bump max layer default

and save one layer for remaining content

src/image_layerer/mod.rs

@@ -51,7 +51,7 @@ pub struct ImageLayerer {
     #[builder(setter(custom))]
     oci_dir: OciDir,
     /// The maximum number of layers to create.
-    /// The default is 100.
+    /// The default is 125.
     #[builder(default = "default_max_layers()")]
     max_layers: usize,
     /// The time the image was created.
@@ -91,7 +91,7 @@ impl ImageLayererBuilder {
 }
 
 fn default_max_layers() -> usize {
-    100
+    125
 }
 
 fn default_creation_time() -> DateTime<chrono::Utc> {
@@ -142,7 +142,7 @@ impl ImageLayerer {
     /// Returns the descriptor for the image manifest.
     pub fn create_image(self) -> Result<Descriptor> {
         // Determine most popular packages
-        let popular_packages = most_popular_packages(&self.filesystem_root, self.max_layers)?;
+        let popular_packages = most_popular_packages(&self.filesystem_root, self.max_layers - 1)?;
         // Create a a layer for each package
         let mut package_layers = self.package_layers(&popular_packages)?;
         let path_to_layer_map = path_to_layer_map(popular_packages);