     /// The name of the folder.
-    #[arg(name = "folder_name", value_name = "FOLDER")]
+    #[arg(long = "folder", short = 'f')]
+    #[arg(name = "folder_name", value_name = "NAME", default_value = DEFAULT_INBOX_FOLDER)]
     pub name: String,
 }
 
@@ -17,6 +18,14 @@ pub struct FolderNameOptionalArg {
     pub name: String,
 }
 
+/// The required folder name argument parser.
+#[derive(Debug, Parser)]
+pub struct FolderNameArg {
+    /// The name of the folder.
+    #[arg(name = "folder_name", value_name = "FOLDER")]
+    pub name: String,
+}
+
 /// The source folder name argument parser.
 #[derive(Debug, Parser)]
 pub struct SourceFolderNameArg {

src/folder/command/mod.rs

@@ -16,8 +16,8 @@ use self::{
 
 /// Manage folders.
 ///
-/// A folder (AKA mailbox, or directory) contains envelopes and
-/// messages. This subcommand allows you to manage them.
+/// A folder (as known as mailbox, or directory) contains one or more
+/// emails. This subcommand allows you to manage them.
 #[derive(Debug, Subcommand)]
 pub enum FolderSubcommand {
     #[command(alias = "add", alias = "new")]