copy-tracking: add support for `diff --git`

CHANGELOG.md

···
 ### 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

···
         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();
···
                             &from_tree,
                             &to_tree,
                             matcher.as_ref(),
-                            &Default::default(),
+                            &Default::default(), // TODO: real copy tracking
                         )
                     })
                 })

cli/src/diff_util.rs

···
                     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);
···
 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) {
···
                         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}")?;
···
                     }
                     (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 {
···
             }
 
             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

···
     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
···
     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
···
     "###);
     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"])

cli/tests/test_diff_command.rs

···
     let repo_path = test_env.env_root().join("repo");
 
     std::fs::write(repo_path.join("file1"), "foo\n").unwrap();
-    std::fs::write(repo_path.join("file2"), "foo\nbaz qux\n").unwrap();
+    std::fs::write(repo_path.join("file2"), "1\n2\n3\n4\n").unwrap();
     test_env.jj_cmd_ok(&repo_path, &["new"]);
     std::fs::remove_file(repo_path.join("file1")).unwrap();
-    std::fs::write(repo_path.join("file2"), "foo\nbar\nbaz quux\n").unwrap();
+    std::fs::write(repo_path.join("file2"), "1\n5\n3\n").unwrap();
     std::fs::write(repo_path.join("file3"), "foo\n").unwrap();
+    std::fs::write(repo_path.join("file4"), "1\n2\n3\n4\n").unwrap();
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff"]);
     insta::assert_snapshot!(stdout, @r###"
     Removed regular file file1:
        1     : foo
     Modified regular file file2:
-       1    1: foo
-            2: bar
-       2    3: baz quxquux
+       1    1: 1
+       2    2: 25
+       3    3: 3
+       4     : 4
     Modified regular file file3 (file1 => file3):
+    Modified regular file file4 (file2 => file4):
     "###);
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "--context=0"]);
···
     Removed regular file file1:
        1     : foo
     Modified regular file file2:
-       1    1: foo
-            2: bar
-       2    3: baz quxquux
+       1    1: 1
+       2    2: 25
+       3    3: 3
+       4     : 4
     Modified regular file file3 (file1 => file3):
+    Modified regular file file4 (file2 => file4):
+        ...
     "###);
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "--color=debug"]);
···
     <<diff header::Removed regular file file1:>>
     <<diff removed line_number::   1>><<diff::     : >><<diff removed token::foo>>
     <<diff header::Modified regular file file2:>>
-    <<diff removed line_number::   1>><<diff:: >><<diff added line_number::   1>><<diff::: foo>>
-    <<diff::     >><<diff added line_number::   2>><<diff::: >><<diff added token::bar>>
-    <<diff removed line_number::   2>><<diff:: >><<diff added line_number::   3>><<diff::: baz >><<diff removed token::qux>><<diff added token::quux>><<diff::>>
+    <<diff removed line_number::   1>><<diff:: >><<diff added line_number::   1>><<diff::: 1>>
+    <<diff removed line_number::   2>><<diff:: >><<diff added line_number::   2>><<diff::: >><<diff removed token::2>><<diff added token::5>><<diff::>>
+    <<diff removed line_number::   3>><<diff:: >><<diff added line_number::   3>><<diff::: 3>>
+    <<diff removed line_number::   4>><<diff::     : >><<diff removed token::4>>
     <<diff header::Modified regular file file3 (file1 => file3):>>
+    <<diff header::Modified regular file file4 (file2 => file4):>>
     "###);
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "-s"]);
     insta::assert_snapshot!(stdout, @r###"
     M file2
     R {file1 => file3}
+    C {file2 => file4}
     "###);
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "--types"]);
     insta::assert_snapshot!(stdout, @r###"
     FF file2
     FF {file1 => file3}
+    FF {file2 => file4}
     "###);
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "--types", "glob:file[12]"]);
···
     FF file2
     "###);
 
