Allow restricting diff/patch output to a specific revset.

cli/src/commands/log.rs

@@ -70,6 +70,11 @@ pub(crate) struct LogArgs {
     /// Show patch
     #[arg(long, short = 'p')]
     patch: bool,
+    /// Restrict diffs to the given revsets.
+    ///
+    /// Defaults to all().
+    #[arg(long)]
+    diff_revisions: Vec<RevisionArg>,
     #[command(flatten)]
     diff_format: DiffFormatArgs,
 }
@@ -102,6 +107,14 @@ pub(crate) fn cmd_log(
         }
         expression
     };
+    let diff_revset_contains = {
+        let diff_revset_expression = if args.diff_revisions.is_empty() {
+            workspace_command.attach_revset_evaluator(RevsetExpression::all())?
+        } else {
+            workspace_command.parse_union_revsets(&args.diff_revisions)?
+        };
+        diff_revset_expression.evaluate()?.containing_fn()
+    };
 
     let repo = workspace_command.repo();
     let matcher = fileset_expression.to_matcher();
@@ -202,8 +215,10 @@ pub(crate) fn cmd_log(
                     buffer.push(b'\n');
                 }
                 if let Some(renderer) = &diff_renderer {
-                    let mut formatter = ui.new_formatter(&mut buffer);
-                    renderer.show_patch(ui, formatter.as_mut(), &commit, matcher.as_ref())?;
+                    if diff_revset_contains(commit.id()) {
+                        let mut formatter = ui.new_formatter(&mut buffer);
+                        renderer.show_patch(ui, formatter.as_mut(), &commit, matcher.as_ref())?;
+                    }
                 }
 
                 let node_symbol = format_template(ui, &Some(commit), &node_template);
@@ -243,7 +258,9 @@ pub(crate) fn cmd_log(
                 with_content_format
                     .write(formatter, |formatter| template.format(&commit, formatter))?;
                 if let Some(renderer) = &diff_renderer {
-                    renderer.show_patch(ui, formatter, &commit, matcher.as_ref())?;
+                    if diff_revset_contains(commit.id()) {
+                        renderer.show_patch(ui, formatter, &commit, matcher.as_ref())?;
+                    }
                 }
             }
         }

cli/tests/cli-reference@.md.snap

@@ -1099,6 +1099,9 @@ Spans of revisions that are not included in the graph per `--revisions` are rend
 
    For the syntax, see https://github.com/martinvonz/jj/blob/main/docs/templates.md
 * `-p`, `--patch` — Show patch
+* `--diff-revisions <DIFF_REVISIONS>` — Restrict diffs to the given revsets.
+
+   Defaults to all().
 * `-s`, `--summary` — For each path, show only whether it was modified, added, or deleted
 * `--stat` — Show a histogram of the changes
 * `--types` — For each path, show only its type before and after

cli/tests/test_log_command.rs

@@ -294,6 +294,79 @@ fn test_log_with_or_without_diff() {
     "###);
 }
 
+#[test]
+fn test_diff_revisions_restriction() {
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_ok(test_env.env_root(), &["git", "init", "repo"]);
+    let repo_path = test_env.env_root().join("repo");
+
+    std::fs::write(repo_path.join("file1"), "foo\n").unwrap();
+    test_env.jj_cmd_ok(&repo_path, &["describe", "-m", "add a file"]);
+    test_env.jj_cmd_ok(&repo_path, &["new", "-m", "a new commit"]);
+    std::fs::write(repo_path.join("file1"), "foo\nbar\n").unwrap();
+
+    // diff-revisions doesn't affect output when summary or patch is not requested.
+    let stdout = test_env.jj_cmd_success(
+        &repo_path,
+        &["log", "-T", "description", "--diff-revisions=@"],
+    );
+    insta::assert_snapshot!(stdout, @r###"
+    @  a new commit
+    ◉  add a file
+    ◉
+    "###);
+
+    // `-p` for default diff output, restrict to @
+    let stdout = test_env.jj_cmd_success(
+        &repo_path,
+        &["log", "-T", "description", "-p", "--diff-revisions=@"],
+    );
+    insta::assert_snapshot!(stdout, @r###"
+    @  a new commit
+    │  Modified regular file file1:
+    │     1    1: foo
+    │          2: bar
+    ◉  add a file
+    ◉
+    "###);
+
+    // `-p` for default diff output, `-s` for summary, restrict to @
+    let stdout = test_env.jj_cmd_success(
+        &repo_path,
+        &["log", "-T", "description", "-p", "-s", "--diff-revisions=@"],
+    );
+    insta::assert_snapshot!(stdout, @r###"
+    @  a new commit
+    │  M file1
+    │  Modified regular file file1:
+    │     1    1: foo
+    │          2: bar
+    ◉  add a file
+    ◉
+    "###);
+
+    // `-s` for summary, restrict to @-
+    let stdout = test_env.jj_cmd_success(
+        &repo_path,
+        &[
+            "log",
+            "-T",
+            "description",
+            "-p",
+            "-s",
+            "--diff-revisions=@-",
+        ],
+    );
+    insta::assert_snapshot!(stdout, @r###"
+    @  a new commit
+    ◉  add a file
+    │  A file1
+    │  Added regular file file1:
+    │          1: foo
+    ◉
+    "###);
+}
+
 #[test]
 fn test_log_null_terminate_multiline_descriptions() {
     let test_env = TestEnvironment::default();