cli: add better error message when immutable_heads() cannot be resolved

cli/src/cli_util.rs

@@ -53,7 +53,7 @@ use jj_lib::repo::{
 use jj_lib::repo_path::{FsPathParseError, RepoPath, RepoPathBuf};
 use jj_lib::revset::{
     RevsetAliasesMap, RevsetCommitRef, RevsetExpression, RevsetFilterPredicate, RevsetIteratorExt,
-    RevsetParseContext, RevsetWorkspaceContext,
+    RevsetParseContext, RevsetResolutionError, RevsetWorkspaceContext,
 };
 use jj_lib::rewrite::restore_tree;
 use jj_lib::settings::{ConfigResultExt as _, UserSettings};
@@ -88,7 +88,7 @@ use crate::git_util::{
 };
 use crate::merge_tools::{DiffEditor, MergeEditor, MergeToolConfigError};
 use crate::operation_templater::OperationTemplateLanguageExtension;
-use crate::revset_util::RevsetExpressionEvaluator;
+use crate::revset_util::{RevsetExpressionEvaluator, UserRevsetEvaluationError};
 use crate::template_builder::TemplateLanguage;
 use crate::template_parser::TemplateAliasesMap;
 use crate::templater::{PropertyPlaceholder, TemplateRenderer};
@@ -1012,7 +1012,22 @@ impl WorkspaceCommandHelper {
         let immutable = revset_util::parse_immutable_expression(&self.revset_parse_context())?;
         let mut expression = self.attach_revset_evaluator(immutable)?;
         expression.intersect_with(&to_rewrite_revset);
-        if let Some(commit_id) = expression.evaluate_to_commit_ids()?.next() {
+        if let Some(commit_id) = expression
+            .evaluate_to_commit_ids()
+            .map_err(|e| {
+                let UserRevsetEvaluationError::Resolution(RevsetResolutionError::NoSuchRevision {
+                    name,
+                    candidates: _,
+                }) = e
+                else {
+                    return e.into();
+                };
+                user_error_with_hint(format!(
+                    r#"The revision "{name}" used in immutable_heads() does not exist"#
+                ), r#"If you configured specific branch names consider wrapping them with "present()" or using the functions "branches()" / "remote_branches()"."#)
+            })?
+            .next()
+        {
             let error = if &commit_id == self.repo().store().root_commit_id() {
                 user_error(format!(
                     "The root commit {} is immutable",

docs/contributing.md

@@ -114,7 +114,7 @@ You will probably also want to make the `gh-pages` branch immutable (and thereby
 hidden from the default `jj log` output) by running the following in your repo:
 
 ```shell
-jj config set --repo "revset-aliases.immutable_heads()" "main@origin | gh-pages@origin"
+jj config set --repo "revset-aliases.immutable_heads()" 'remote_branches(exact:"main") | remote_branches(exact:"origin")'
 ```
 
 ### Summary