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git: add hack to unset Git HEAD by using placeholder ref

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As we can set HEAD to an arbitrary ref by using .reference_symbolic(), we don't
have to manage a ref that can also be valid as a branch name.

Fixes #1495
This commit is contained in:
Yuya Nishihara 2023-10-03 19:45:03 +09:00
parent 048f993a17
commit a302090de9
3 changed files with 212 additions and 0 deletions
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132
cli/tests/test_git_colocated.rs
View file

@ -95,6 +95,138 @@ fn test_git_colocated() {
);
}
#[test]
fn test_git_colocated_unborn_branch() {
let test_env = TestEnvironment::default();
let workspace_root = test_env.env_root().join("repo");
let git_repo = git2::Repository::init(&workspace_root).unwrap();
let add_file_to_index = |name: &str, data: &str| {
std::fs::write(workspace_root.join(name), data).unwrap();
let mut index = git_repo.index().unwrap();
index.add_path(Path::new(name)).unwrap();
index.write().unwrap();
};
let checkout_index = || {
let mut index = git_repo.index().unwrap();
index.read(true).unwrap(); // discard in-memory cache
git_repo.checkout_index(Some(&mut index), None).unwrap();
};
// Initially, HEAD isn't set.
test_env.jj_cmd_success(&workspace_root, &["init", "--git-repo", "."]);
assert!(git_repo.head().is_err());
assert_eq!(
git_repo.find_reference("HEAD").unwrap().symbolic_target(),
Some("refs/heads/master")
);
insta::assert_snapshot!(get_log_output(&test_env, &workspace_root), @r###"
@ 230dd059e1b059aefc0da06a2e5a7dbf22362f22
◉ 0000000000000000000000000000000000000000
"###);
// Stage some change, and check out root. This shouldn't clobber the HEAD.
add_file_to_index("file0", "");
insta::assert_snapshot!(
test_env.jj_cmd_success(&workspace_root, &["checkout", "root()"]), @r###"
Working copy now at: kkmpptxz fcdbbd73 (empty) (no description set)
Parent commit : zzzzzzzz 00000000 (empty) (no description set)
Added 0 files, modified 0 files, removed 1 files
"###);
assert!(git_repo.head().is_err());
assert_eq!(
git_repo.find_reference("HEAD").unwrap().symbolic_target(),
Some("refs/heads/master")
);
insta::assert_snapshot!(get_log_output(&test_env, &workspace_root), @r###"
@ fcdbbd731496cae17161cd6be9b6cf1f759655a8
│ ◉ 1de814dbef9641cc6c5c80d2689b80778edcce09
├─╯
◉ 0000000000000000000000000000000000000000
"###);
// Staged change shouldn't persist.
checkout_index();
insta::assert_snapshot!(test_env.jj_cmd_success(&workspace_root, &["status"]), @r###"
The working copy is clean
Working copy : kkmpptxz fcdbbd73 (empty) (no description set)
Parent commit: zzzzzzzz 00000000 (empty) (no description set)
"###);
// Stage some change, and create new HEAD. This shouldn't move the default
// branch.
add_file_to_index("file1", "");
insta::assert_snapshot!(test_env.jj_cmd_success(&workspace_root, &["new"]), @r###"
Working copy now at: royxmykx 76c60bf0 (empty) (no description set)
