ok/jj
1
0
Fork 0
forked from mirrors/jj
Code Pull requests Activity

git: make change id the reverse bits of commit id

Browse source 
The fact that the default change id in git repos is currently a prefix
of the commit id makes it impossible to use for resolving a prefix of
the change id to commits. This patch addresses that by reversing the
bits of the change id (relative to the commit id). The next patch will
make it so a change id (or a prefix thereof) is a valid revset.
This commit is contained in:
Martin von Zweigbergk 2021-05-29 23:52:50 -07:00
parent c7f701fddb
commit ca1df00e05
1 changed files with 19 additions and 6 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

25
lib/src/git_store.rs
View file

@ -318,7 +318,19 @@ impl Store for GitStore {
let locked_repo = self.repo.lock().unwrap();
let git_commit_id = Oid::from_bytes(id.0.as_slice())?;
let commit = locked_repo.find_commit(git_commit_id)?;
let change_id = ChangeId(id.0.clone().as_slice()[0..16].to_vec());
// We reverse the bits of the commit id to create the change id. We don't want
// to use the first bytes unmodified because then it would be ambiguous
// if a given hash prefix refers to the commit id or the change id. It
// would have been enough to pick the last 16 bytes instead of the
// leading 16 bytes to address that. We also reverse the bits to make it less
// likely that users depend on any relationship between the two ids.
let change_id = ChangeId(
id.0.clone().as_slice()[4..20]
.iter()
.rev()
.map(|b| b.reverse_bits())
.collect(),
);
let parents: Vec<_> = commit
.parent_ids()
.map(|oid| CommitId(oid.as_bytes().to_vec()))
@ -535,14 +547,15 @@ mod tests {
&[],
)
.unwrap();
let commit_id = CommitId(git_commit_id.as_bytes().to_vec());
let commit_id = CommitId::from_hex("efdcea5ca4b3658149f899ca7feee6876d077263");
// The change id is the leading reverse bits of the commit id
let change_id = ChangeId::from_hex("c64ee0b6e16777fe53991f9281a6cd25");
// Check that the git commit above got the hash we expect
assert_eq!(git_commit_id.as_bytes(), &commit_id.0);
let store = GitStore::load(git_repo_path);
let commit = store.read_commit(&commit_id).unwrap();
assert_eq!(
&commit.change_id,
&ChangeId(commit_id.0.as_slice()[0..16].to_vec())
);
assert_eq!(&commit.change_id, &change_id);
assert_eq!(commit.parents, vec![]);
assert_eq!(commit.predecessors, vec![]);
assert_eq!(commit.root_tree.0.as_slice(), root_tree_id.as_bytes());