revset: add a revset function for finding commits with conflicts

This adds `conflict()` revset that selects commits with conflicts. We
may want to extend it later to consider only conflicts at certain
paths.

CHANGELOG.md

@@ -65,6 +65,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * Added `latest(x[, n])` revset function to select the latest `n` commits.
 
+* Added `conflict()` revset function to select commits with conflicts.
+
 * `jj squash` AKA `jj amend` now accepts a `--message` option to set the
   description of the squashed commit on the command-line.
 

docs/revsets.md

@@ -120,6 +120,7 @@ revsets (expressions) as arguments.
   user modifications and `root`.
 * `file(pattern..)`: Commits modifying the paths specified by the `pattern..`.
   Paths are relative to the directory `jj` was invoked from.
+* `conflict()`: Commits with conflicts.
 * `present(x)`: Same as `x`, but evaluated to `none()` if any of the commits
   in `x` doesn't exist (e.g. is an unknown branch name.)
 

lib/src/default_revset_engine.rs

@@ -944,6 +944,10 @@ fn build_predicate_fn<'index>(
                 has_diff_from_parent(&store, index, entry, matcher.as_ref())
             })
         }
+        RevsetFilterPredicate::HasConflict => pure_predicate_fn(move |entry| {
+            let commit = store.get_commit(&entry.commit_id()).unwrap();
+            commit.tree().has_conflict()
+        }),
     }
 }
 

lib/src/revset.rs

@@ -205,6 +205,8 @@ pub enum RevsetFilterPredicate {
     Committer(String),
     /// Commits modifying the paths specified by the pattern.
     File(Option<Vec<RepoPath>>), // TODO: embed matcher expression?
+    /// Commits with conflicts
+    HasConflict,
 }
 
 #[derive(Debug, PartialEq, Eq, Clone)]
@@ -928,6 +930,10 @@ static BUILTIN_FUNCTION_MAP: Lazy<HashMap<&'static str, RevsetFunction>> = Lazy:
             ))
         }
     });
+    map.insert("conflict", |name, arguments_pair, _state| {
+        expect_no_arguments(name, arguments_pair)?;
+        Ok(RevsetExpression::filter(RevsetFilterPredicate::HasConflict))
+    });
     map.insert("present", |name, arguments_pair, state| {
         let arg = expect_one_argument(name, arguments_pair)?;
         let expression = parse_expression_rule(arg.into_inner(), state)?;

lib/tests/test_revset.rs

@@ -29,6 +29,7 @@ use jujutsu_lib::revset::{
     RevsetResolutionError, RevsetWorkspaceContext,
 };
 use jujutsu_lib::settings::GitSettings;
+use jujutsu_lib::tree::merge_trees;
 use jujutsu_lib::workspace::Workspace;
 use test_case::test_case;
 use testutils::{
@@ -2142,6 +2143,49 @@ fn test_evaluate_expression_file(use_git: bool) {
     );
 }
 
+#[test_case(false ; "local backend")]
+#[test_case(true ; "git backend")]
+fn test_evaluate_expression_conflict(use_git: bool) {
+    let settings = testutils::user_settings();
+    let test_workspace = TestWorkspace::init(&settings, use_git);
+    let repo = &test_workspace.repo;
+
+    let mut tx = repo.start_transaction(&settings, "test");
+    let mut_repo = tx.mut_repo();
+
+    // Create a few trees, including one with a conflict in `file1`
+    let file_path1 = RepoPath::from_internal_string("file1");
+    let file_path2 = RepoPath::from_internal_string("file2");
+    let tree1 = testutils::create_tree(repo, &[(&file_path1, "1"), (&file_path2, "1")]);
+    let tree2 = testutils::create_tree(repo, &[(&file_path1, "2"), (&file_path2, "2")]);
+    let tree3 = testutils::create_tree(repo, &[(&file_path1, "3"), (&file_path2, "1")]);
+    let tree_id4 = merge_trees(&tree2, &tree1, &tree3).unwrap();
+    let tree4 = mut_repo
+        .store()
+        .get_tree(&RepoPath::root(), &tree_id4)
+        .unwrap();
+
+    let mut create_commit = |parent_ids, tree_id| {
+        mut_repo
+            .new_commit(&settings, parent_ids, tree_id)
+            .write()
+            .unwrap()
+    };
+    let commit1 = create_commit(
+        vec![repo.store().root_commit_id().clone()],
+        tree1.id().clone(),
+    );
+    let commit2 = create_commit(vec![commit1.id().clone()], tree2.id().clone());
+    let commit3 = create_commit(vec![commit2.id().clone()], tree3.id().clone());
+    let commit4 = create_commit(vec![commit3.id().clone()], tree4.id().clone());
+
+    // Only commit4 has a conflict
+    assert_eq!(
+        resolve_commit_ids(mut_repo, "conflict()"),
+        vec![commit4.id().clone()]
+    );
+}
+
 #[test]
 fn test_reverse_graph_iterator() {
     let settings = testutils::user_settings();

testing/bench-revsets-git.txt

@@ -43,6 +43,7 @@ tags()+
 # Filter that doesn't read commit object
 merges()
 ~merges()
-# Files are unbearably slow, so only filter within small set
+# These are unbearably slow, so only filter within small set
 file(Makefile) & v1.0.0..v1.2.0
 empty() & v1.0.0..v1.2.0
+conflict() & v1.0.0..v1.2.0