Parent commit : kkmpptxz f8d5bc77 (no description set)
"###);
assert!(git_repo.head().unwrap().symbolic_target().is_none());
insta::assert_snapshot!(
git_repo.head().unwrap().peel_to_commit().unwrap().id().to_string(),
@"f8d5bc772d1147351fd6e8cea52a4f935d3b31e7"
);
insta::assert_snapshot!(get_log_output(&test_env, &workspace_root), @r###"
@ 76c60bf0a66dcbe74d74d58c23848d96f9e86e84
◉ f8d5bc772d1147351fd6e8cea52a4f935d3b31e7 HEAD@git
│ ◉ 1de814dbef9641cc6c5c80d2689b80778edcce09
├─╯
◉ 0000000000000000000000000000000000000000
"###);
// Staged change shouldn't persist.
checkout_index();
insta::assert_snapshot!(test_env.jj_cmd_success(&workspace_root, &["status"]), @r###"
The working copy is clean
Working copy : royxmykx 76c60bf0 (empty) (no description set)
Parent commit: kkmpptxz f8d5bc77 (no description set)
"###);
// Assign the default branch. The branch is no longer "unborn".
test_env.jj_cmd_success(&workspace_root, &["branch", "set", "-r@-", "master"]);
// Stage some change, and check out root again. This should unset the HEAD.
// https://github.com/martinvonz/jj/issues/1495
add_file_to_index("file2", "");
insta::assert_snapshot!(
test_env.jj_cmd_success(&workspace_root, &["checkout", "root()"]), @r###"
Working copy now at: znkkpsqq 10dd328b (empty) (no description set)
Parent commit : zzzzzzzz 00000000 (empty) (no description set)
Added 0 files, modified 0 files, removed 2 files
"###);
assert!(git_repo.head().is_err());
insta::assert_snapshot!(get_log_output(&test_env, &workspace_root), @r###"
@ 10dd328bb906e15890e55047740eab2812a3b2f7
│ ◉ 2c576a57d2e6e8494616629cfdbb8fe5e3fea73b
│ ◉ f8d5bc772d1147351fd6e8cea52a4f935d3b31e7 master
├─╯
│ ◉ 1de814dbef9641cc6c5c80d2689b80778edcce09
├─╯
◉ 0000000000000000000000000000000000000000
"###);
// Staged change shouldn't persist.
checkout_index();
insta::assert_snapshot!(test_env.jj_cmd_success(&workspace_root, &["status"]), @r###"
The working copy is clean
Working copy : znkkpsqq 10dd328b (empty) (no description set)
Parent commit: zzzzzzzz 00000000 (empty) (no description set)
"###);
// New snapshot and commit can be created after the HEAD got unset.
std::fs::write(workspace_root.join("file3"), "").unwrap();
insta::assert_snapshot!(test_env.jj_cmd_success(&workspace_root, &["new"]), @r###"
Working copy now at: wqnwkozp cab23370 (empty) (no description set)
Parent commit : znkkpsqq 8f5b2638 (no description set)
"###);
insta::assert_snapshot!(get_log_output(&test_env, &workspace_root), @r###"
@ cab233704a5c0b21bde070943055f22142fb2043
◉ 8f5b263819457712a2937428b9c58a2a84afbb1c HEAD@git
│ ◉ 2c576a57d2e6e8494616629cfdbb8fe5e3fea73b
│ ◉ f8d5bc772d1147351fd6e8cea52a4f935d3b31e7 master
├─╯
│ ◉ 1de814dbef9641cc6c5c80d2689b80778edcce09
├─╯
◉ 0000000000000000000000000000000000000000
"###);
}
#[test]
fn test_git_colocated_export_branches_on_snapshot() {
// Checks that we export branches that were changed only because the working

