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Merged
Pajn merged 1 commit into from
May 22, 2026
Merged

Restack fixes #48

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242 changes: 205 additions & 37 deletions src/stack.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -716,6 +716,7 @@ pub fn collect_merged_local_branches(
pub struct FloatingTargetContext {
candidates: Vec<FloatingTargetCandidate>,
candidate_ids: HashSet<Oid>,
candidate_positions: HashMap<Oid, usize>,
patch_ids: HashSet<String>,
reflog_ids: HashSet<Oid>,
}
Expand All @@ -729,6 +730,12 @@ struct FloatingTargetCandidate {
parent_id: Option<Oid>,
}

#[derive(Clone, Copy)]
struct FloatingBaseMatch {
branch_id: Oid,
target_index: usize,
}

fn floating_patch_id_boundary(
repo: &Repository,
target_id: Oid,
Expand Down Expand Up @@ -769,7 +776,7 @@ pub fn build_floating_target_context(
history_limit: usize,
patch_id_cache: &mut HashMap<Oid, Option<String>>,
) -> Result<FloatingTargetContext> {
let mut candidates = Vec::new();
let mut all_candidates = Vec::new();
let mut commit_ids = Vec::new();
let mut current = Some(target_commit.id());
let mut remaining = history_limit;
Expand All @@ -779,7 +786,7 @@ pub fn build_floating_target_context(
break;
}
let commit = repo.find_commit(commit_id)?;
candidates.push(FloatingTargetCandidate {
all_candidates.push(FloatingTargetCandidate {
id: commit_id,
tree_id: commit.tree_id(),
summary: commit.summary().unwrap_or("").trim().to_string(),
Expand All @@ -802,6 +809,13 @@ pub fn build_floating_target_context(
}

let patch_id_boundary = floating_patch_id_boundary(repo, target_commit.id(), target_branch)?;
let private_len = match patch_id_boundary {
Some(boundary) => commit_ids
.iter()
.position(|oid| *oid == boundary)
.unwrap_or(commit_ids.len()),
None => commit_ids.len(),
};
let patch_commit_ids: Vec<Oid> = match patch_id_boundary {
Some(boundary) => commit_ids
.iter()
Expand All @@ -819,11 +833,20 @@ pub fn build_floating_target_context(
.iter()
.filter_map(|oid| patch_id_cache.get(oid).and_then(|v| v.as_ref()).cloned())
.collect();
let candidates: Vec<FloatingTargetCandidate> =
all_candidates.into_iter().take(private_len).collect();
let candidate_ids = candidates.iter().map(|candidate| candidate.id).collect();
let candidate_positions = candidates
.iter()
.enumerate()
.map(|(index, candidate)| (candidate.id, index))
.collect();
let reflog_ids = read_branch_reflog_ids(repo, target_branch);

Ok(FloatingTargetContext {
candidate_ids: commit_ids.into_iter().collect(),
candidates,
candidate_ids,
candidate_positions,
patch_ids,
reflog_ids,
})
Expand All @@ -836,13 +859,20 @@ pub fn find_floating_base(
history_limit: usize,
patch_id_cache: &mut HashMap<Oid, Option<String>>,
) -> Result<Option<Oid>> {
let target_id = target
.candidates
.first()
.map(|candidate| candidate.id)
.ok_or_else(|| {
anyhow!("Expected at least one target commit for floating-base detection.")
})?;
find_floating_match(repo, branch_tip, target, history_limit, patch_id_cache)
.map(|found| found.map(|matching| matching.branch_id))
}

fn find_floating_match(
repo: &Repository,
branch_tip: Oid,
target: &FloatingTargetContext,
history_limit: usize,
patch_id_cache: &mut HashMap<Oid, Option<String>>,
) -> Result<Option<FloatingBaseMatch>> {
let Some(target_id) = target.candidates.first().map(|candidate| candidate.id) else {
return Ok(None);
};

