cli: add basic support for 'jj log PATH'

In the current implementation, tree is diffed twice if both PATH and -p
are specified. If this adds significant cost, we'll need to reimplement
it without using a revset abstraction (or maybe adjust revset/graph API.)

CHANGELOG.md

@@ -138,6 +138,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * `jj log` now accepts a `--reversed` option, which will show older commits
   first.
 
+* `jj log` now accepts file paths.
+
 * `jj obslog` now accepts `-p`/`--patch` option, which will show the diff
   compared to the previous version of the change.
 

README.md

@@ -123,7 +123,7 @@ commit to any other commit using `jj move`.
 ## Status
 
 The tool is quite feature-complete, but some important features like (the
-equivalent of) `git blame` and `git log <paths>` are not yet supported. There
+equivalent of) `git blame` are not yet supported. There
 are also several performance bugs. It's also likely that workflows and setups
 different from what I personally use are not well supported. For example,
 pull-request workflows currently require too many manual steps.

src/commands.rs

@@ -1319,6 +1319,8 @@ struct LogArgs {
         default_value = "remote_branches().. | (remote_branches()..)-"
     )]
     revisions: String,
+    /// Show commits modifying the given paths
+    paths: Vec<String>,
     /// Show revisions in the opposite order (older revisions first)
     #[clap(long)]
     reversed: bool,
@@ -3114,8 +3116,12 @@ fn cmd_log(ui: &mut Ui, command: &CommandHelper, args: &LogArgs) -> Result<(), C
     let repo = workspace_command.repo();
     let workspace_id = workspace_command.workspace_id();
     let checkout_id = repo.view().get_checkout(&workspace_id);
-    let matcher = EverythingMatcher;
-    let revset = revset_expression.evaluate(repo.as_repo_ref(), Some(&workspace_id))?;
+    let matcher = matcher_from_values(ui, workspace_command.workspace_root(), &args.paths)?;
+    let mut revset = revset_expression.evaluate(repo.as_repo_ref(), Some(&workspace_id))?;
+    if !args.paths.is_empty() {
+        revset = revset::filter_by_diff(repo.as_repo_ref(), matcher.as_ref(), revset);
+    }
+
     let store = repo.store();
     let diff_format = (args.patch || args.diff_format.git || args.diff_format.summary)
         .then(|| diff_format_for(ui, &args.diff_format));
@@ -3190,7 +3196,7 @@ fn cmd_log(ui: &mut Ui, command: &CommandHelper, args: &LogArgs) -> Result<(), C
                     formatter.as_mut(),
                     &workspace_command,
                     &commit,
-                    &matcher,
+                    matcher.as_ref(),
                     diff_format,
                 )?;
             }
@@ -3216,7 +3222,7 @@ fn cmd_log(ui: &mut Ui, command: &CommandHelper, args: &LogArgs) -> Result<(), C
                     formatter,
                     &workspace_command,
                     &commit,
-                    &matcher,
+                    matcher.as_ref(),
                     diff_format,
                 )?;
             }

tests/test_log_command.rs

@@ -155,3 +155,46 @@ fn test_log_reversed() {
     second
     "###);
 }
+
+#[test]
+fn test_log_filtered_by_path() {
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
+    let repo_path = test_env.env_root().join("repo");
+
+    std::fs::write(repo_path.join("file1"), "foo\n").unwrap();
+    test_env.jj_cmd_success(&repo_path, &["describe", "-m", "first"]);
+    test_env.jj_cmd_success(&repo_path, &["new", "-m", "second"]);
+    std::fs::write(repo_path.join("file1"), "foo\nbar\n").unwrap();
+    std::fs::write(repo_path.join("file2"), "baz\n").unwrap();
+
+    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-T", "description", "file1"]);
+    insta::assert_snapshot!(stdout, @r###"
+    @ second
+    o first
+    ~ 
+    "###);
+
+    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-T", "description", "file2"]);
+    insta::assert_snapshot!(stdout, @r###"
+    @ second
+    ~ 
+    "###);
+
+    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-T", "description", "-s", "file1"]);
+    insta::assert_snapshot!(stdout, @r###"
+    @ second
+    | M file1
+    o first
+    ~ A file1
+    "###);
+
+    let stdout = test_env.jj_cmd_success(
+        &repo_path,
+        &["log", "-T", "description", "-s", "file2", "--no-graph"],
+    );
+    insta::assert_snapshot!(stdout, @r###"
+    second
+    A file2
+    "###);
+}