-    let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "--git"]);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "--git", "file1"]);
     insta::assert_snapshot!(stdout, @r###"
     diff --git a/file1 b/file1
     deleted file mode 100644
···
     +++ /dev/null
     @@ -1,1 +1,0 @@
     -foo
+    "###);
+
+    let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "--git"]);
+    insta::assert_snapshot!(stdout, @r###"
     diff --git a/file2 b/file2
-    index 523a4a9de8..485b56a572 100644
+    index 94ebaf9001..1ffc51b472 100644
     --- a/file2
     +++ b/file2
-    @@ -1,2 +1,3 @@
-     foo
-    -baz qux
-    +bar
-    +baz quux
-    diff --git a/file3 b/file3
-    new file mode 100644
-    index 0000000000..257cc5642c
-    --- /dev/null
-    +++ b/file3
-    @@ -1,0 +1,1 @@
-    +foo
+    @@ -1,4 +1,3 @@
+     1
+    -2
+    +5
+     3
+    -4
+    diff --git a/file1 b/file3
+    rename from file1
+    rename to file3
+    diff --git a/file2 b/file4
+    copy from file2
+    copy to file4
     "###);
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "--git", "--context=0"]);
     insta::assert_snapshot!(stdout, @r###"
-    diff --git a/file1 b/file1
-    deleted file mode 100644
-    index 257cc5642c..0000000000
-    --- a/file1
-    +++ /dev/null
-    @@ -1,1 +1,0 @@
-    -foo
     diff --git a/file2 b/file2
-    index 523a4a9de8..485b56a572 100644
+    index 94ebaf9001..1ffc51b472 100644
     --- a/file2
     +++ b/file2
-    @@ -2,1 +2,2 @@
-    -baz qux
-    +bar
-    +baz quux
-    diff --git a/file3 b/file3
-    new file mode 100644
-    index 0000000000..257cc5642c
-    --- /dev/null
-    +++ b/file3
-    @@ -1,0 +1,1 @@
-    +foo
+    @@ -2,1 +2,1 @@
+    -2
+    +5
+    @@ -4,1 +4,0 @@
+    -4
+    diff --git a/file1 b/file3
+    rename from file1
+    rename to file3
+    diff --git a/file2 b/file4
+    copy from file2
+    copy to file4
     "###);
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "--git", "--color=debug"]);
     insta::assert_snapshot!(stdout, @r###"
-    <<diff file_header::diff --git a/file1 b/file1>>
-    <<diff file_header::deleted file mode 100644>>
-    <<diff file_header::index 257cc5642c..0000000000>>
-    <<diff file_header::--- a/file1>>
-    <<diff file_header::+++ /dev/null>>
-    <<diff hunk_header::@@ -1,1 +1,0 @@>>
-    <<diff removed::->><<diff removed token::foo>>
     <<diff file_header::diff --git a/file2 b/file2>>
-    <<diff file_header::index 523a4a9de8..485b56a572 100644>>
+    <<diff file_header::index 94ebaf9001..1ffc51b472 100644>>
     <<diff file_header::--- a/file2>>
     <<diff file_header::+++ b/file2>>
-    <<diff hunk_header::@@ -1,2 +1,3 @@>>
-    <<diff context:: foo>>
-    <<diff removed::-baz >><<diff removed token::qux>><<diff removed::>>
-    <<diff added::+>><<diff added token::bar>>
-    <<diff added::+baz >><<diff added token::quux>><<diff added::>>
-    <<diff file_header::diff --git a/file3 b/file3>>
-    <<diff file_header::new file mode 100644>>
-    <<diff file_header::index 0000000000..257cc5642c>>
-    <<diff file_header::--- /dev/null>>
-    <<diff file_header::+++ b/file3>>
-    <<diff hunk_header::@@ -1,0 +1,1 @@>>
-    <<diff added::+>><<diff added token::foo>>
+    <<diff hunk_header::@@ -1,4 +1,3 @@>>
+    <<diff context:: 1>>
+    <<diff removed::->><<diff removed token::2>><<diff removed::>>
+    <<diff added::+>><<diff added token::5>><<diff added::>>
+    <<diff context:: 3>>
+    <<diff removed::->><<diff removed token::4>>
+    <<diff file_header::diff --git a/file1 b/file3>>
+    <<diff file_header::rename from file1>>
+    <<diff file_header::rename to file3>>
+    <<diff file_header::diff --git a/file2 b/file4>>
+    <<diff file_header::copy from file2>>
+    <<diff file_header::copy to file4>>
     "###);
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "-s", "--git"]);
     insta::assert_snapshot!(stdout, @r###"
     M file2
     R {file1 => file3}
-    diff --git a/file1 b/file1
-    deleted file mode 100644
-    index 257cc5642c..0000000000
-    --- a/file1
-    +++ /dev/null
-    @@ -1,1 +1,0 @@
-    -foo
+    C {file2 => file4}
     diff --git a/file2 b/file2
-    index 523a4a9de8..485b56a572 100644
+    index 94ebaf9001..1ffc51b472 100644
     --- a/file2
     +++ b/file2
-    @@ -1,2 +1,3 @@
-     foo
-    -baz qux
-    +bar
-    +baz quux
-    diff --git a/file3 b/file3
-    new file mode 100644
-    index 0000000000..257cc5642c
-    --- /dev/null
-    +++ b/file3
-    @@ -1,0 +1,1 @@
-    +foo
+    @@ -1,4 +1,3 @@
+     1
+    -2
+    +5
+     3
+    -4
+    diff --git a/file1 b/file3
+    rename from file1
+    rename to file3
+    diff --git a/file2 b/file4
+    copy from file2
+    copy to file4
     "###);
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff", "--stat"]);
     insta::assert_snapshot!(stdout, @r###"
-    file2            | 3 ++-
+    file2            | 3 +--
     {file1 => file3} | 0
-    2 files changed, 2 insertions(+), 1 deletion(-)
+    {file2 => file4} | 0
+    3 files changed, 1 insertion(+), 2 deletions(-)
     "###);
 
