merge: add Merge::num_sides()

An alternative name for it would be `arity()`, but `num_sides()`
probably more clearly says that it's not about the number of removes
or the total number of terms.

cli/src/commands/mod.rs

@@ -2787,7 +2787,7 @@ fn print_conflicted_paths(
         .map(|p| format!("{:width$}", p, width = max_path_len.min(32) + 3));
 
     for ((_, conflict), formatted_path) in std::iter::zip(conflicts.iter(), formatted_paths) {
-        let sides = conflict.adds().len();
+        let sides = conflict.num_sides();
         let n_adds = conflict.adds().iter().flatten().count();
         let deletions = sides - n_adds;
 

cli/src/merge_tools/mod.rs

@@ -98,10 +98,10 @@ pub fn run_mergetool(
         )
     })?;
     // We only support conflicts with 2 sides (3-way conflicts)
-    if file_merge.adds().len() > 2 {
+    if file_merge.num_sides() > 2 {
         return Err(ConflictResolveError::ConflictTooComplicated {
             path: repo_path.clone(),
-            sides: file_merge.adds().len(),
+            sides: file_merge.num_sides(),
         });
     };
     let content = extract_as_single_hunk(&file_merge, tree.store(), repo_path);

lib/src/conflicts.rs

@@ -206,7 +206,7 @@ pub fn parse_conflict(input: &[u8], num_sides: usize) -> Option<Vec<Merge<Conten
         } else if conflict_start.is_some() && line == CONFLICT_END_LINE {
             let conflict_body = &input[conflict_start.unwrap() + CONFLICT_START_LINE.len()..pos];
             let hunk = parse_conflict_hunk(conflict_body);
-            if hunk.adds().len() == num_sides {
+            if hunk.num_sides() == num_sides {
                 let resolved_slice = &input[resolved_start..conflict_start.unwrap()];
                 if !resolved_slice.is_empty() {
                     hunks.push(Merge::resolved(ContentHunk(resolved_slice.to_vec())));
@@ -314,7 +314,7 @@ pub fn update_from_content(
 
     let mut removed_content = vec![vec![]; file_ids.removes().len()];
     let mut added_content = vec![vec![]; file_ids.adds().len()];
-    let Some(hunks) = parse_conflict(content, file_ids.adds().len()) else {
+    let Some(hunks) = parse_conflict(content, file_ids.num_sides()) else {
         // Either there are no self markers of they don't have the expected arity
         let file_id = store.write_file(path, &mut &content[..])?;
         return Ok(Merge::normal(file_id));

lib/src/merge.rs

@@ -154,6 +154,11 @@ impl<T> Merge<T> {
         &self.adds
     }
 
+    /// The number of positive terms in the conflict.
+    pub fn num_sides(&self) -> usize {
+        self.adds.len()
+    }
+
     /// Whether this merge is resolved. Does not resolve trivial merges.
     pub fn is_resolved(&self) -> bool {
         self.removes.is_empty()

lib/tests/test_conflicts.rs

@@ -299,7 +299,7 @@ line 5 right
 
     // The first add should always be from the left side
     insta::assert_debug_snapshot!(
-        parse_conflict(materialized.as_bytes(), conflict.adds().len()),
+        parse_conflict(materialized.as_bytes(), conflict.num_sides()),
         @r###"
     Some(
         [