conflict_labels: add functions with defaults for missing labels

This removes the special case for using "base" instead of "base #1" when
there's only one base, but since all new conflicts will have labels,
this should be fine.

cli/tests/test_evolog_command.rs

@@ -457,7 +457,7 @@ fn test_evolog_squash() {
     │ │     1     : <<<<<<< conflict 1 of 1
     │ │     2     : +++++++ side #1
     │ │     3    1: squashed 1
-    │ │     4     : %%%%%%% diff from: base
+    │ │     4     : %%%%%%% diff from: base #1
     │ │     5    1: \\\\\\\        to: side #2
     │ │     6     : +third
     │ │     7     : >>>>>>> conflict 1 of 1 ends
@@ -489,7 +489,7 @@ fn test_evolog_squash() {
     │ │  -- operation 65c81703100d squash commits into 5878cbe03cdf599c9353e5a1a52a01f4c5e0e0fa
     │ │  Modified commit description:
     │ │     1     : <<<<<<< conflict 1 of 1
-    │ │     2     : %%%%%%% diff from: base
+    │ │     2     : %%%%%%% diff from: base #1
     │ │     3     : \\\\\\\        to: side #1
     │ │     4     : +first
     │ │     5     : +++++++ side #2

lib/src/conflict_labels.rs

@@ -14,6 +14,7 @@
 
 //! Labels for conflicted trees.
 
+use std::borrow::Cow;
 use std::fmt;
 
 use crate::merge::Merge;
@@ -94,6 +95,12 @@ impl ConflictLabels {
             .map(String::as_str)
     }
 
+    /// Get the label for a side at an index or a default label.
+    pub fn get_add_or_default(&self, add_index: usize) -> Cow<'_, str> {
+        self.get_add(add_index)
+            .map_or_else(|| format!("side #{}", add_index + 1).into(), Cow::from)
+    }
+
     /// Get the label for a base at an index.
     pub fn get_remove(&self, remove_index: usize) -> Option<&str> {
         self.labels
@@ -102,6 +109,21 @@ impl ConflictLabels {
             .map(String::as_str)
     }
 
+    /// Get the label for a base at an index or a default label.
+    pub fn get_remove_or_default(&self, remove_index: usize) -> Cow<'_, str> {
+        self.get_remove(remove_index)
+            .map_or_else(|| format!("base #{}", remove_index + 1).into(), Cow::from)
+    }
+
+    /// Get the label at a given index (alternating adds and removes).
+    pub fn get_or_default(&self, index: usize) -> Cow<'_, str> {
+        if index.is_multiple_of(2) {
+            self.get_add_or_default(index / 2)
+        } else {
+            self.get_remove_or_default(index / 2)
+        }
+    }
+
     /// Simplify a merge with the same number of sides while preserving the
     /// conflict labels corresponding to each side of the merge.
     pub fn simplify_with<T: PartialEq + Clone>(&self, merge: &Merge<T>) -> (Self, Merge<T>) {

lib/src/conflicts.rs

@@ -50,6 +50,7 @@ use crate::files;
 use crate::files::MergeResult;
 use crate::merge::Diff;
 use crate::merge::Merge;
+use crate::merge::MergeBuilder;
 use crate::merge::MergedTreeValue;
 use crate::merge::SameChange;
 use crate::repo_path::RepoPath;
@@ -574,31 +575,15 @@ struct HunkTerm {
 }
 
 fn build_hunk_sides(hunk: Merge<BString>, labels: &ConflictLabels) -> Merge<HunkTerm> {
-    let (removes, adds) = hunk.into_removes_adds();
-    let num_bases = removes.len();
-    let removes = removes.enumerate().map(|(base_index, contents)| {
-        let label = labels
-            .get_remove(base_index)
-            .map(|label| label.to_owned())
-            .unwrap_or_else(|| {
-                // The vast majority of conflicts one actually tries to resolve manually have 1
-                // base.
-                if num_bases == 1 {
-                    "base".to_string()
-                } else {
-                    format!("base #{}", base_index + 1)
-                }
-            });
-        HunkTerm { contents, label }
-    });
-    let adds = adds.enumerate().map(|(add_index, contents)| {
-        let label = labels.get_add(add_index).map_or_else(
-            || format!("side #{}", add_index + 1),
-            |label| label.to_owned(),
-        );
-        HunkTerm { contents, label }
-    });
-    let mut hunk_terms = Merge::from_removes_adds(removes, adds);
+    let mut hunk_terms = hunk
+        .into_iter()
+        .enumerate()
+        .map(|(index, contents)| HunkTerm {
+            contents,
+            label: labels.get_or_default(index).into_owned(),
+        })
+        .collect::<MergeBuilder<_>>()
+        .build();
     for term in &mut hunk_terms {
         // We don't add the no eol comment if the side is empty.
         if term.contents.last().is_some_and(|ch| *ch != b'\n') {

