fix revision check logic

src/command/config.rs

@@ -72,6 +72,8 @@ fn current_revision() -> Result<Revision, RevisionCheckError> {
 
     let server_config_revision = toml::from_str::<Config>(&buffer)?.config_revision;
 
+    buffer.clear();
+
     let mut client_toml = fs::File::open(CLIENT_CONFIG_PATH)?;
     client_toml.read_to_string(&mut buffer)?;
 
@@ -83,7 +85,12 @@ fn current_revision() -> Result<Revision, RevisionCheckError> {
         ));
     }
 
-    Ok(server_config_revision)
+    match server_config_revision {
+        Revision::V0 => Err(RevisionCheckError::UnknownRevision(
+            "revision 0 does not exist",
+        )),
+        _ => Ok(server_config_revision),
+    }
 }
 
 pub(crate) async fn run(command: Commands) -> Result<(), ConfigError> {