revset: add working_copies() function

It includes the working copy commit of every workspace of the repo.

Implements #3384

lib/src/revset.rs

@@ -275,6 +275,7 @@ pub const GENERATION_RANGE_EMPTY: Range<u64> = 0..0;
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub enum RevsetCommitRef {
     WorkingCopy(WorkspaceId),
+    WorkingCopies(),
     Symbol(String),
     RemoteSymbol {
         name: String,
@@ -371,6 +372,10 @@ impl RevsetExpression {
         )))
     }
 
+    pub fn working_copies() -> Rc<RevsetExpression> {
+        Rc::new(RevsetExpression::CommitRef(RevsetCommitRef::WorkingCopies()))
+    }
+
     pub fn symbol(value: String) -> Rc<RevsetExpression> {
         Rc::new(RevsetExpression::CommitRef(RevsetCommitRef::Symbol(value)))
     }
@@ -1157,6 +1162,10 @@ static BUILTIN_FUNCTION_MAP: Lazy<HashMap<&'static str, RevsetFunction>> = Lazy:
         expect_no_arguments(name, arguments_pair)?;
         Ok(RevsetExpression::all())
     });
+    map.insert("working_copies", |name, arguments_pair, _state| {
+        expect_no_arguments(name, arguments_pair)?;
+        Ok(RevsetExpression::working_copies())
+    });
     map.insert("heads", |name, arguments_pair, state| {
         let arg = expect_one_argument(name, arguments_pair)?;
         let candidates = parse_expression_rule(arg.into_inner(), state)?;
@@ -2139,6 +2148,15 @@ fn resolve_commit_ref(
                 })
             }
         }
+        RevsetCommitRef::WorkingCopies() => {
+            let wc_commits: Vec<CommitId> = repo
+                .view()
+                .wc_commit_ids()
+                .iter()
+                .map(|(_, v)| v.clone())
+                .collect();
+            Ok(wc_commits)
+        }
         RevsetCommitRef::VisibleHeads => Ok(repo.view().heads().iter().cloned().collect_vec()),
         RevsetCommitRef::Root => Ok(vec![repo.store().root_commit_id().clone()]),
         RevsetCommitRef::Branches(pattern) => {