lib/tests/test_conflicts.rs

@@ -95,7 +95,7 @@ fn test_materialize_conflict_basic() {
     left 3.1
     left 3.2
     left 3.3
-    %%%%%%% diff from: base
+    %%%%%%% diff from: base #1
     \\\\\\\        to: side #2
     -line 3
     +right 3.1
@@ -116,7 +116,7 @@ fn test_materialize_conflict_basic() {
     line 1
     line 2
     <<<<<<< conflict 1 of 1
-    %%%%%%% diff from: base
+    %%%%%%% diff from: base #1
     \\\\\\\        to: side #1
     -line 3
     +right 3.1
@@ -144,7 +144,7 @@ fn test_materialize_conflict_basic() {
     left 3.1
     left 3.2
     left 3.3
-    ------- base
+    ------- base #1
     line 3
     +++++++ side #2
     right 3.1
@@ -167,7 +167,7 @@ fn test_materialize_conflict_basic() {
     left 3.1
     left 3.2
     left 3.3
-    ||||||| base
+    ||||||| base #1
     line 3
     =======
     right 3.1
@@ -531,15 +531,15 @@ fn test_materialize_parse_roundtrip() {
     +++++++ side #1
     line 1 left
     line 2 left
-    %%%%%%% diff from: base
+    %%%%%%% diff from: base #1
     \\\\\\\        to: side #2
     -line 1
     +line 1 right
      line 2
     >>>>>>> conflict 1 of 2 ends
     line 3
     <<<<<<< conflict 2 of 2
-    %%%%%%% diff from: base
+    %%%%%%% diff from: base #1
     \\\\\\\        to: side #1
      line 4
     -line 5
@@ -659,7 +659,7 @@ fn test_materialize_conflict_no_newlines_at_eof() {
     insta::assert_snapshot!(materialized.to_owned() + "[EOF]",
         @r"
     <<<<<<< conflict 1 of 1
-    %%%%%%% diff from: base (no terminating newline)
+    %%%%%%% diff from: base #1 (no terminating newline)
     \\\\\\\        to: side #1
     -base
     +
@@ -741,7 +741,7 @@ fn test_materialize_conflict_modify_delete() {
     <<<<<<< conflict 1 of 1
     +++++++ side #1
     modified
-    %%%%%%% diff from: base
+    %%%%%%% diff from: base #1
     \\\\\\\        to: side #2
     -line 3
     >>>>>>> conflict 1 of 1 ends
@@ -759,7 +759,7 @@ fn test_materialize_conflict_modify_delete() {
     line 1
     line 2
     <<<<<<< conflict 1 of 1
-    %%%%%%% diff from: base
+    %%%%%%% diff from: base #1
     \\\\\\\        to: side #1
     -line 3
     +++++++ side #2
@@ -777,7 +777,7 @@ fn test_materialize_conflict_modify_delete() {
     );
     insta::assert_snapshot!(&materialize_conflict_string(store, path, &conflict, ConflictMarkerStyle::Diff), @r"
     <<<<<<< conflict 1 of 1
-    %%%%%%% diff from: base
+    %%%%%%% diff from: base #1
     \\\\\\\        to: side #1
      line 1
      line 2
@@ -1880,7 +1880,7 @@ fn test_update_conflict_from_content_simplified_conflict() {
         materialized,
         @r"
     <<<<<<< conflict 1 of 2
-    %%%%%%% diff from: base
+    %%%%%%% diff from: base #1
     \\\\\\\        to: side #1
     -line 1
     +left 1
@@ -1889,7 +1889,7 @@ fn test_update_conflict_from_content_simplified_conflict() {
     >>>>>>> conflict 1 of 2 ends
     line 2
     <<<<<<< conflict 2 of 2
-    %%%%%%% diff from: base
+    %%%%%%% diff from: base #1
     \\\\\\\        to: side #1
     -line 3
     +left 3
@@ -1992,7 +1992,7 @@ fn test_update_conflict_from_content_with_long_markers() {
     <<<<<<<<<<<<<<<< conflict 1 of 2
     ++++++++++++++++ side #1
     <<<< left 1
-    ---------------- base
+    ---------------- base #1
     line 1
     ++++++++++++++++ side #2
     >>>>>>> right 1
@@ -2001,7 +2001,7 @@ fn test_update_conflict_from_content_with_long_markers() {
     <<<<<<<<<<<<<<<< conflict 2 of 2
     ++++++++++++++++ side #1
     <<<<<<<<<<<< left 3
-    ---------------- base
+    ---------------- base #1
     line 3
     ++++++++++++++++ side #2
     >>>>>>>>>>>> right 3
@@ -2094,7 +2094,7 @@ fn test_update_conflict_from_content_with_long_markers() {
     <<<<<<<<<<< conflict 1 of 1
     +++++++++++ side #1
     <<<< left 1
-    ----------- base
+    ----------- base #1
     line 1
     +++++++++++ side #2
     >>>>>>> right 1
@@ -2127,7 +2127,7 @@ fn test_update_conflict_from_content_no_eol() {
         @r"
     line 1
     <<<<<<< conflict 1 of 2
-    %%%%%%% diff from: base
+    %%%%%%% diff from: base #1
     \\\\\\\        to: side #1
     -line 2
     +line 2 left
@@ -2136,7 +2136,7 @@ fn test_update_conflict_from_content_no_eol() {
     >>>>>>> conflict 1 of 2 ends
     line 3
     <<<<<<< conflict 2 of 2
-    %%%%%%% diff from: base (no terminating newline)
+    %%%%%%% diff from: base #1 (no terminating newline)
     \\\\\\\        to: side #1
      base
     +left
@@ -2167,7 +2167,7 @@ fn test_update_conflict_from_content_no_eol() {
     <<<<<<< conflict 1 of 2
     +++++++ side #1
     line 2 left
-    ------- base
+    ------- base #1
     line 2
     +++++++ side #2
     line 2 right
@@ -2178,7 +2178,7 @@ fn test_update_conflict_from_content_no_eol() {
     base
     left
 