     // Filter by glob pattern
···
     insta::assert_snapshot!(stdout.replace('\\', "/"), @r###"
     M repo/file2
     R repo/{file1 => file3}
+    C repo/{file2 => file4}
     "###);
     insta::assert_snapshot!(stderr.replace('\\', "/"), @r###"
     Warning: No matching entries for paths: repo/x, repo/y/z

cli/tests/test_diffedit_command.rs

···
     insta::assert_snapshot!(stdout, @r###"
     D file1
     M file2
-    A file3
+    C {file2 => file3}
     "###);
 
     // Nothing happens if the diff-editor exits with an error
···
     insta::assert_snapshot!(stdout, @r###"
     D file1
     M file2
-    A file3
+    C {file2 => file3}
     "###);
 
     // Can restore changes to individual files

cli/tests/test_git_init.rs

···
     insta::assert_snapshot!(stdout, @r###"
     @  sqpuoqvx [e-mail] 2001-02-03 08:05:07 cd1e144d
     │  (no description set)
-    │  A new-staged-file
+    │  C {some-file => new-staged-file}
     │  M some-file
-    │  A unstaged-file
+    │  C {some-file => unstaged-file}
     ○  mwrttmos [e-mail] 1970-01-01 11:02:03 my-branch HEAD@git 8d698d4a
     │  My commit message
     │  A some-file

cli/tests/test_show_command.rs

···
 
         (no description set)
 
-    diff --git a/file1 b/file1
-    deleted file mode 100644
-    index 257cc5642c..0000000000
-    --- a/file1
-    +++ /dev/null
-    @@ -1,1 +1,0 @@
-    -foo
     diff --git a/file2 b/file2
     index 523a4a9de8..485b56a572 100644
     --- a/file2
···
     -baz qux
     +bar
     +baz quux
-    diff --git a/file3 b/file3
-    new file mode 100644
-    index 0000000000..257cc5642c
-    --- /dev/null
-    +++ b/file3
-    @@ -1,0 +1,1 @@
-    +foo
+    diff --git a/file1 b/file3
+    rename from file1
+    rename to file3
     "###);
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["show", "--git", "--context=0"]);
···
 
