Clarify directionality of layer stacks

Signed-off-by: Ryan Bottriell <rbottriell@ilm.com>

crates/spfs-cli/main/src/cmd_info.rs

@@ -109,9 +109,9 @@ impl CmdInfo {
                     "refs:".bright_blue(),
                     self.format_digest(obj.digest()?, repo).await?
                 );
-                println!("{}", "stack:".bright_blue());
-                for reference in obj.stack {
-                    println!("  - {}", self.format_digest(reference, repo).await?);
+                println!("{}", "stack (top-down):".bright_blue());
+                for reference in obj.stack.iter().rev() {
+                    println!("  - {}", self.format_digest(*reference, repo).await?);
                 }
             }
 
@@ -187,15 +187,11 @@ impl CmdInfo {
     async fn print_global_info(&self, repo: &spfs::storage::RepositoryHandle) -> Result<()> {
         let runtime = spfs::active_runtime().await?;
 
-        println!("{}", "Active Runtime:".green());
-        println!(" {}: {}", "id:".bright_blue(), runtime.name());
-        println!(
-            " {}: {}",
-            "editable:".bright_blue(),
-            runtime.status.editable
-        );
-        println!("{}", "stack".bright_blue());
-        for digest in runtime.status.stack.iter() {
+        println!("{}:", "Active Runtime".green());
+        println!(" {}: {}", "id".bright_blue(), runtime.name());
+        println!(" {}: {}", "editable".bright_blue(), runtime.status.editable);
+        println!("{}:", "stack (top-down)".bright_blue());
+        for digest in runtime.status.stack.iter().rev() {
             print!("  - {}, ", self.format_digest(*digest, repo).await?);
             let object = repo.read_ref(digest.to_string().as_str()).await?;
             println!(

crates/spfs/src/graph/platform.rs

@@ -16,6 +16,7 @@ mod platform_test;
 /// future runtimes.
 #[derive(Debug, Eq, PartialEq, Default, Clone)]
 pub struct Platform {
+    /// Items in the platform, with the top-most/override entry being last
     pub stack: Vec<encoding::Digest>,
 }
 

crates/spfs/src/runtime/storage.rs

@@ -74,6 +74,7 @@ impl Default for Author {
 #[derive(Serialize, Deserialize, Debug, Clone, Default, PartialEq, Eq)]
 pub struct Status {
     /// The set of layers that are being used in this runtime
+    /// with the top-most/override layer being last
     pub stack: Vec<encoding::Digest>,
     /// Additional layers that were created automatically due to the stack
     /// being too large.
@@ -874,7 +875,6 @@ impl Runtime {
     /// update any currently running environment.
     pub fn push_digest(&mut self, digest: encoding::Digest) {
         let mut new_stack = Vec::with_capacity(self.status.stack.len() + 1);
-        new_stack.push(digest);
         for existing in self.status.stack.drain(..) {
             // we do not want the same layer showing up twice, one for
             // efficiency and two it causes errors in overlayfs so promote
@@ -884,6 +884,7 @@ impl Runtime {
             }
             new_stack.push(existing);
         }
+        new_stack.push(digest);
         self.status.stack = new_stack;
     }