cli: make "debug revset" print expression for each stage

It helps while debugging tree substitution.

src/cli_util.rs

@@ -881,7 +881,11 @@ impl WorkspaceCommandHelper {
         Ok(revset_expression.evaluate(self.repo.as_ref())?)
     }
 
-    fn revset_context(&self) -> RevsetWorkspaceContext {
+    pub(crate) fn revset_aliases_map(&self) -> &RevsetAliasesMap {
+        &self.revset_aliases_map
+    }
+
+    pub(crate) fn revset_context(&self) -> RevsetWorkspaceContext {
         RevsetWorkspaceContext {
             cwd: &self.cwd,
             workspace_id: self.workspace_id(),

src/commands/mod.rs

@@ -3181,14 +3181,33 @@ fn cmd_debug_revset(
     args: &DebugRevsetArgs,
 ) -> Result<(), CommandError> {
     let workspace_command = command.workspace_helper(ui)?;
-    let expression = workspace_command.parse_revset(&args.revision)?;
+    let workspace_ctx = workspace_command.revset_context();
-    writeln!(ui, "-- Expression:")?;
+    let repo = workspace_command.repo().as_ref();
+
+    let expression = revset::parse(
+        &args.revision,
+        workspace_command.revset_aliases_map(),
+        Some(&workspace_ctx),
+    )?;
+    writeln!(ui, "-- Parsed:")?;
     writeln!(ui, "{expression:#?}")?;
     writeln!(ui)?;
-    let revset = workspace_command.evaluate_revset(expression)?;
+
+    let expression = revset::optimize(expression);
+    writeln!(ui, "-- Optimized:")?;
+    writeln!(ui, "{expression:#?}")?;
+    writeln!(ui)?;
+
+    let expression = revset::resolve_symbols(repo, expression, Some(&workspace_ctx))?;
+    writeln!(ui, "-- Resolved:")?;
+    writeln!(ui, "{expression:#?}")?;
+    writeln!(ui)?;
+
+    let revset = expression.evaluate(repo)?;
     writeln!(ui, "-- Evaluated:")?;
     writeln!(ui, "{revset:#?}")?;
     writeln!(ui)?;
+
     writeln!(ui, "-- Commit IDs:")?;
     for commit_id in revset.iter() {
         writeln!(ui, "{}", commit_id.hex())?;

tests/test_debug_command.rs

@@ -30,11 +30,21 @@ fn test_debug_revset() {
         (r"(?m)(^    .*\n)+", "    ..\n"),
     ]}, {
         assert_snapshot!(stdout, @r###"
-        -- Expression:
+        -- Parsed:
         Symbol(
             ..
         )
 
+        -- Optimized:
+        Symbol(
+            ..
+        )
+
+        -- Resolved:
+        Commits(
+            ..
+        )
+
         -- Evaluated:
         RevsetImpl {
             ..