conflicts: extract header output into separate functions

This will make it easier to add separate logic for "snapshot" style
conflict markers in the next commit.

lib/src/conflicts.rs

@@ -301,9 +301,7 @@ fn materialize_conflict_hunks(
                 let Some(right1) = hunk.get_add(add_index) else {
                     // If we have no more positive terms, emit the remaining negative
                     // terms as snapshots.
-                    output.write_all(CONFLICT_MINUS_LINE)?;
-                    output.write_all(format!(" Contents of {base_str}\n").as_bytes())?;
-                    output.write_all(left)?;
+                    write_base(&base_str, left, output)?;
                     continue;
                 };
                 let diff1 = Diff::by_line([&left, &right1]).hunks().collect_vec();
@@ -316,35 +314,20 @@ fn materialize_conflict_hunks(
                         // If the next positive term is a better match, emit
                         // the current positive term as a snapshot and the next
                         // positive term as a diff.
-                        output.write_all(CONFLICT_PLUS_LINE)?;
-                        output.write_all(
-                            format!(" Contents of side #{}\n", add_index + 1).as_bytes(),
-                        )?;
-                        output.write_all(right1)?;
-                        output.write_all(CONFLICT_DIFF_LINE)?;
-                        output.write_all(
-                            format!(" Changes from {base_str} to side #{}\n", add_index + 2)
-                                .as_bytes(),
-                        )?;
-                        write_diff_hunks(&diff2, output)?;
+                        write_side(add_index, right1, output)?;
+                        write_diff(&base_str, add_index + 1, &diff2, output)?;
                         add_index += 2;
                         continue;
                     }
                 }
 
-                output.write_all(CONFLICT_DIFF_LINE)?;
-                output.write_all(
-                    format!(" Changes from {base_str} to side #{}\n", add_index + 1).as_bytes(),
-                )?;
-                write_diff_hunks(&diff1, output)?;
+                write_diff(&base_str, add_index, &diff1, output)?;
                 add_index += 1;
             }
 
-            //  Emit the remaining positive terms as snapshots.
+            // Emit the remaining positive terms as snapshots.
             for (add_index, slice) in hunk.adds().enumerate().skip(add_index) {
-                output.write_all(CONFLICT_PLUS_LINE)?;
-                output.write_all(format!(" Contents of side #{}\n", add_index + 1).as_bytes())?;
-                output.write_all(slice)?;
+                write_side(add_index, slice, output)?;
             }
             output.write_all(CONFLICT_END_LINE)?;
             output.write_all(
@@ -355,6 +338,33 @@ fn materialize_conflict_hunks(
     Ok(())
 }
 
+/// Write a positive snapshot (side) of a conflict
+fn write_side(add_index: usize, data: &[u8], output: &mut dyn Write) -> std::io::Result<()> {
+    output.write_all(CONFLICT_PLUS_LINE)?;
+    output.write_all(format!(" Contents of side #{}\n", add_index + 1).as_bytes())?;
+    output.write_all(data)
+}
+
+/// Write a negative snapshot (base) of a conflict
+fn write_base(base_str: &str, data: &[u8], output: &mut dyn Write) -> std::io::Result<()> {
+    output.write_all(CONFLICT_MINUS_LINE)?;
+    output.write_all(format!(" Contents of {base_str}\n").as_bytes())?;
+    output.write_all(data)
+}
+
+/// Write a diff from a negative term to a positive term
+fn write_diff(
+    base_str: &str,
+    add_index: usize,
+    diff: &[DiffHunk],
+    output: &mut dyn Write,
+) -> std::io::Result<()> {
+    output.write_all(CONFLICT_DIFF_LINE)?;
+    output
+        .write_all(format!(" Changes from {base_str} to side #{}\n", add_index + 1).as_bytes())?;
+    write_diff_hunks(diff, output)
+}
+
 fn diff_size(hunks: &[DiffHunk]) -> usize {
     hunks
         .iter()