From 0d17ddc7e7fb756cb64eb1f9efac85a25999ac7a Mon Sep 17 00:00:00 2001
From: Scott Taylor <scott.g.taylor@jpmchase.com>
Date: Sat, 16 Nov 2024 11:25:30 -0600
Subject: [PATCH] conflicts: add "snapshot" conflict marker style

Adds a new "snapshot" conflict marker style which returns a series of
snapshots, similar to Git's "diff3" conflict style. The "snapshot"
option uses a subset of the conflict hunk headers as the "diff" option
(it just doesn't use "%%%%%%%"), meaning that the two options are
trivially compatible with each other (i.e. a file materialized with
"snapshot" can be parsed with "diff" and vice versa).

Example of "snapshot" conflict markers:

```
<<<<<<< Conflict 1 of 1
+++++++ Contents of side #1
fn example(word: String) {
    println!("word is {word}");
------- Contents of base
fn example(w: String) {
    println!("word is {w}");
+++++++ Contents of side #2
fn example(w: &str) {
    println!("word is {w}");
>>>>>>> Conflict 1 of 1 ends
}
```
---
 CHANGELOG.md               |  2 ++
 cli/src/config-schema.json |  3 ++-
 lib/src/conflicts.rs       | 13 ++++++++++++-
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7b74375d52..568458d42b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -44,6 +44,8 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 * New `ui.conflict-marker-style` config option to change how conflicts are
   materialized in the working copy. The default option ("diff") renders
   conflicts as a snapshot with a list of diffs to apply to the snapshot.
+  The new "snapshot" option just renders conflicts as a series of snapshots,
+  showing each side of the conflict and the base(s).
 
 ### Fixed bugs
 
diff --git a/cli/src/config-schema.json b/cli/src/config-schema.json
index b9c347018c..0468e95c35 100644
--- a/cli/src/config-schema.json
+++ b/cli/src/config-schema.json
@@ -163,7 +163,8 @@
                     "type": "string",
                     "description": "Conflict marker style to use when materializing conflicts in the working copy",
                     "enum": [
-                        "diff"
+                        "diff",
+                        "snapshot"
                     ],
                     "default": "diff"
                 }
diff --git a/lib/src/conflicts.rs b/lib/src/conflicts.rs
index df2cde1b72..f5f1fb9016 100644
--- a/lib/src/conflicts.rs
+++ b/lib/src/conflicts.rs
@@ -140,6 +140,8 @@ pub async fn extract_as_single_hunk(
 pub enum ConflictMarkerStyle {
     /// Style which shows a snapshot and a series of diffs to apply
     Diff,
+    /// Style which shows a snapshot for each base and side
+    Snapshot,
 }
 
 /// A type similar to `MergedTreeValue` but with associated data to include in
@@ -241,7 +243,7 @@ async fn materialize_tree_value_no_access_denied(
 
 pub fn materialize_merge_result(
     single_hunk: &Merge<BString>,
-    _conflict_marker_style: ConflictMarkerStyle,
+    conflict_marker_style: ConflictMarkerStyle,
     output: &mut dyn Write,
 ) -> std::io::Result<()> {
     let merge_result = files::merge(single_hunk);
@@ -280,6 +282,15 @@ pub fn materialize_merge_result(
                             write_base(&base_str, left, output)?;
                             continue;
                         };
+
+                        // For snapshot style, always emit sides and bases separately
+                        if conflict_marker_style == ConflictMarkerStyle::Snapshot {
+                            write_side(add_index, right1, output)?;
+                            write_base(&base_str, left, output)?;
+                            add_index += 1;
+                            continue;
+                        }
+
                         let diff1 = Diff::by_line([&left, &right1]).hunks().collect_vec();
                         // Check if the diff against the next positive term is better. Since
                         // we want to preserve the order of the terms, we don't match against