// If the branch is already on top of, already part of, or already integrated
// into the target branch, it is not a floating child that needs restacking.
Expand Down Expand Up @@ -875,38 +905,54 @@ pub fn find_floating_base(
remaining -= 1;
}

if target.candidate_ids.contains(&oid) {
if let Some(&target_index) = target.candidate_positions.get(&oid) {
if oid != branch_tip {
return Ok(Some(oid));
let matching = FloatingBaseMatch {
branch_id: oid,
target_index,
};
if validate_floating_match(repo, branch_tip, matching, target, patch_id_cache)? {
return Ok(Some(matching));
}
}
continue;
}

// Match by tree-hash against rewritten target commits, but only if the
// surrounding parent commit also lines up with the rewritten lineage.
let mut has_tree_match = false;
for candidate in &target.candidates {
for (target_index, candidate) in target.candidates.iter().enumerate() {
if candidate.tree_id != commit.tree_id() {
continue;
}
if floating_parent_matches_candidate(
if !floating_parent_matches_candidate(
repo,
parent_id,
candidate.parent_id,
patch_id_cache,
)? {
has_tree_match = true;
break;
continue;
}
if oid != branch_tip {
let matching = FloatingBaseMatch {
branch_id: oid,
target_index,
};
if validate_floating_match(repo, branch_tip, matching, target, patch_id_cache)? {
return Ok(Some(matching));
}
}
}
if has_tree_match && oid != branch_tip {
return Ok(Some(oid));
}

// Metadata matches narrow the patch-id fallback, but are not sufficient on their own.
if metadata_matches_target_candidate(&commit, oid, target)? {
if oid != branch_tip {
return Ok(Some(oid));
if let Some(target_index) = metadata_matches_target_candidate(&commit, oid, target)?
&& oid != branch_tip
{
let matching = FloatingBaseMatch {
branch_id: oid,
target_index,
};
if validate_floating_match(repo, branch_tip, matching, target, patch_id_cache)? {
return Ok(Some(matching));
}
continue;
}
Expand Down Expand Up @@ -968,7 +1014,14 @@ pub fn find_floating_base(

if !old_parent_ancestor_of_any_candidate {
// OLD.parent is NOT an ancestor of any candidate - it's orphaned, rebase fork
return Ok(Some(oid));
let matching = FloatingBaseMatch {
branch_id: oid,
target_index: 0,
};
if validate_floating_match(repo, branch_tip, matching, target, patch_id_cache)?
{
return Ok(Some(matching));
}
}
}
}
Expand All @@ -990,8 +1043,7 @@ pub fn find_floating_base(

let commit = repo.find_commit(oid)?;
let parent_id = first_parent_id(&commit)?;
let mut has_patch_match = false;
for candidate in &target.candidates {
for (target_index, candidate) in target.candidates.iter().enumerate() {
let Some(candidate_patch_id) =
patch_id_cache.get(&candidate.id).and_then(|v| v.as_ref())
else {
Expand All @@ -1000,19 +1052,23 @@ pub fn find_floating_base(
if candidate_patch_id != &patch_id {
continue;
}
if floating_parent_matches_candidate(
let parent_matches = floating_parent_matches_candidate(
repo,
parent_id,
candidate.parent_id,
patch_id_cache,
)? || is_tip_patch_rewrite(&commit, candidate, target_id)
{
has_patch_match = true;
break;
)?;
if !(parent_matches || is_tip_patch_rewrite(&commit, candidate, target_id)) {
continue;
}

let matching = FloatingBaseMatch {
branch_id: oid,
target_index,
};
if validate_floating_match(repo, branch_tip, matching, target, patch_id_cache)? {
return Ok(Some(matching));
}
}
if has_patch_match {
return Ok(Some(oid));
}
}

