use canonical (unescapable) url format by default

README.md

@@ -53,7 +53,7 @@ snac2nex -s /path/to/snac/storage -t /path/to/nex -u user1 -u user2
           * escaped with `%%`
           * be careful when removing seconds, as it may cause overwrite collisions
 
-          [default: %H:%M:%S]
+          [default: %H-%M-%S]
 
       --format-updated <FORMAT_UPDATED>
           Post `{updated}` time format

src/config.rs

@@ -37,7 +37,7 @@ pub struct Config {
     ///
     /// * escaped with `%%`
     /// * be careful when removing seconds, as it may cause overwrite collisions
-    #[arg(long, default_value_t = String::from("%H:%M:%S"))]
+    #[arg(long, default_value_t = String::from("%H-%M-%S"))]
     pub format_filename: String,
 
     /// Post `{updated}` time format