21
lib/src/git.rs
View file

@ -36,6 +36,8 @@ use crate::view::{RefName, View};
/// Reserved remote name for the backing Git repo.
pub const REMOTE_NAME_FOR_LOCAL_GIT_REPO: &str = "git";
/// Ref name used as a placeholder to unset HEAD without a commit.
const UNBORN_ROOT_REF_NAME: &str = "refs/jj/root";
#[derive(Error, Debug)]
pub enum GitImportError {
@ -690,6 +692,25 @@ pub fn reset_head(
git_repo.set_head_detached(new_git_commit_id)?;
git_repo.reset(new_git_commit.as_object(), git2::ResetType::Mixed, None)?;
mut_repo.set_git_head_target(RefTarget::normal(first_parent_id.clone()));
} else {
// Can't detach HEAD without a commit. Use placeholder ref to nullify the HEAD.
// We can't set_head() an arbitrary unborn ref, so use reference_symbolic()
// instead. Git CLI appears to deal with that. It would be nice if Git CLI
// couldn't create a commit without setting a valid branch name.
if mut_repo.git_head().is_present() {
match git_repo.find_reference(UNBORN_ROOT_REF_NAME) {
Ok(mut git_repo_ref) => git_repo_ref.delete()?,
Err(err) if err.code() == git2::ErrorCode::NotFound => {}
Err(err) => return Err(err),
}
git_repo.reference_symbolic("HEAD", UNBORN_ROOT_REF_NAME, true, "unset HEAD by jj")?;
}
// git_reset() of libgit2 requires a commit object. Do that manually.
let mut index = git_repo.index()?;
index.clear()?; // or read empty tree
index.write()?;
git_repo.cleanup_state()?;
mut_repo.set_git_head_target(RefTarget::absent());
}
Ok(())
}

59
lib/tests/test_git.rs
View file

@ -35,6 +35,7 @@ use jj_lib::op_store::{BranchTarget, RefTarget};
use jj_lib::repo::{MutableRepo, ReadonlyRepo, Repo};
use jj_lib::settings::{GitSettings, UserSettings};
use jj_lib::view::RefName;
use jj_lib::workspace::Workspace;
use maplit::{btreemap, hashset};
use tempfile::TempDir;
use testutils::{
@ -1572,6 +1573,64 @@ fn test_export_reexport_transitions() {
);
}
#[test]
fn test_reset_head_to_root() {
// Create colocated workspace
let settings = testutils::user_settings();
let temp_dir = testutils::new_temp_dir();
let workspace_root = temp_dir.path().join("repo");
let git_repo = git2::Repository::init(&workspace_root).unwrap();
let (_workspace, repo) =
Workspace::init_external_git(&settings, &workspace_root, &workspace_root.join(".git"))
.unwrap();
let mut tx = repo.start_transaction(&settings, "test");
let mut_repo = tx.mut_repo();
let root_commit_id = repo.store().root_commit_id();
let tree_id = repo.store().empty_merged_tree_id();
let commit1 = mut_repo
.new_commit(&settings, vec![root_commit_id.clone()], tree_id.clone())
.write()
.unwrap();
let commit2 = mut_repo
.new_commit(&settings, vec![commit1.id().clone()], tree_id.clone())
.write()
.unwrap();
// Set Git HEAD to commit2's parent (i.e. commit1)
git::reset_head(tx.mut_repo(), &git_repo, &commit2).unwrap();
assert!(git_repo.head().is_ok());
assert_eq!(
tx.mut_repo().git_head(),
RefTarget::normal(commit1.id().clone())
);
// Set Git HEAD back to root
git::reset_head(tx.mut_repo(), &git_repo, &commit1).unwrap();
assert!(git_repo.head().is_err());
assert!(tx.mut_repo().git_head().is_absent());
// Move placeholder ref as if new commit were created by git
git_repo
.reference("refs/jj/root", git_id(&commit1), false, "")
.unwrap();
git::reset_head(tx.mut_repo(), &git_repo, &commit2).unwrap();
assert!(git_repo.head().is_ok());
assert_eq!(
tx.mut_repo().git_head(),
RefTarget::normal(commit1.id().clone())
);
assert!(git_repo.find_reference("refs/jj/root").is_ok());
// Set Git HEAD back to root
git::reset_head(tx.mut_repo(), &git_repo, &commit1).unwrap();
assert!(git_repo.head().is_err());
assert!(tx.mut_repo().git_head().is_absent());
// The placeholder ref should be deleted
assert!(git_repo.find_reference("refs/jj/root").is_err());
}
#[test]
fn test_init() {
let settings = testutils::user_settings();