feat(meta): add about meta-command

grammar.ebnf

@@ -9,6 +9,7 @@ insert       ::= "insert"
 select       ::= "select"
 
 meta-command ::= "." "exit"
+                   | "about"
 
 int          ::= sign? digit+
 sign         ::= "+"

notes.org

@@ -229,6 +229,7 @@ i will use rustyline, since it seems like the most feature-complete
 * TODO .about meta-command
 * TODO .version meta-command
 * TODO .license meta-command
+* TODO .help meta-command
 
 * TODO parse insert statements in the form
 insert <id:int> <username:string> <email:string>

src/branding.rs

@@ -2,13 +2,31 @@
 use insta::assert_snapshot;
 
 pub fn startup_msg() -> String {
-    let name = env!("CARGO_PKG_NAME");
-    let version = env!("CARGO_PKG_VERSION");
     let authors = env!("CARGO_PKG_AUTHORS");
+    let about = about_msg();
+    let shorthelp = shorthelp_msg();
 
     format!(
-        "{name} v{version} started.\n\
-        Copyright 2025 {authors}. All rights reserved."
+        "{about}\n\n\
+        Copyright 2025 {authors}. All rights reserved.\n\n\
+        {shorthelp}"
+    )
+}
+
+pub fn about_msg() -> String {
+    let name = env!("CARGO_PKG_NAME");
+    let version = env!("CARGO_PKG_VERSION");
+
+    format!(
+        "{name} v{version} -- A database engine\n\
+        Note: This is experimental software. No maintenance is intendend."
+    )
+}
+
+pub fn shorthelp_msg() -> String {
+    String::from(
+        "Type .license for licensing information\n\
+        Type .help for usage information",
     )
 }
 

src/meta_commands.rs

@@ -1,12 +1,16 @@
+use crate::branding;
+
 #[derive(Debug, Eq, PartialEq)]
 pub enum MetaCommand {
     Exit,
+    About,
 }
 
 impl std::fmt::Display for MetaCommand {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         match self {
             MetaCommand::Exit => write!(f, "exit"),
+            MetaCommand::About => write!(f, "about"),
         }
     }
 }
@@ -19,6 +23,10 @@ impl MetaCommand {
     pub fn execute(&self) -> MetaCommandExecuteResult {
         match self {
             MetaCommand::Exit => MetaCommandExecuteResult { should_exit: true },
+            MetaCommand::About => {
+                print!("{}", branding::about_msg());
+                MetaCommandExecuteResult { should_exit: false }
+            }
         }
     }
 }

src/snapshots/osdb__branding__startup_msg.snap

@@ -2,5 +2,10 @@
 source: src/branding.rs
 expression: startup_msg()
 ---
-osdb v0.1.0 started.
+osdb v0.1.0 -- A database engine
+Note: This is experimental software. No maintenance is intendend.
+
 Copyright 2025 Khaïs COLIN. All rights reserved.
+
+Type .license for licensing information
+Type .help for usage information

src/tokens.rs

@@ -160,6 +160,7 @@ impl Tokenizer {
     fn recognize_metacommand(word: &str) -> Option<TokenData> {
         match word.to_lowercase().as_str() {
             ".exit" => Some(TokenData::MetaCommand(MetaCommand::Exit)),
+            ".about" => Some(TokenData::MetaCommand(MetaCommand::About)),
             _ => None,
         }
     }