blob: 5673ac13566626fa0e5da765e71c02417e77a603 [file] [log] [blame]
package git
import (
"io"
"sort"
"gopkg.in/src-d/go-git.v4/plumbing"
"gopkg.in/src-d/go-git.v4/plumbing/object"
"gopkg.in/src-d/go-git.v4/utils/diff"
"github.com/sergi/go-diff/diffmatchpatch"
)
// References returns a slice of Commits for the file at "path", starting from
// the commit provided that contains the file from the provided path. The last
// commit into the returned slice is the commit where the file was created.
// If the provided commit does not contains the specified path, a nil slice is
// returned. The commits are sorted in commit order, newer to older.
//
// Caveats:
//
// - Moves and copies are not currently supported.
//
// - Cherry-picks are not detected unless there are no commits between them and
// therefore can appear repeated in the list. (see git path-id for hints on how
// to fix this).
func references(c *object.Commit, path string) ([]*object.Commit, error) {
var result []*object.Commit
seen := make(map[plumbing.Hash]struct{})
if err := walkGraph(&result, &seen, c, path); err != nil {
return nil, err
}
// TODO result should be returned without ordering
sortCommits(result)
// for merges of identical cherry-picks
return removeComp(path, result, equivalent)
}
type commitSorterer struct {
l []*object.Commit
}
func (s commitSorterer) Len() int {
return len(s.l)
}
func (s commitSorterer) Less(i, j int) bool {
return s.l[i].Committer.When.Before(s.l[j].Committer.When) ||
s.l[i].Committer.When.Equal(s.l[j].Committer.When) &&
s.l[i].Author.When.Before(s.l[j].Author.When)
}
func (s commitSorterer) Swap(i, j int) {
s.l[i], s.l[j] = s.l[j], s.l[i]
}
// SortCommits sorts a commit list by commit date, from older to newer.
func sortCommits(l []*object.Commit) {
s := &commitSorterer{l}
sort.Sort(s)
}
// Recursive traversal of the commit graph, generating a linear history of the
// path.
func walkGraph(result *[]*object.Commit, seen *map[plumbing.Hash]struct{}, current *object.Commit, path string) error {
// check and update seen
if _, ok := (*seen)[current.Hash]; ok {
return nil
}
(*seen)[current.Hash] = struct{}{}
// if the path is not in the current commit, stop searching.
if _, err := current.File(path); err != nil {
return nil
}
// optimization: don't traverse branches that does not
// contain the path.
parents, err := parentsContainingPath(path, current)
if err != nil {
return err
}
switch len(parents) {
// if the path is not found in any of its parents, the path was
// created by this commit; we must add it to the revisions list and
// stop searching. This includes the case when current is the
// initial commit.
case 0:
*result = append(*result, current)
return nil
case 1: // only one parent contains the path
// if the file contents has change, add the current commit
different, err := differentContents(path, current, parents)
if err != nil {
return err
}
if len(different) == 1 {
*result = append(*result, current)
}
// in any case, walk the parent
return walkGraph(result, seen, parents[0], path)
default: // more than one parent contains the path
// TODO: detect merges that had a conflict, because they must be
// included in the result here.
for _, p := range parents {
err := walkGraph(result, seen, p, path)
if err != nil {
return err
}
}
}
return nil
}
func parentsContainingPath(path string, c *object.Commit) ([]*object.Commit, error) {
// TODO: benchmark this method making git.object.Commit.parent public instead of using
// an iterator
var result []*object.Commit
iter := c.Parents()
for {
parent, err := iter.Next()
if err == io.EOF {
return result, nil
}
if err != nil {
return nil, err
}
if _, err := parent.File(path); err == nil {
result = append(result, parent)
}
}
}
// Returns an slice of the commits in "cs" that has the file "path", but with different
// contents than what can be found in "c".
func differentContents(path string, c *object.Commit, cs []*object.Commit) ([]*object.Commit, error) {
result := make([]*object.Commit, 0, len(cs))
h, found := blobHash(path, c)
if !found {
return nil, object.ErrFileNotFound
}
for _, cx := range cs {
if hx, found := blobHash(path, cx); found && h != hx {
result = append(result, cx)
}
}
return result, nil
}
// blobHash returns the hash of a path in a commit
func blobHash(path string, commit *object.Commit) (hash plumbing.Hash, found bool) {
file, err := commit.File(path)
if err != nil {
var empty plumbing.Hash
return empty, found
}
return file.Hash, true
}
type contentsComparatorFn func(path string, a, b *object.Commit) (bool, error)
// Returns a new slice of commits, with duplicates removed. Expects a
// sorted commit list. Duplication is defined according to "comp". It
// will always keep the first commit of a series of duplicated commits.
func removeComp(path string, cs []*object.Commit, comp contentsComparatorFn) ([]*object.Commit, error) {
result := make([]*object.Commit, 0, len(cs))
if len(cs) == 0 {
return result, nil
}
result = append(result, cs[0])
for i := 1; i < len(cs); i++ {
equals, err := comp(path, cs[i], cs[i-1])
if err != nil {
return nil, err
}
if !equals {
result = append(result, cs[i])
}
}
return result, nil
}
// Equivalent commits are commits whose patch is the same.
func equivalent(path string, a, b *object.Commit) (bool, error) {
numParentsA := a.NumParents()
numParentsB := b.NumParents()
// the first commit is not equivalent to anyone
// and "I think" merges can not be equivalent to anything
if numParentsA != 1 || numParentsB != 1 {
return false, nil
}
diffsA, err := patch(a, path)
if err != nil {
return false, err
}
diffsB, err := patch(b, path)
if err != nil {
return false, err
}
return sameDiffs(diffsA, diffsB), nil
}
func patch(c *object.Commit, path string) ([]diffmatchpatch.Diff, error) {
// get contents of the file in the commit
file, err := c.File(path)
if err != nil {
return nil, err
}
content, err := file.Contents()
if err != nil {
return nil, err
}
// get contents of the file in the first parent of the commit
var contentParent string
iter := c.Parents()
parent, err := iter.Next()
if err != nil {
return nil, err
}
file, err = parent.File(path)
if err != nil {
contentParent = ""
} else {
contentParent, err = file.Contents()
if err != nil {
return nil, err
}
}
// compare the contents of parent and child
return diff.Do(content, contentParent), nil
}
func sameDiffs(a, b []diffmatchpatch.Diff) bool {
if len(a) != len(b) {
return false
}
for i := range a {
if !sameDiff(a[i], b[i]) {
return false
}
}
return true
}
func sameDiff(a, b diffmatchpatch.Diff) bool {
if a.Type != b.Type {
return false
}
switch a.Type {
case 0:
return countLines(a.Text) == countLines(b.Text)
case 1, -1:
return a.Text == b.Text
default:
panic("unreachable")
}
}