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use crate::utils::hg_path::HgPath;
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use crate::utils::hg_path::HgPathBuf;
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use crate::Revision;
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use im_rc::ordmap::DiffItem;
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use im_rc::ordmap::OrdMap;
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use std::collections::HashMap;
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use std::collections::HashSet;
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pub type PathCopies = HashMap<HgPathBuf, HgPathBuf>;
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#[derive(Clone, Debug, PartialEq)]
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struct TimeStampedPathCopy {
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/// revision at which the copy information was added
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rev: Revision,
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/// the copy source, (Set to None in case of deletion of the associated
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/// key)
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path: Option<HgPathBuf>,
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}
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/// maps CopyDestination to Copy Source (+ a "timestamp" for the operation)
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type TimeStampedPathCopies = OrdMap<HgPathBuf, TimeStampedPathCopy>;
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/// hold parent 1, parent 2 and relevant files actions.
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pub type RevInfo = (Revision, Revision, ChangedFiles);
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/// represent the files affected by a changesets
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///
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/// This hold a subset of mercurial.metadata.ChangingFiles as we do not need
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/// all the data categories tracked by it.
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pub struct ChangedFiles {
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removed: HashSet<HgPathBuf>,
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merged: HashSet<HgPathBuf>,
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salvaged: HashSet<HgPathBuf>,
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copied_from_p1: PathCopies,
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copied_from_p2: PathCopies,
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}
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/// Represent active changes that affect the copy tracing.
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enum Action<'a> {
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/// The parent ? children edge is removing a file
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///
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/// (actually, this could be the edge from the other parent, but it does
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/// not matters)
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Removed(&'a HgPath),
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/// The parent ? children edge introduce copy information between (dest,
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/// source)
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Copied(&'a HgPath, &'a HgPath),
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}
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/// This express the possible "special" case we can get in a merge
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///
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/// See mercurial/metadata.py for details on these values.
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#[derive(PartialEq)]
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enum MergeCase {
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/// Merged: file had history on both side that needed to be merged
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Merged,
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/// Salvaged: file was candidate for deletion, but survived the merge
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Salvaged,
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/// Normal: Not one of the two cases above
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Normal,
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}
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impl ChangedFiles {
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pub fn new(
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removed: HashSet<HgPathBuf>,
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merged: HashSet<HgPathBuf>,
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salvaged: HashSet<HgPathBuf>,
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copied_from_p1: PathCopies,
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copied_from_p2: PathCopies,
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) -> Self {
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ChangedFiles {
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removed,
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merged,
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salvaged,
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copied_from_p1,
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copied_from_p2,
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}
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}
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pub fn new_empty() -> Self {
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ChangedFiles {
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removed: HashSet::new(),
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merged: HashSet::new(),
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salvaged: HashSet::new(),
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copied_from_p1: PathCopies::new(),
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copied_from_p2: PathCopies::new(),
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}
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}
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/// Return an iterator over all the `Action` in this instance.
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fn iter_actions(&self, parent: usize) -> impl Iterator<Item = Action> {
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let copies_iter = match parent {
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1 => self.copied_from_p1.iter(),
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2 => self.copied_from_p2.iter(),
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_ => unreachable!(),
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};
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let remove_iter = self.removed.iter();
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let copies_iter = copies_iter.map(|(x, y)| Action::Copied(x, y));
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let remove_iter = remove_iter.map(|x| Action::Removed(x));
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copies_iter.chain(remove_iter)
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}
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/// return the MergeCase value associated with a filename
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fn get_merge_case(&self, path: &HgPath) -> MergeCase {
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if self.salvaged.contains(path) {
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return MergeCase::Salvaged;
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} else if self.merged.contains(path) {
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return MergeCase::Merged;
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} else {
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return MergeCase::Normal;
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}
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}
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}
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/// A struct responsible for answering "is X ancestors of Y" quickly
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///
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/// The structure will delegate ancestors call to a callback, and cache the
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/// result.
