git: add a hidden submodule subcommand

Add the `submodule` subcommand, which will remain hidden while we are
polishing up the submodules feature. Also, add a debugging-only
sub-subcommand `print-gitmodules` that tests our .gitmodules parser with
the .gitmodules in the working copy.

src/cli_util.rs

@@ -31,7 +31,7 @@ use indexmap::IndexSet;
 use itertools::Itertools;
 use jujutsu_lib::backend::{BackendError, ChangeId, CommitId, ObjectId, TreeId};
 use jujutsu_lib::commit::Commit;
-use jujutsu_lib::git::{GitExportError, GitImportError};
+use jujutsu_lib::git::{GitConfigParseError, GitExportError, GitImportError};
 use jujutsu_lib::git_backend::GitBackend;
 use jujutsu_lib::gitignore::GitIgnoreFile;
 use jujutsu_lib::hex_util::to_reverse_hex;
@@ -325,6 +325,12 @@ impl From<clap::Error> for CommandError {
     }
 }
 
+impl From<GitConfigParseError> for CommandError {
+    fn from(err: GitConfigParseError) -> Self {
+        CommandError::InternalError(format!("Failed to parse Git config: {err} "))
+    }
+}
+
 /// Handle to initialize or change tracing subscription.
 #[derive(Clone, Debug)]
 pub struct TracingSubscription {

src/commands/git.rs

@@ -8,12 +8,13 @@ use std::time::Instant;
 
 use clap::{ArgGroup, Subcommand};
 use itertools::Itertools;
-use jujutsu_lib::backend::ObjectId;
-use jujutsu_lib::git::{self, GitFetchError, GitPushError, GitRefUpdate};
+use jujutsu_lib::backend::{ObjectId, TreeValue};
+use jujutsu_lib::git::{self, parse_gitmodules, GitFetchError, GitPushError, GitRefUpdate};
 use jujutsu_lib::git_backend::GitBackend;
 use jujutsu_lib::op_store::{BranchTarget, RefTarget};
 use jujutsu_lib::refs::{classify_branch_push_action, BranchPushAction, BranchPushUpdate};
 use jujutsu_lib::repo::Repo;
+use jujutsu_lib::repo_path::RepoPath;
 use jujutsu_lib::revset::{self, RevsetIteratorExt as _};
 use jujutsu_lib::settings::{ConfigResultExt as _, UserSettings};
 use jujutsu_lib::store::Store;
@@ -43,6 +44,8 @@ pub enum GitCommands {
     Push(GitPushArgs),
     Import(GitImportArgs),
     Export(GitExportArgs),
+    #[command(subcommand, hide = true)]
+    Submodule(GitSubmoduleCommands),
 }
 
 /// Manage Git remotes
@@ -155,6 +158,23 @@ pub struct GitImportArgs {}
 #[derive(clap::Args, Clone, Debug)]
 pub struct GitExportArgs {}
 
+/// FOR INTERNAL USE ONLY Interact with git submodules
+#[derive(Subcommand, Clone, Debug)]
+pub enum GitSubmoduleCommands {
+    /// Print the relevant contents from .gitmodules. For debugging purposes
+    /// only.
+    PrintGitmodules(GitSubmodulePrintGitmodulesArgs),
+}
+
+/// Print debugging info about Git submodules
+#[derive(clap::Args, Clone, Debug)]
+#[command(hide = true)]
+pub struct GitSubmodulePrintGitmodulesArgs {
+    /// Read .gitmodules from the given revision.
+    #[arg(long, short = 'r', default_value = "@")]
+    revisions: RevisionArg,
+}
+
 fn get_git_repo(store: &Store) -> Result<git2::Repository, CommandError> {
     match store.backend_impl().downcast_ref::<GitBackend>() {
         None => Err(user_error("The repo is not backed by a git repo")),
@@ -1016,6 +1036,37 @@ fn cmd_git_export(
     Ok(())
 }
 
+fn cmd_git_submodule_print_gitmodules(
+    ui: &mut Ui,
+    command: &CommandHelper,
+    args: &GitSubmodulePrintGitmodulesArgs,
+) -> Result<(), CommandError> {
+    let workspace_command = command.workspace_helper(ui)?;
+    let repo = workspace_command.repo();
+    let commit = workspace_command.resolve_single_rev(&args.revisions)?;
+    let gitmodules_path = RepoPath::from_internal_string(".gitmodules");
+    let mut gitmodules_file = match commit.tree().path_value(&gitmodules_path) {
+        None => {
+            writeln!(ui, "No submodules!")?;
+            return Ok(());
+        }
+        Some(TreeValue::File { id, .. }) => repo.store().read_file(&gitmodules_path, &id)?,
+        _ => {
+            return Err(user_error(".gitmodules is not a file."));
+        }
+    };
+
+    let submodules = parse_gitmodules(&mut gitmodules_file)?;
+    for (name, submodule) in submodules {
+        writeln!(
+            ui,
+            "name:{}\nurl:{}\npath:{}\n\n",
+            name, submodule.url, submodule.path
+        )?;
+    }
+    Ok(())
+}
+
 pub fn cmd_git(
     ui: &mut Ui,
     command: &CommandHelper,
@@ -1039,5 +1090,8 @@ pub fn cmd_git(
         GitCommands::Push(command_matches) => cmd_git_push(ui, command, command_matches),
         GitCommands::Import(command_matches) => cmd_git_import(ui, command, command_matches),
         GitCommands::Export(command_matches) => cmd_git_export(ui, command, command_matches),
+        GitCommands::Submodule(GitSubmoduleCommands::PrintGitmodules(command_matches)) => {
+            cmd_git_submodule_print_gitmodules(ui, command, command_matches)
+        }
     }
 }

tests/test_git_submodule.rs

@@ -0,0 +1,65 @@
+// Copyright 2020 The Jujutsu Authors
+//
+// 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_gitsubmodule_print_gitmodules() {
+    let test_env = TestEnvironment::default();
+    let workspace_root = test_env.env_root().join("repo");
+    git2::Repository::init(&workspace_root).unwrap();
+    test_env.jj_cmd_success(&workspace_root, &["init", "--git-repo", "."]);
+
+    std::fs::write(
+        workspace_root.join(".gitmodules"),
+        "
+[submodule \"old\"]
+	path = old
+	url = https://github.com/old/old.git
+",
+    )
+    .unwrap();
+
+    test_env.jj_cmd_success(&workspace_root, &["new"]);
+
+    std::fs::write(
+        workspace_root.join(".gitmodules"),
+        "
+[submodule \"new\"]
+	path = new
+	url = https://github.com/new/new.git
+",
+    )
+    .unwrap();
+
+    let stdout = test_env.jj_cmd_success(
+        &workspace_root,
+        &["git", "submodule", "print-gitmodules", "-r", "@-"],
+    );
+    insta::assert_snapshot!(stdout, @r###"
+	name:old
+	url:https://github.com/old/old.git
+	path:old
+    "###);
+
+    let stdout =
+        test_env.jj_cmd_success(&workspace_root, &["git", "submodule", "print-gitmodules"]);
+    insta::assert_snapshot!(stdout, @r###"
+	name:new
+	url:https://github.com/new/new.git
+	path:new
+    "###);
+}