tests: add test for jj git clone

We didn't seem to have any. I included a test for #399.

The tests also showed how the debug formatting (`{:?}`) results in
escaped (e.g.) backslashes on Windows, which is not what we want, so I
also fixed that.

src/commands.rs

@@ -4993,7 +4993,7 @@ fn cmd_git_clone(
 
     let (workspace, repo) = Workspace::init_internal_git(ui.settings(), wc_path.clone())?;
     let git_repo = get_git_repo(repo.store())?;
-    writeln!(ui, "Fetching into new repo in {:?}", wc_path)?;
+    writeln!(ui, r#"Fetching into new repo in "{}""#, wc_path.display())?;
     let mut workspace_command = command.for_loaded_repo(ui, workspace, repo)?;
     let remote_name = "origin";
     git_repo.remote(remote_name, source).unwrap();

tests/test_git_clone.rs

@@ -0,0 +1,84 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use crate::common::TestEnvironment;
+
+pub mod common;
+
+#[test]
+fn test_git_clone() {
+    let test_env = TestEnvironment::default();
+    let git_repo_path = test_env.env_root().join("source");
+    let git_repo = git2::Repository::init(&git_repo_path).unwrap();
+
+    // Clone an empty repo
+    let stdout = test_env.jj_cmd_success(test_env.env_root(), &["git", "clone", "source", "empty"]);
+    insta::assert_snapshot!(stdout.replace(test_env.env_root().join("empty").to_str().unwrap(), "<dest>"), @r###"
+    Fetching into new repo in "<dest>"
+    Nothing changed.
+    "###);
+
+    // Clone a non-empty repo
+    let signature =
+        git2::Signature::new("Some One", "some.one@example.com", &git2::Time::new(0, 0)).unwrap();
+    let mut tree_builder = git_repo.treebuilder(None).unwrap();
+    let file_oid = git_repo.blob(b"content").unwrap();
+    tree_builder
+        .insert("file", file_oid, git2::FileMode::Blob.into())
+        .unwrap();
+    let tree_oid = tree_builder.write().unwrap();
+    let tree = git_repo.find_tree(tree_oid).unwrap();
+    git_repo
+        .commit(
+            Some("refs/heads/main"),
+            &signature,
+            &signature,
+            "message",
+            &tree,
+            &[],
+        )
+        .unwrap();
+    git_repo.set_head("refs/heads/main").unwrap();
+    let stdout = test_env.jj_cmd_success(test_env.env_root(), &["git", "clone", "source", "clone"]);
+    insta::assert_snapshot!(stdout.replace(test_env.env_root().join("clone").to_str().unwrap(), "<dest>"), @r###"
+    Fetching into new repo in "<dest>"
+    Working copy now at: 1f0b881a057d (no description set)
+    Added 1 files, modified 0 files, removed 0 files
+    "###);
+    assert!(test_env.env_root().join("clone").join("file").exists());
+
+    // Try cloning into an existing workspace
+    let stderr = test_env.jj_cmd_failure(test_env.env_root(), &["git", "clone", "source", "clone"]);
+    insta::assert_snapshot!(stderr.replace(test_env.env_root().join("clone").to_str().unwrap(), "<dest>"), @r###"
+    Error: The target repo already exists
+    "###);
+
+    // Try cloning into an existing file
+    std::fs::write(test_env.env_root().join("file"), "contents").unwrap();
+    // TODO: This shouldn't crash (i.e. not exit code 101)
+    test_env
+        .jj_cmd(test_env.env_root(), &["git", "clone", "source", "file"])
+        .assert()
+        .code(101);
+
+    // Try cloning into non-empty, non-workspace directory
+    std::fs::remove_dir_all(test_env.env_root().join("clone").join(".jj")).unwrap();
+    // TODO: This should fail (https://github.com/martinvonz/jj/issues/399)
+    let stdout = test_env.jj_cmd_success(test_env.env_root(), &["git", "clone", "source", "clone"]);
+    insta::assert_snapshot!(stdout.replace(test_env.env_root().join("clone").to_str().unwrap(), "<dest>"), @r###"
+    Fetching into new repo in "<dest>"
+    Working copy now at: b56015e38065 (no description set)
+    Added 1 files, modified 0 files, removed 0 files
+    "###);
+}