From 99c42c5a8f2cd4d302a2728c11ca72d067e6058e Mon Sep 17 00:00:00 2001
From: Noah Mayr <dev@noahmayr.com>
Date: Mon, 1 Apr 2024 18:01:12 +0200
Subject: [PATCH] cli: add better error message when immutable_heads() cannot
 be resolved

---
 cli/src/cli_util.rs  | 24 +++++++++++++++++++++---
 docs/contributing.md |  2 +-
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/cli/src/cli_util.rs b/cli/src/cli_util.rs
index 71af456307e..0095c7ee5ad 100644
--- a/cli/src/cli_util.rs
+++ b/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 +1012,25 @@ 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(format!(
+                    "The expression '{}' of immutable_heads() could not be resolved, if you \
+                     configured specific branch names consider wrapping them with 'present()' or \
+                     using the functions 'branches()' / 'remote_branches()'.",
+                    name
+                ))
+            })?
+            .next()
+        {
             let error = if &commit_id == self.repo().store().root_commit_id() {
                 user_error(format!(
                     "The root commit {} is immutable",
diff --git a/docs/contributing.md b/docs/contributing.md
index c4c75c64480..d1df5da243c 100644
--- a/docs/contributing.md
+++ b/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