-    ------- base (no terminating newline)
+    ------- base #1 (no terminating newline)
     base
     +++++++ side #2 (no terminating newline)
     right
@@ -2205,7 +2205,7 @@ fn test_update_conflict_from_content_no_eol() {
     line 1
     <<<<<<< side #1
     line 2 left
-    ||||||| base
+    ||||||| base #1
     line 2
     =======
     line 2 right
@@ -2215,7 +2215,7 @@ fn test_update_conflict_from_content_no_eol() {
     base
     left
 
-    ||||||| base (no terminating newline)
+    ||||||| base #1 (no terminating newline)
     base
     =======
     right
@@ -2338,7 +2338,7 @@ fn test_update_conflict_from_content_only_no_eol_change() {
     <<<<<<< conflict 1 of 1
     +++++++ side #1 (no terminating newline)
     line 2
-    %%%%%%% diff from: base
+    %%%%%%% diff from: base #1
     \\\\\\\        to: side #2
     +line 2
 
@@ -2416,7 +2416,7 @@ fn test_update_from_content_malformed_conflict() {
     insta::assert_snapshot!(materialized, @r"
     line 1
     <<<<<<< conflict 1 of 2
-    %%%%%%% diff from: base
+    %%%%%%% diff from: base #1
     \\\\\\\        to: side #1
     -line 2
     +line 2 left
@@ -2425,7 +2425,7 @@ fn test_update_from_content_malformed_conflict() {
     >>>>>>> conflict 1 of 2 ends
     line 3
     <<<<<<< conflict 2 of 2
-    %%%%%%% diff from: base
+    %%%%%%% diff from: base #1
     \\\\\\\        to: side #1
     -line 4
     +line 4 left