Create merge-base feature

plumbing/object/commit_walker_bfs_filtered.go

@@ -0,0 +1,176 @@
+package object
+
+import (
+	"io"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/storer"
+)
+
+// NewFilterCommitIter returns a CommitIter that walks the commit history,
+// starting at the passed commit and visiting its parents in Breadth-first order.
+// The commits returned by the CommitIter will validate the passed CommitFilter.
+// The history won't be transversed beyond a commit if isLimit is true for it.
+// Each commit will be visited only once.
+// If the commit history can not be traversed, or the Close() method is called,
+// the CommitIter won't return more commits.
+// If no isValid is passed, all ancestors of from commit will be valid.
+// If no isLimit is limmit, all ancestors of all commits will be visited.
+func NewFilterCommitIter(
+	from *Commit,
+	isValid *CommitFilter,
+	isLimit *CommitFilter,
+) CommitIter {
+	var validFilter CommitFilter
+	if isValid == nil {
+		validFilter = func(_ *Commit) bool {
+			return true
+		}
+	} else {
+		validFilter = *isValid
+	}
+
+	var limitFilter CommitFilter
+	if isLimit == nil {
+		limitFilter = func(_ *Commit) bool {
+			return false
+		}
+	} else {
+		limitFilter = *isLimit
+	}
+
+	return &filterCommitIter{
+		isValid: validFilter,
+		isLimit: limitFilter,
+		visited: map[plumbing.Hash]struct{}{},
+		queue:   []*Commit{from},
+	}
+}
+
+// CommitFilter returns a boolean for the passed Commit
+type CommitFilter func(*Commit) bool
+
+// filterCommitIter implments CommitIter
+type filterCommitIter struct {
+	isValid CommitFilter
+	isLimit CommitFilter
+	visited map[plumbing.Hash]struct{}
+	queue   []*Commit
+	lastErr error
+}
+
+// Next returns the next commit of the CommitIter.
+// It will return io.EOF if there are no more commits to visit,
+// or an error if the history could not be traversed.
+func (w *filterCommitIter) Next() (*Commit, error) {
+	var commit *Commit
+	var err error
+	for {
+		commit, err = w.popNewFromQueue()
+		if err != nil {
+			return nil, w.close(err)
+		}
+
+		w.visited[commit.Hash] = struct{}{}
+
+		if !w.isLimit(commit) {
+			err = w.addToQueue(commit.s, commit.ParentHashes...)
+			if err != nil {
+				return nil, w.close(err)
+			}
+		}
+
+		if w.isValid(commit) {
+			return commit, nil
+		}
+	}
+}
+
+// ForEach runs the passed callback over each Commit returned by the CommitIter
+// until the callback returns an error or there is no more commits to traverse.
+func (w *filterCommitIter) ForEach(cb func(*Commit) error) error {
+	for {
+		commit, err := w.Next()
+		if err == io.EOF {
+			break
+		}
+
+		if err != nil {
+			return err
+		}
+
+		if err := cb(commit); err == storer.ErrStop {
+			break
+		} else if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// Error returns the error that caused that the CommitIter is no longer returning commits
+func (w *filterCommitIter) Error() error {
+	return w.lastErr
+}
+
+// Close closes the CommitIter
+func (w *filterCommitIter) Close() {
+	w.visited = map[plumbing.Hash]struct{}{}
+	w.queue = []*Commit{}
+	w.isLimit = nil
+	w.isValid = nil
+}
+
+// close closes the CommitIter with an error
+func (w *filterCommitIter) close(err error) error {
+	w.Close()
+	w.lastErr = err
+	return err
+}
+
+// popNewFromQueue returns the first new commit from the internal fifo queue,
+// or an io.EOF error if the queue is empty
+func (w *filterCommitIter) popNewFromQueue() (*Commit, error) {
+	var first *Commit
+	for {
+		if len(w.queue) == 0 {
+			if w.lastErr != nil {
+				return nil, w.lastErr
+			}
+
+			return nil, io.EOF
+		}
+
+		first = w.queue[0]
+		w.queue = w.queue[1:]
+		if _, ok := w.visited[first.Hash]; ok {
+			continue
+		}
+
+		return first, nil
+	}
+}
+
+// addToQueue adds the passed commits to the internal fifo queue if they weren't seen
+// or returns an error if the passed hashes could not be used to get valid commits
+func (w *filterCommitIter) addToQueue(
+	store storer.EncodedObjectStorer,
+	hashes ...plumbing.Hash,
+) error {
+	for _, hash := range hashes {
+		if _, ok := w.visited[hash]; ok {
+			continue
+		}
+
+		commit, err := GetCommit(store, hash)
+		if err != nil {
+			return err
+		}
+
+		w.queue = append(w.queue, commit)
+	}
+
+	return nil
+}
+