copy-tracking: add support for diff --git

CHANGELOG.md

@@ -15,7 +15,7 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 ### New features
 
 * The following diff formats now include information about copies and moves:
-  `--color-words`, `--stat`, `--summary`, `--types`
+  `--color-words`, `--git`, `--stat`, `--summary`, `--types`
 
 * A tilde (`~`) at the start of the path will now be expanded to the user's home
   directory when configuring a `signing.key` for SSH commit signing.

cli/src/commit_templater.rs

@@ -1366,8 +1366,20 @@ fn builtin_tree_diff_methods<'repo>() -> CommitTemplateBuildMethodFnMap<'repo, T
         let template = (self_property, context_property)
             .map(|(diff, context)| {
                 let context = context.unwrap_or(diff_util::DEFAULT_CONTEXT_LINES);
-                diff.into_formatted(move |formatter, store, tree_diff| {
-                    diff_util::show_git_diff(formatter, store, tree_diff, context)
+                // TODO: don't pass separate copies of from_tree/to_tree/matcher
+                let from_tree = diff.from_tree.clone();
+                let to_tree = diff.to_tree.clone();
+                let matcher = diff.matcher.clone();
+                diff.into_formatted(move |formatter, store, _tree_diff| {
+                    diff_util::show_git_diff(
+                        formatter,
+                        store,
+                        &from_tree,
+                        &to_tree,
+                        matcher.as_ref(),
+                        &Default::default(), // TODO: real copy tracking
+                        context,
+                    )
                 })
             })
             .into_template();
@@ -1405,7 +1417,7 @@ fn builtin_tree_diff_methods<'repo>() -> CommitTemplateBuildMethodFnMap<'repo, T
                             &from_tree,
                             &to_tree,
                             matcher.as_ref(),
-                            &Default::default(),
+                            &Default::default(), // TODO: real copy tracking
                         )
                     })
                 })

cli/src/diff_util.rs

@@ -307,9 +307,15 @@ impl<'a> DiffRenderer<'a> {
                     show_names(formatter, tree_diff, path_converter)?;
                 }
                 DiffFormat::Git { context } => {
-                    let no_copy_tracking = Default::default();
-                    let tree_diff = from_tree.diff_stream(to_tree, matcher, &no_copy_tracking);
-                    show_git_diff(formatter, store, tree_diff, *context)?;
+                    show_git_diff(
+                        formatter,
+                        store,
+                        from_tree,
+                        to_tree,
+                        matcher,
+                        copy_records,
+                        *context,
+                    )?;
                 }
                 DiffFormat::ColorWords { context } => {
                     let tree_diff = from_tree.diff_stream(to_tree, matcher, copy_records);
@@ -1097,23 +1103,40 @@ fn show_unified_diff_hunks(
 pub fn show_git_diff(
     formatter: &mut dyn Formatter,
     store: &Store,
-    tree_diff: TreeDiffStream,
+    from_tree: &MergedTree,
+    to_tree: &MergedTree,
+    matcher: &dyn Matcher,
+    copy_records: &CopyRecords,
     num_context_lines: usize,
 ) -> Result<(), DiffRenderError> {
+    let tree_diff = from_tree.diff_stream(to_tree, matcher, copy_records);
     let mut diff_stream = materialized_diff_stream(store, tree_diff);
+    let copied_sources = collect_copied_sources(copy_records, matcher);
+
     async {
         while let Some(MaterializedTreeDiffEntry {
-            source: _, // TODO handle copy tracking
-            target: path,
+            source: left_path,
+            target: right_path,
             value: diff,
         }) = diff_stream.next().await
         {
-            let path_string = path.as_internal_file_string();
+            let left_path_string = left_path.as_internal_file_string();
+            let right_path_string = right_path.as_internal_file_string();
             let (left_value, right_value) = diff?;
-            let left_part = git_diff_part(&path, left_value)?;
-            let right_part = git_diff_part(&path, right_value)?;
+
+            let left_part = git_diff_part(&left_path, left_value)?;
+            let right_part = git_diff_part(&right_path, right_value)?;
+
+            // Skip the "delete" entry when there is a rename.
+            if right_part.mode.is_none() && copied_sources.contains(left_path.as_ref()) {
+                continue;
+            }
+
             formatter.with_label("file_header", |formatter| {
-                writeln!(formatter, "diff --git a/{path_string} b/{path_string}")?;
+                writeln!(
+                    formatter,
+                    "diff --git a/{left_path_string} b/{right_path_string}"
+                )?;
                 let left_hash = &left_part.hash;
                 let right_hash = &right_part.hash;
                 match (left_part.mode, right_part.mode) {
@@ -1126,6 +1149,16 @@ pub fn show_git_diff(
                         writeln!(formatter, "index {left_hash}..{right_hash}")?;
                     }
                     (Some(left_mode), Some(right_mode)) => {
+                        if left_path != right_path {
+                            let operation = if to_tree.path_value(&left_path)?.is_absent() {
+                                "rename"
+                            } else {
+                                "copy"
+                            };
+                            // TODO: include similarity index?
+                            writeln!(formatter, "{operation} from {left_path_string}")?;
+                            writeln!(formatter, "{operation} to {right_path_string}")?;
+                        }
                         if left_mode != right_mode {
                             writeln!(formatter, "old mode {left_mode}")?;
                             writeln!(formatter, "new mode {right_mode}")?;
@@ -1138,19 +1171,19 @@ pub fn show_git_diff(
                     }
                     (None, None) => panic!("either left or right part should be present"),
                 }
-                io::Result::Ok(())
+                Ok::<(), DiffRenderError>(())
             })?;
 
             if left_part.content.contents == right_part.content.contents {
                 continue; // no content hunks
             }
 
             let left_path = match left_part.mode {
-                Some(_) => format!("a/{path_string}"),
+                Some(_) => format!("a/{left_path_string}"),
                 None => "/dev/null".to_owned(),
             };
             let right_path = match right_part.mode {
-                Some(_) => format!("b/{path_string}"),
+                Some(_) => format!("b/{right_path_string}"),
                 None => "/dev/null".to_owned(),
             };
             if left_part.content.is_binary || right_part.content.is_binary {

cli/tests/test_acls.rs

@@ -52,7 +52,7 @@ fn test_diff() {
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "--summary"]);
     insta::assert_snapshot!(stdout.replace('\\', "/"), @r###"
     M a-first
-    A added-secret
+    C {a-first => added-secret}
     D deleted-secret
     M dir/secret
     M modified-secret
@@ -61,21 +61,21 @@ fn test_diff() {
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "--types"]);
     insta::assert_snapshot!(stdout.replace('\\', "/"), @r###"
     FF a-first
-    -F added-secret
+    FF {a-first => added-secret}
     F- deleted-secret
     FF dir/secret
     FF modified-secret
     FF z-last
     "###);
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "--stat"]);
     insta::assert_snapshot!(stdout.replace('\\', "/"), @r###"
-    a-first         | 2 +-
-    added-secret    | 1 +
-    deleted-secret  | 1 -
-    dir/secret      | 0
-    modified-secret | 0
-    z-last          | 2 +-
-    6 files changed, 3 insertions(+), 3 deletions(-)
+    a-first                   | 2 +-
+    {a-first => added-secret} | 2 +-
+    deleted-secret            | 1 -
+    dir/secret                | 0
+    modified-secret           | 0
+    z-last                    | 2 +-
+    6 files changed, 3 insertions(+), 4 deletions(-)
     "###);
     let assert = test_env
         .jj_cmd(&repo_path, &["diff", "--git"])