Rename conflict revset to conflicts.

See discussion thread in linked issue.

With this PR, all revset functions in [BUILTIN_FUNCTION_MAP](https://github.com/martinvonz/jj/blob/8d166c764251042287626ab37a1148386cef8371/lib/src/revset.rs#L570)
that return multiple values are either named in plural or named in a difficult-to-misused manner (e.g. `reachable`)

Fixes: #4122

CHANGELOG.md

@@ -77,6 +77,9 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
   commit to commit. It now either follows the flags `--edit|--no-edit` or it
   gets the mode from `ui.movement.edit`.
 
+* `conflict` revset has been renamed to `conflicts`. With this, all revsets that
+  could potentially return multiple results are named in the plural.
+
 ### Deprecations
 
 * `jj untrack` has been renamed to `jj file untrack`.

cli/src/cli_util.rs

@@ -2733,6 +2733,11 @@ pub struct RevisionArg(Cow<'static, str>);
 impl RevisionArg {
     /// The working-copy symbol, which is the default of the most commands.
     pub const AT: Self = RevisionArg(Cow::Borrowed("@"));
+
+    pub warn_deprecated(&self) {
+        let _ = Self(self);
+    }
+
 }
 
 impl From<String> for RevisionArg {

docs/revsets.md

@@ -296,7 +296,7 @@ given [string pattern](#string-patterns).
   For example, `diff_contains("TODO", "src")` will search revisions where "TODO"
   is added to or removed from files under "src".
 
-* `conflict()`: Commits with conflicts.
+* `conflicts()`: 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 bookmark name.)

lib/src/revset.rs

@@ -787,6 +787,10 @@ static BUILTIN_FUNCTION_MAP: Lazy<HashMap<&'static str, RevsetFunction>> = Lazy:
         function.expect_no_arguments()?;
         Ok(RevsetExpression::filter(RevsetFilterPredicate::HasConflict))
     });
+    map.insert("conflicts", |function, _context| {
+        function.expect_no_arguments()?;
+        Ok(RevsetExpression::filter(RevsetFilterPredicate::HasConflict))
+    });
     map.insert("present", |function, context| {
         let [arg] = function.expect_exact_arguments()?;
         let expression = lower_expression(arg, context)?;

lib/tests/test_revset.rs

@@ -3451,7 +3451,7 @@ fn test_evaluate_expression_conflict() {
 
     // Only commit4 has a conflict
     assert_eq!(
-        resolve_commit_ids(mut_repo, "conflict()"),
+        resolve_commit_ids(mut_repo, "conflicts()"),
         vec![commit4.id().clone()]
     );
 }