cli: rename print to cat

`jj cat` better matches `hg cat` and, of course, `cat`. I apparently
called it `jj print` when I added it in 7a013a59ae because I haven't
found `hg cat` useful for actually concatenating files. That's still
true, and I don't know if we will ever bother to teach `jj cat` to
actually concatenate files, but I think the familiarity of `cat` is
more important.

For reference, Git calls it `git show <rev>:<file>`.

I kept `print` as an alias and added a test for it. I also documented
the test better.

By the way, I've considered adding a command for writing from stdin
directly to a specific commit. If we ever do, it might make sense to
call that command `write` (e.g. `echo foo | jj write -r @-
README.md`). Then it would make sense to add `read` as an alias to
`cat`. I'm not sure that's a good idea, but let's leave that for later
anyway.

CHANGELOG.md

@@ -70,6 +70,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * `jj log` now highlights the shortest unique prefix of every commit and change id
   with brackets. To disable, set the new `ui.unique-prefixes` option to `none`
 
+* `jj print` was renamed to `jj cat`. `jj print` remains as an alias.
+
 ### Fixed bugs
 
 * When sharing the working copy with a Git repo, we used to forget to export

src/commands.rs

@@ -77,7 +77,8 @@ enum Commands {
     Checkout(CheckoutArgs),
     Untrack(UntrackArgs),
     Files(FilesArgs),
-    Print(PrintArgs),
+    #[command(alias = "print")]
+    Cat(CatArgs),
     Diff(DiffArgs),
     Show(ShowArgs),
     Status(StatusArgs),
@@ -229,7 +230,7 @@ struct FilesArgs {
 
 /// Print contents of a file in a revision
 #[derive(clap::Args, Clone, Debug)]
-struct PrintArgs {
+struct CatArgs {
     /// The revision to get the file contents from
     #[arg(long, short, default_value = "@")]
     revision: RevisionArg,
@@ -1382,7 +1383,7 @@ fn cmd_files(ui: &mut Ui, command: &CommandHelper, args: &FilesArgs) -> Result<(
     Ok(())
 }
 
-fn cmd_print(ui: &mut Ui, command: &CommandHelper, args: &PrintArgs) -> Result<(), CommandError> {
+fn cmd_cat(ui: &mut Ui, command: &CommandHelper, args: &CatArgs) -> Result<(), CommandError> {
     let workspace_command = command.workspace_helper(ui)?;
     let commit = workspace_command.resolve_single_rev(&args.revision)?;
     let path = workspace_command.parse_file_path(&args.path)?;
@@ -4596,7 +4597,7 @@ pub fn run_command(
         Commands::Checkout(sub_args) => cmd_checkout(ui, command_helper, sub_args),
         Commands::Untrack(sub_args) => cmd_untrack(ui, command_helper, sub_args),
         Commands::Files(sub_args) => cmd_files(ui, command_helper, sub_args),
-        Commands::Print(sub_args) => cmd_print(ui, command_helper, sub_args),
+        Commands::Cat(sub_args) => cmd_cat(ui, command_helper, sub_args),
         Commands::Diff(sub_args) => cmd_diff(ui, command_helper, sub_args),
         Commands::Show(sub_args) => cmd_show(ui, command_helper, sub_args),
         Commands::Status(sub_args) => cmd_status(ui, command_helper, sub_args),

tests/test_cat_command.rs

@@ -17,7 +17,7 @@ use crate::common::TestEnvironment;
 pub mod common;
 
 #[test]
-fn test_print() {
+fn test_cat() {
     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");
@@ -28,28 +28,43 @@ fn test_print() {
     std::fs::create_dir(repo_path.join("dir")).unwrap();
     std::fs::write(repo_path.join("dir").join("file2"), "c\n").unwrap();
 
-    let stdout = test_env.jj_cmd_success(&repo_path, &["print", "file1", "-r", "@-"]);
+    // Can print the contents of a file in a commit
+    let stdout = test_env.jj_cmd_success(&repo_path, &["cat", "file1", "-r", "@-"]);
     insta::assert_snapshot!(stdout, @r###"
     a
     "###);
+
+    // Defaults to printing the working-copy version
+    let stdout = test_env.jj_cmd_success(&repo_path, &["cat", "file1"]);
+    insta::assert_snapshot!(stdout, @r###"
+    b
+    "###);
+
+    // `print` is an alias for `cat`
     let stdout = test_env.jj_cmd_success(&repo_path, &["print", "file1"]);
     insta::assert_snapshot!(stdout, @r###"
     b
     "###);
+
+    // Can print a file in a subdirectory
     let subdir_file = if cfg!(unix) {
         "dir/file2"
     } else {
         "dir\\file2"
     };
-    let stdout = test_env.jj_cmd_success(&repo_path, &["print", subdir_file]);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["cat", subdir_file]);
     insta::assert_snapshot!(stdout, @r###"
     c
     "###);
-    let stderr = test_env.jj_cmd_failure(&repo_path, &["print", "nonexistent"]);
+
+    // Error if the path doesn't exist
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["cat", "nonexistent"]);
     insta::assert_snapshot!(stderr, @r###"
     Error: No such path
     "###);
-    let stderr = test_env.jj_cmd_failure(&repo_path, &["print", "dir"]);
+
+    // Error if the path is not a file
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["cat", "dir"]);
     insta::assert_snapshot!(stderr, @r###"
     Error: Path exists but is not a file
     "###);
@@ -58,7 +73,7 @@ fn test_print() {
     test_env.jj_cmd_success(&repo_path, &["new"]);
     std::fs::write(repo_path.join("file1"), "c\n").unwrap();
     test_env.jj_cmd_success(&repo_path, &["rebase", "-r", "@", "-d", "@--"]);
-    let stdout = test_env.jj_cmd_success(&repo_path, &["print", "file1"]);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["cat", "file1"]);
     insta::assert_snapshot!(stdout, @r###"
     <<<<<<<
     %%%%%%%