cli: warn when invalid fileset expressions look like file paths

CHANGELOG.md

@@ -97,6 +97,9 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 * Color author and committer names yellow
 
+* Commands accepting filesets suggest to use escaping if invalid fileset expressions
+  look like file paths.
+
 ### Fixed bugs
 
 * Update working copy before reporting changes. This prevents errors during reporting

cli/src/cli_util.rs

@@ -1093,17 +1093,34 @@ impl WorkspaceCommandHelper {
         if values.is_empty() {
             Ok(FilesetExpression::all())
         } else if self.settings().config().get_bool("ui.allow-filesets")? {
-            self.parse_union_filesets(ui, values)
+            self.parse_union_filesets(ui, values).map_err(|mut e| {
+                if self.parse_file_path_expressions(values).is_ok() {
+                    e.add_hint(
+                        "Filesets are enabled by default. If you want to match file paths \
+                         containing characters used in fileset expressions (':', or '~'), escape \
+                         them, or prefix them with \"glob:\".",
+                    );
+                }
+                e
+            })
         } else {
-            let expressions = values
-                .iter()
-                .map(|v| self.parse_file_path(v))
-                .map_ok(FilesetExpression::prefix_path)
-                .try_collect()?;
-            Ok(FilesetExpression::union_all(expressions))
+            self.parse_file_path_expressions(values)
+                .map(FilesetExpression::union_all)
         }
     }
 
+    fn parse_file_path_expressions(
+        &self,
+        values: &[String],
+    ) -> Result<Vec<FilesetExpression>, CommandError> {
+        let expressions = values
+            .iter()
+            .map(|v| self.parse_file_path(v))
+            .map_ok(FilesetExpression::prefix_path)
+            .try_collect()?;
+        Ok(expressions)
+    }
+
     /// Parses the given fileset expressions and concatenates them all.
     pub fn parse_union_filesets(
         &self,

cli/tests/test_global_opts.rs

@@ -291,6 +291,31 @@ fn test_bad_path() {
     "###);
 }
 
+#[test]
+fn test_invalid_filesets_looking_like_filepaths() {
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_ok(test_env.env_root(), &["git", "init", "repo"]);
+    let repo_path = test_env.env_root().join("repo");
+
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["file", "show", "abc~"]);
+    insta::assert_snapshot!(stderr, @r#"
+    Error: Failed to parse fileset: Syntax error
+    Caused by:  --> 1:5
+      |
+    1 | abc~
+      |     ^---
+      |
+      = expected `~` or <primary>
+    Hint: Filesets are enabled by default. If you want to match file paths containing characters used in fileset expressions (':', or '~'), escape them, or prefix them with "glob:".
+    "#);
+
+    test_env.add_config(r#"ui.allow-filesets=false"#);
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["file", "show", "abc~"]);
+    insta::assert_snapshot!(stderr, @r#"
+    Error: No such path: abc~
+    "#);
+}
+
 #[test]
 fn test_broken_repo_structure() {
     let test_env = TestEnvironment::default();