package main
import (
"fmt"
"io"
"os"
"path"
"strings"
"github.com/emirpasic/gods/trees/binaryheap"
"github.com/go-git/go-git/v5"
. "github.com/go-git/go-git/v5/_examples"
"github.com/go-git/go-git/v5/plumbing"
"github.com/go-git/go-git/v5/plumbing/cache"
commitgraph_fmt "github.com/go-git/go-git/v5/plumbing/format/commitgraph"
"github.com/go-git/go-git/v5/plumbing/object"
"github.com/go-git/go-git/v5/plumbing/object/commitgraph"
"github.com/go-git/go-git/v5/storage/filesystem"
"github.com/go-git/go-billy/v5"
"github.com/go-git/go-billy/v5/osfs"
)
// Example how to resolve a revision into its commit counterpart
func main() {
CheckArgs("<path>", "<revision>", "<tree path>")
path := os.Args[1]
revision := os.Args[2]
treePath := os.Args[3]
// We instantiate a new repository targeting the given path (the .git folder)
fs := osfs.New(path)
if _, err := fs.Stat(git.GitDirName); err == nil {
fs, err = fs.Chroot(git.GitDirName)
CheckIfError(err)
}
s := filesystem.NewStorageWithOptions(fs, cache.NewObjectLRUDefault(), filesystem.Options{KeepDescriptors: true})
r, err := git.Open(s, fs)
CheckIfError(err)
defer s.Close()
// Resolve revision into a sha1 commit, only some revisions are resolved
// look at the doc to get more details
Info("git rev-parse %s", revision)
h, err := r.ResolveRevision(plumbing.Revision(revision))
CheckIfError(err)
commit, err := r.CommitObject(*h)
CheckIfError(err)
tree, err := commit.Tree()
CheckIfError(err)
if treePath != "" {
tree, err = tree.Tree(treePath)
CheckIfError(err)
}
var paths []string
for _, entry := range tree.Entries {
paths = append(paths, entry.Name)
}
commitNodeIndex, file := getCommitNodeIndex(r, fs)
if file != nil {
defer file.Close()
}
commitNode, err := commitNodeIndex.Get(*h)
CheckIfError(err)
revs, err := getLastCommitForPaths(commitNode, treePath, paths)
CheckIfError(err)
for path, rev := range revs {
// Print one line per file (name hash message)
hash := rev.Hash.String()
line := strings.Split(rev.Message, "\n")
fmt.Println(path, hash[:7], line[0])
}
}
func getCommitNodeIndex(r *git.Repository, fs billy.Filesystem) (commitgraph.CommitNodeIndex, io.ReadCloser) {
file, err := fs.Open(path.Join("objects", "info", "commit-graph"))
if err == nil {
index, err := commitgraph_fmt.OpenFileIndex(file)
if err == nil {
return commitgraph.NewGraphCommitNodeIndex(index, r.Storer), file
}
file.Close()
}
return commitgraph.NewObjectCommitNodeIndex(r.Storer), nil
}
type commitAndPaths struct {
commit commitgraph.CommitNode
// Paths that are still on the branch represented by commit
paths []string
// Set of hashes for the paths
hashes map[string]plumbing.Hash
}
func getCommitTree(c commitgraph.CommitNode, treePath string) (*object.Tree, error) {
tree, err := c.Tree()
if err != nil {
return nil, err
}
// Optimize deep traversals by focusing only on the specific tree
if treePath != "" {
tree, err = tree.Tree(treePath)
if err != nil {
return nil, err
}
}
return tree, nil
}
func getFullPath(treePath, path string) string {
if treePath != "" {
if path != "" {
return treePath + "/" + path
}
return treePath
}
return path
}
func getFileHashes(c commitgraph.CommitNode, treePath string, paths []string) (map[string]plumbing.Hash, error) {
tree, err := getCommitTree(c, treePath)
if err == object.ErrDirectoryNotFound {
// The whole tree didn't exist, so return empty map
return make(map[string]plumbing.Hash), nil
}
if err != nil {
return nil, err
}
hashes := make(map[string]plumbing.Hash)
for _, path := range paths {
if path != "" {
entry, err := tree.FindEntry(path)
if err == nil {
hashes[path] = entry.Hash
}
} else {
hashes[path] = tree.Hash
}
}
return hashes, nil
}
func getLastCommitForPaths(c commitgraph.CommitNode, treePath string, paths []string) (map[string]*object.Commit, error) {
// We do a tree traversal with nodes sorted by commit time
heap := binaryheap.NewWith(func(a, b interface{}) int {
if a.(*commitAndPaths).commit.CommitTime().Before(b.(*commitAndPaths).commit.CommitTime()) {
return 1
}
return -1
})
resultNodes := make(map[string]commitgraph.CommitNode)
initialHashes, err := getFileHashes(c, treePath, paths)
if err != nil {
return nil, err
}
// Start search from the root commit and with full set of paths
heap.Push(&commitAndPaths{c, paths, initialHashes})
for {
cIn, ok := heap.Pop()
if !ok {
break
}
current := cIn.(*commitAndPaths)
// Load the parent commits for the one we are currently examining
numParents := current.commit.NumParents()
var parents []commitgraph.CommitNode
for i := 0; i < numParents; i++ {
parent, err := current.commit.ParentNode(i)
if err != nil {
break
}
parents = append(parents, parent)
}
// Examine the current commit and set of interesting paths
pathUnchanged := make([]bool, len(current.paths))
parentHashes := make([]map[string]plumbing.Hash, len(parents))
for j, parent := range parents {
parentHashes[j], err = getFileHashes(parent, treePath, current.paths)
if err != nil {
break
}
for i, path := range current.paths {
if parentHashes[j][path] == current.hashes[path] {
pathUnchanged[i] = true
}
}
}
var remainingPaths []string
for i, path := range current.paths {
// The results could already contain some newer change for the same path,
// so don't override that and bail out on the file early.
if resultNodes[path] == nil {
if pathUnchanged[i] {
// The path existed with the same hash in at least one parent so it could
// not have been changed in this commit directly.
remainingPaths = append(remainingPaths, path)
} else {
// There are few possible cases how can we get here:
// - The path didn't exist in any parent, so it must have been created by
// this commit.
// - The path did exist in the parent commit, but the hash of the file has
// changed.
// - We are looking at a merge commit and the hash of the file doesn't
// match any of the hashes being merged. This is more common for directories,
// but it can also happen if a file is changed through conflict resolution.
resultNodes[path] = current.commit
}
}
}
if len(remainingPaths) > 0 {
// Add the parent nodes along with remaining paths to the heap for further
// processing.
for j, parent := range parents {
// Combine remainingPath with paths available on the parent branch
// and make union of them
remainingPathsForParent := make([]string, 0, len(remainingPaths))
newRemainingPaths := make([]string, 0, len(remainingPaths))
for _, path := range remainingPaths {
if parentHashes[j][path] == current.hashes[path] {
remainingPathsForParent = append(remainingPathsForParent, path)
} else {
newRemainingPaths = append(newRemainingPaths, path)
}
}
if remainingPathsForParent != nil {
heap.Push(&commitAndPaths{parent, remainingPathsForParent, parentHashes[j]})
}
if len(newRemainingPaths) == 0 {
break
} else {
remainingPaths = newRemainingPaths
}
}
}
}
// Post-processing
result := make(map[string]*object.Commit)
for path, commitNode := range resultNodes {
var err error
result[path], err = commitNode.Commit()
if err != nil {
return nil, err
}
}
return result, nil
}