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#[derive(Debug)]
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struct AncestorOracle<'a, A: Fn(Revision, Revision) -> bool> {
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inner: &'a A,
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pairs: HashMap<(Revision, Revision), bool>,
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}
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impl<'a, A: Fn(Revision, Revision) -> bool> AncestorOracle<'a, A> {
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fn new(func: &'a A) -> Self {
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Self {
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inner: func,
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pairs: HashMap::default(),
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}
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}
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/// returns `true` if `anc` is an ancestors of `desc`, `false` otherwise
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fn is_ancestor(&mut self, anc: Revision, desc: Revision) -> bool {
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if anc > desc {
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false
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} else if anc == desc {
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true
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} else {
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if let Some(b) = self.pairs.get(&(anc, desc)) {
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*b
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} else {
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let b = (self.inner)(anc, desc);
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self.pairs.insert((anc, desc), b);
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b
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}
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}
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}
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}
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/// Same as mercurial.copies._combine_changeset_copies, but in Rust.
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///
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/// Arguments are:
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///
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/// revs: all revisions to be considered
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/// children: a {parent ? [childrens]} mapping
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/// target_rev: the final revision we are combining copies to
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/// rev_info(rev): callback to get revision information:
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/// * first parent
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/// * second parent
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/// * ChangedFiles
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/// isancestors(low_rev, high_rev): callback to check if a revision is an
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/// ancestor of another
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pub fn combine_changeset_copies<A: Fn(Revision, Revision) -> bool>(
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revs: Vec<Revision>,
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children: HashMap<Revision, Vec<Revision>>,
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target_rev: Revision,
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rev_info: &impl Fn(Revision) -> RevInfo,
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is_ancestor: &A,
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) -> PathCopies {
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let mut all_copies = HashMap::new();
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let mut oracle = AncestorOracle::new(is_ancestor);
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for rev in revs {
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// Retrieve data computed in a previous iteration
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let copies = all_copies.remove(&rev);
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let copies = match copies {
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Some(c) => c,
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None => TimeStampedPathCopies::default(), // root of the walked set
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};
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let current_children = match children.get(&rev) {
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Some(c) => c,
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None => panic!("inconsistent `revs` and `children`"),
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};
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for child in current_children {
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// We will chain the copies information accumulated for `rev` with
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// the individual copies information for each of its children.
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// Creating a new PathCopies for each `rev` ? `children` vertex.
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let (p1, p2, changes) = rev_info(*child);
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let parent = if rev == p1 {
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1
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} else {
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assert_eq!(rev, p2);
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2
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};
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let mut new_copies = copies.clone();
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for action in changes.iter_actions(parent) {
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match action {
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Action::Copied(dest, source) => {
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let entry;
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if let Some(v) = copies.get(source) {
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entry = match &v.path {
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Some(path) => Some((*(path)).to_owned()),
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None => Some(source.to_owned()),
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}
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} else {
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entry = Some(source.to_owned());
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}
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// Each new entry is introduced by the children, we
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// record this information as we will need it to take
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// the right decision when merging conflicting copy
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// information. See merge_copies_dict for details.
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let ttpc = TimeStampedPathCopy {
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rev: *child,
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path: entry,
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};
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new_copies.insert(dest.to_owned(), ttpc);
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}
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Action::Removed(f) => {
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// We must drop copy information for removed file.
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//
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// We need to explicitly record them as dropped to
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// propagate this information when merging two
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// TimeStampedPathCopies object.
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if new_copies.contains_key(f.as_ref()) {
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let ttpc = TimeStampedPathCopy {
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rev: *child,
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path: None,
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};
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new_copies.insert(f.to_owned(), ttpc);
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}
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}
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}
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}
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// Merge has two parents needs to combines their copy information.
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//
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// If the vertex from the other parent was already processed, we
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// will have a value for the child ready to be used. We need to
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// grab it and combine it with the one we already
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// computed. If not we can simply store the newly
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// computed data. The processing happening at
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// the time of the second parent will take care of combining the
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// two TimeStampedPathCopies instance.
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match all_copies.remove(child) {
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None => {
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all_copies.insert(child, new_copies);
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}
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Some(other_copies) => {
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let (minor, major) = match parent {
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1 => (other_copies, new_copies),
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2 => (new_copies, other_copies),
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_ => unreachable!(),
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};
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let merged_copies =
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merge_copies_dict(minor, major, &changes, &mut oracle);
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all_copies.insert(child, merged_copies);
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}
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};
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}
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}
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// Drop internal information (like the timestamp) and return the final
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// mapping.