         (no description set)
 
-    diff --git a/file1 b/file1
-    deleted file mode 100644
-    index 257cc5642c..0000000000
-    --- a/file1
-    +++ /dev/null
-    @@ -1,1 +1,0 @@
-    -foo
     diff --git a/file2 b/file2
     index 523a4a9de8..485b56a572 100644
     --- a/file2
···
     -baz qux
     +bar
     +baz quux
-    diff --git a/file3 b/file3
-    new file mode 100644
-    index 0000000000..257cc5642c
-    --- /dev/null
-    +++ b/file3
-    @@ -1,0 +1,1 @@
-    +foo
+    diff --git a/file1 b/file3
+    rename from file1
+    rename to file3
     "###);
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["show", "--git", "--color=debug"]);
···
 
     <<description placeholder::    (no description set)>>
 
-    <<diff file_header::diff --git a/file1 b/file1>>
-    <<diff file_header::deleted file mode 100644>>
-    <<diff file_header::index 257cc5642c..0000000000>>
-    <<diff file_header::--- a/file1>>
-    <<diff file_header::+++ /dev/null>>
-    <<diff hunk_header::@@ -1,1 +1,0 @@>>
-    <<diff removed::->><<diff removed token::foo>>
     <<diff file_header::diff --git a/file2 b/file2>>
     <<diff file_header::index 523a4a9de8..485b56a572 100644>>
     <<diff file_header::--- a/file2>>
···
     <<diff removed::-baz >><<diff removed token::qux>><<diff removed::>>
     <<diff added::+>><<diff added token::bar>>
     <<diff added::+baz >><<diff added token::quux>><<diff added::>>
-    <<diff file_header::diff --git a/file3 b/file3>>
-    <<diff file_header::new file mode 100644>>
-    <<diff file_header::index 0000000000..257cc5642c>>
-    <<diff file_header::--- /dev/null>>
-    <<diff file_header::+++ b/file3>>
-    <<diff hunk_header::@@ -1,0 +1,1 @@>>
-    <<diff added::+>><<diff added token::foo>>
+    <<diff file_header::diff --git a/file1 b/file3>>
+    <<diff file_header::rename from file1>>
+    <<diff file_header::rename to file3>>
     "###);
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["show", "-s", "--git"]);
···
 
     M file2
     R {file1 => file3}
-    diff --git a/file1 b/file1
-    deleted file mode 100644
-    index 257cc5642c..0000000000
-    --- a/file1
-    +++ /dev/null
-    @@ -1,1 +1,0 @@
-    -foo
     diff --git a/file2 b/file2
     index 523a4a9de8..485b56a572 100644
     --- a/file2
···
     -baz qux
     +bar
     +baz quux
-    diff --git a/file3 b/file3
-    new file mode 100644
-    index 0000000000..257cc5642c
-    --- /dev/null
-    +++ b/file3
-    @@ -1,0 +1,1 @@
-    +foo
+    diff --git a/file1 b/file3
+    rename from file1
+    rename to file3
     "###);
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["show", "--stat"]);

lib/src/git_backend.rs

···
             .changes()
             .map_err(|err| BackendError::Other(err.into()))?;
         change_platform.track_path();
+        change_platform.track_rewrites(Some(gix::diff::Rewrites {
+            copies: Some(gix::diff::rewrites::Copies {
+                source: gix::diff::rewrites::CopySource::FromSetOfModifiedFiles,
+                percentage: Some(0.5),
+            }),
+            percentage: Some(0.5),
+            limit: 1000,
+        }));
         change_platform
             .for_each_to_obtain_tree_with_cache(
                 &head_tree,