aboutsummaryrefslogtreecommitdiffstats
path: root/_examples/ls/main.go
blob: 95a0c60f1260b0e620bc7badd28adb8c45e8089b (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
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
}