Expand Down Expand Up @@ -1113,9 +1169,9 @@ fn metadata_matches_target_candidate(
commit: &Commit,
oid: Oid,
target: &FloatingTargetContext,
) -> Result<bool> {
) -> Result<Option<usize>> {
if !target.reflog_ids.contains(&oid) {
return Ok(false);
return Ok(None);
}

let summary = commit.summary().unwrap_or("").trim();
Expand All @@ -1127,11 +1183,123 @@ fn metadata_matches_target_candidate(
None
};

Ok(target.candidates.iter().any(|candidate| {
Ok(target.candidates.iter().position(|candidate| {
candidate.summary == summary && candidate.email == email && candidate.parent_id == parent_id
}))
}

fn validate_floating_match(
repo: &Repository,
branch_tip: Oid,
matching: FloatingBaseMatch,
target: &FloatingTargetContext,
patch_id_cache: &mut HashMap<Oid, Option<String>>,
) -> Result<bool> {
let Some(target_tip) = target.candidates.first().map(|candidate| candidate.id) else {
return Ok(false);
};
let branch_chain = match repo.merge_base(branch_tip, target_tip) {
Ok(graph_merge_base) => collect_first_parent_chain(repo, graph_merge_base, branch_tip)?,
Err(_) => collect_first_parent_chain_to_root(repo, branch_tip)?,
};
let Some(match_index) = branch_chain
.iter()
.position(|oid| *oid == matching.branch_id)
else {
return Ok(false);
};

// Floating branches must have at least one commit ahead of the matched old base.
if match_index + 1 >= branch_chain.len() {
return Ok(false);
}

let mut chain_len = 1usize;
let mut branch_index = match_index;
let mut target_index = matching.target_index;

while branch_index > 0 && target_index + 1 < target.candidates.len() {
let branch_oid = branch_chain[branch_index - 1];
let candidate = &target.candidates[target_index + 1];
if !branch_commit_matches_target_candidate(
repo,
branch_oid,
candidate,
target,
patch_id_cache,
)? {
break;
}
chain_len += 1;
branch_index -= 1;
target_index += 1;
}

if chain_len >= 2 {
return Ok(true);
}

// Fallback: a single matched point is enough only when it is the branch's immediate
// fork point above the graph merge-base, meaning all newer commits belong to the suffix
// that should be replayed.
Ok(match_index == 0)
}

fn collect_first_parent_chain_to_root(repo: &Repository, tip: Oid) -> Result<Vec<Oid>> {
let mut chain = Vec::new();
let mut current = Some(tip);

while let Some(oid) = current {
chain.push(oid);
let commit = repo.find_commit(oid)?;
current = if commit.parent_count() > 0 {
Some(commit.parent_id(0)?)
} else {
None
};
}

chain.reverse();
Ok(chain)
}

fn branch_commit_matches_target_candidate(
repo: &Repository,
branch_oid: Oid,
candidate: &FloatingTargetCandidate,
target: &FloatingTargetContext,
patch_id_cache: &mut HashMap<Oid, Option<String>>,
) -> Result<bool> {
if branch_oid == candidate.id {
return Ok(true);
}

let branch_commit = repo.find_commit(branch_oid)?;
if branch_commit.tree_id() == candidate.tree_id {
return Ok(true);
}

ensure_patch_ids(repo, &[branch_oid, candidate.id], patch_id_cache)?;
let branch_patch_id = patch_id_cache
.get(&branch_oid)
.and_then(|value| value.as_ref());
let candidate_patch_id = patch_id_cache
.get(&candidate.id)
.and_then(|value| value.as_ref());
if branch_patch_id.is_some() && branch_patch_id == candidate_patch_id {
return Ok(true);
}

if target.reflog_ids.contains(&branch_oid)
&& candidate.summary == branch_commit.summary().unwrap_or("").trim()
&& candidate.email == branch_commit.author().email().unwrap_or("")
{
return Ok(true);
}

Ok(false)
}

fn read_branch_reflog_ids(repo: &Repository, branch_name: &str) -> HashSet<Oid> {
let reflog_name = if branch_name.starts_with("refs/") {
branch_name.to_string()
Expand Down
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