revset: add hint to innermost error

This seems more useful if aliases are nested. The innermost error usually
contains the problem, and the outer errors are contexts where aliases are
expanded.

cli/src/cli_util.rs

@@ -405,9 +405,10 @@ impl From<RevsetEvaluationError> for CommandError {
 
 impl From<RevsetParseError> for CommandError {
     fn from(err: RevsetParseError) -> Self {
-        let message = iter::successors(Some(&err), |e| e.origin()).join("\n");
-        // Only for the top-level error as we can't attach hint to inner errors
-        let hint = match err.kind() {
+        let err_chain = iter::successors(Some(&err), |e| e.origin());
+        let message = err_chain.clone().join("\n");
+        // Only for the bottom error, which is usually the root cause
+        let hint = match err_chain.last().unwrap().kind() {
             RevsetParseErrorKind::NotPrefixOperator {
                 op: _,
                 similar_op,

cli/tests/test_revset_output.rs

@@ -228,6 +228,7 @@ fn test_function_name_hint() {
     'branches(x)' = 'x' # override builtin function
     'my_author(x)' = 'author(x)' # similar name to builtin function
     'author_sym' = 'x' # not a function alias
+    'my_branches' = 'branch()' # typo in alias
     "###,
     );
 
@@ -252,6 +253,22 @@ fn test_function_name_hint() {
       = Revset function "author_" doesn't exist
     Hint: Did you mean "author", "my_author"?
     "###);
+
+    insta::assert_snapshot!(evaluate_err("my_branches"), @r###"
+    Error: Failed to parse revset:  --> 1:1
+      |
+    1 | my_branches
+      | ^---------^
+      |
+      = Alias "my_branches" cannot be expanded
+     --> 1:1
+      |
+    1 | branch()
+      | ^----^
+      |
+      = Revset function "branch" doesn't exist
+    Hint: Did you mean "branches"?
+    "###);
 }
 
 #[test]