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let tt_result = all_copies
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.remove(&target_rev)
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.expect("target revision was not processed");
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let mut result = PathCopies::default();
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for (dest, tt_source) in tt_result {
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if let Some(path) = tt_source.path {
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result.insert(dest, path);
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}
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}
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result
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}
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/// merge two copies-mapping together, minor and major
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///
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/// In case of conflict, value from "major" will be picked, unless in some
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/// cases. See inline documentation for details.
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#[allow(clippy::if_same_then_else)]
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fn merge_copies_dict<A: Fn(Revision, Revision) -> bool>(
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minor: TimeStampedPathCopies,
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major: TimeStampedPathCopies,
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changes: &ChangedFiles,
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oracle: &mut AncestorOracle<A>,
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) -> TimeStampedPathCopies {
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if minor.is_empty() {
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return major;
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} else if major.is_empty() {
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return minor;
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}
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let mut override_minor = Vec::new();
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let mut override_major = Vec::new();
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let mut to_major = |k: &HgPathBuf, v: &TimeStampedPathCopy| {
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override_major.push((k.clone(), v.clone()))
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};
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let mut to_minor = |k: &HgPathBuf, v: &TimeStampedPathCopy| {
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override_minor.push((k.clone(), v.clone()))
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};
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// The diff function leverage detection of the identical subpart if minor
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// and major has some common ancestors. This make it very fast is most
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// case.
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//
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// In case where the two map are vastly different in size, the current
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// approach is still slowish because the iteration will iterate over
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// all the "exclusive" content of the larger on. This situation can be
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// frequent when the subgraph of revision we are processing has a lot
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// of roots. Each roots adding they own fully new map to the mix (and
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// likely a small map, if the path from the root to the "main path" is
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// small.
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//
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// We could do better by detecting such situation and processing them
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// differently.
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for d in minor.diff(&major) {
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match d {
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DiffItem::Add(k, v) => to_minor(k, v),
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DiffItem::Remove(k, v) => to_major(k, v),
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DiffItem::Update { old, new } => {
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let (dest, src_major) = new;
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let (_, src_minor) = old;
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let mut pick_minor = || (to_major(dest, src_minor));
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let mut pick_major = || (to_minor(dest, src_major));
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if src_major.path == src_minor.path {
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// we have the same value, but from other source;
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if src_major.rev == src_minor.rev {
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// If the two entry are identical, no need to do
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// anything (but diff should not have yield them)
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unreachable!();
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} else if oracle.is_ancestor(src_major.rev, src_minor.rev)
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{
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pick_minor();
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} else {
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pick_major();
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}
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} else if src_major.rev == src_minor.rev {
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// We cannot get copy information for both p1 and p2 in the
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// same rev. So this is the same value.
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unreachable!();
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} else {
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let action = changes.get_merge_case(&dest);
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if src_major.path.is_none()
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&& action == MergeCase::Salvaged
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{
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// If the file is "deleted" in the major side but was
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// salvaged by the merge, we keep the minor side alive
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pick_minor();
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} else if src_minor.path.is_none()
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&& action == MergeCase::Salvaged
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{
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// If the file is "deleted" in the minor side but was
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// salvaged by the merge, unconditionnaly preserve the
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// major side.
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pick_major();
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} else if action == MergeCase::Merged {
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// If the file was actively merged, copy information
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// from each side might conflict. The major side will
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// win such conflict.
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pick_major();
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} else if oracle.is_ancestor(src_major.rev, src_minor.rev)
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{
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// If the minor side is strictly newer than the major
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// side, it should be kept.
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pick_minor();
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} else if src_major.path.is_some() {
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// without any special case, the "major" value win
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// other the "minor" one.
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pick_major();
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} else if oracle.is_ancestor(src_minor.rev, src_major.rev)
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{
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// the "major" rev is a direct ancestors of "minor",
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// any different value should
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// overwrite
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pick_major();
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} else {
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// major version is None (so the file was deleted on
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// that branch) and that branch is independant (neither
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// minor nor major is an ancestors of the other one.)
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// We preserve the new
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// information about the new file.
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pick_minor();
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}
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}
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}
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};
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}
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let updates;
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let mut result;
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if override_major.is_empty() {
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result = major
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} else if override_minor.is_empty() {
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result = minor
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} else {
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if override_minor.len() < override_major.len() {
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updates = override_minor;
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result = minor;
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} else {
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updates = override_major;
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result = major;
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}
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for (k, v) in updates {
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result.insert(k, v);
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}
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}
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result
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}
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