revsets: accept quoted symbol names

Git refs with names containing e.g "-" are currently not accepted
symbol names, and I don't plan to change the grammar to accept
them. Instead, let's have the user quote symbol names containing
unusual characters. That way we can keep these symbols reserved for
revset operators.

With this patch the user can do e.g. `jj diff -r '"v2.9.0-rc2"'`.

lib/src/revset.pest

@@ -12,7 +12,11 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-symbol = @{ (ASCII_ALPHANUMERIC | "@" | "/" | ".")+ }
+identifier = @{ (ASCII_ALPHANUMERIC | "@" | "/" | ".")+ } 
+symbol = {
+  identifier
+  | literal_string
+}
 literal_string = { "\"" ~ (!"\"" ~ ANY)+ ~ "\"" }
 whitespace = _{ " " }
 

lib/src/revset.rs

@@ -233,13 +233,34 @@ fn parse_primary_rule(mut pairs: Pairs<Rule>) -> Result<RevsetExpression, Revset
             let argument_pairs = pairs.next().unwrap().into_inner();
             parse_function_expression(name, argument_pairs)
         }
-        Rule::symbol => Ok(RevsetExpression::Symbol(first.as_str().to_owned())),
+        Rule::symbol => parse_symbol_rule(first.into_inner()),
         _ => {
             panic!("unxpected revset parse rule: {:?}", first.as_str());
         }
     }
 }
 
+fn parse_symbol_rule(mut pairs: Pairs<Rule>) -> Result<RevsetExpression, RevsetParseError> {
+    let first = pairs.next().unwrap();
+    match first.as_rule() {
+        Rule::identifier => Ok(RevsetExpression::Symbol(first.as_str().to_owned())),
+        Rule::literal_string => {
+            return Ok(RevsetExpression::Symbol(
+                first
+                    .as_str()
+                    .strip_prefix('"')
+                    .unwrap()
+                    .strip_suffix('"')
+                    .unwrap()
+                    .to_owned(),
+            ));
+        }
+        _ => {
+            panic!("unxpected symbol parse rule: {:?}", first.as_str());
+        }
+    }
+}
+
 fn parse_function_expression(
     name: String,
     mut argument_pairs: Pairs<Rule>,
@@ -858,6 +879,11 @@ mod tests {
             parse("(foo)"),
             Ok(RevsetExpression::Symbol("foo".to_string()))
         );
+        // Parse a quoted symbol
+        assert_eq!(
+            parse("\"foo\""),
+            Ok(RevsetExpression::Symbol("foo".to_string()))
+        );
         // Parse the "parents" operator
         assert_eq!(
             parse(":@"),