internal/gitutil/gitutil.go
349 lines · 13440 bytes
1// Package gitutil wraps the system git binary. All repository access goes
2// through git subprocesses; there is no in-process git implementation.
3package gitutil
4
5import (
6 "context"
7 "fmt"
8 "io"
9 "io/fs"
10 "os"
11 "os/exec"
12 "path/filepath"
13 "strings"
14
15 "gitbay.org/gitbay/internal/toolpath"
16)
17
18// InitBare creates a bare repository with the shared hooks directory wired
19// via core.hooksPath.
20func InitBare(path, defaultBranch, hooksPath string) error {
21 if err := os.MkdirAll(filepath.Dir(path), 0o750); err != nil {
22 return err
23 }
24 cmd := exec.Command(toolpath.Look("git"), "init", "--bare", "--initial-branch="+defaultBranch, path)
25 if out, err := cmd.CombinedOutput(); err != nil {
26 return fmt.Errorf("git init: %v\n%s", err, out)
27 }
28 cmd = exec.Command(toolpath.Look("git"), "-C", path, "config", "core.hooksPath", hooksPath)
29 if out, err := cmd.CombinedOutput(); err != nil {
30 return fmt.Errorf("git config core.hooksPath: %v\n%s", err, out)
31 }
32 return nil
33}
34
35// Transport streams one git transport service (upload-pack, receive-pack,
36// upload-archive). extraEnv entries are appended to the process environment;
37// hooks read the GITBAY_* variables from it. maxPack caps incoming pack
38// bytes on receive-pack (0 = unlimited), and keepAlive sets its
39// receive.keepAlive in seconds (0 = git's default). Closing cancel kills the service
40// and everything it started; a push killed before its pre-receive hook
41// answers updates no refs. A nil cancel never fires.
42func Transport(service, repoPath string, stdin io.Reader, stdout, errW io.Writer, extraEnv []string, maxPack int64, keepAlive int, cancel <-chan struct{}) error {
43 var args []string
44 switch service {
45 case "git-upload-pack", "git-receive-pack", "git-upload-archive":
46 if service == "git-receive-pack" && maxPack > 0 {
47 args = []string{"-c", fmt.Sprintf("receive.maxInputSize=%d", maxPack)}
48 }
49 if service == "git-receive-pack" && keepAlive > 0 {
50 // Seconds of silence after which receive-pack sends a
51 // keepalive while it indexes the pack and runs hooks.
52 args = append(args, "-c", fmt.Sprintf("receive.keepAlive=%d", keepAlive))
53 }
54 if service == "git-upload-pack" {
55 // Keepalives while pack-objects is still counting keep a
56 // healthy clone writing; a limited transport kills one that goes quiet.
57 args = []string{"-c", "uploadpack.keepAlive=5"}
58 }
59 args = append(args, strings.TrimPrefix(service, "git-"), repoPath)
60 default:
61 return fmt.Errorf("unknown service %q", service)
62 }
63 cmd := exec.Command(toolpath.Look("git"), args...)
64 cmd.Env = append(os.Environ(), extraEnv...)
65 cmd.Stdin = stdin
66 cmd.Stdout = stdout
67 cmd.Stderr = errW
68 return RunUntil(cmd, cancel)
69}
70
71// RunUntil runs cmd in its own process group. Closing cancel kills the
72// group; RunUntil returns only once cmd has been waited for. A nil
73// cancel never fires.
74func RunUntil(cmd *exec.Cmd, cancel <-chan struct{}) error {
75 ownProcessGroup(cmd)
76 if err := cmd.Start(); err != nil {
77 return err
78 }
79 finished := make(chan struct{})
80 go func() {
81 select {
82 case <-cancel:
83 killTree(cmd)
84 case <-finished:
85 }
86 }()
87 err := cmd.Wait()
88 close(finished)
89 return err
90}
91
92// IsAncestor reports whether old is an ancestor of new in the repository at
93// dir. It must run with the caller's environment intact so that quarantined
94// objects during pre-receive remain visible.
95func IsAncestor(dir, old, new string) (bool, error) {
96 cmd := exec.Command(toolpath.Look("git"), "-C", dir, "merge-base", "--is-ancestor", old, new)
97 err := cmd.Run()
98 if err == nil {
99 return true, nil
100 }
101 if ee, ok := err.(*exec.ExitError); ok && ee.ExitCode() == 1 {
102 return false, nil
103 }
104 return false, err
105}
106
107// Reachable reports whether sha is reachable from some ref in the
108// repository at dir — the condition a clone must find true to have any
109// chance of checking it out. That includes refs outside refs/heads and
110// refs/tags: a merge request head fetched from a fork lives at
111// refs/merge-requests/<n>/head, and is exactly as fetchable as a branch
112// tip, so it must count as reachable too — a first pass of this function
113// restricted the check to branches and tags and read every fork MR's
114// queued build as unreachable, cancelling it. false comes from two
115// shapes, and Reachable does not need to tell them apart: the object is
116// already gone (pruned), or it is still in the object store but nothing
117// points at it any more (a force-push moved the branch, gc has not run
118// yet). Either way the answer is the same: no ref reaches it.
119//
120// A non-nil error means the check itself did not run to a clean answer —
121// missing repository, git failing for its own reasons — and false is
122// meaningless in that case. The caller must not read err as "unreachable":
123// that would cancel a build the check never actually looked at.
124func Reachable(dir, sha string) (bool, error) {
125 if _, err := os.Stat(dir); err != nil {
126 return false, fmt.Errorf("reachable %s: %w", sha, err)
127 }
128 // cat-file -e <object>, unpeeled, is git's own existence predicate with
129 // a documented exit code: 1 means the object is not there, the same
130 // contract IsAncestor above already trusts from merge-base
131 // --is-ancestor. Peeling to ^{commit} breaks that contract: a missing
132 // object then exits 128, indistinguishable from "not a git repository"
133 // or a corrupted one — the ambiguous case that must never read as
134 // "unreachable" and cancel a build the check never actually looked at.
135 err := exec.Command(toolpath.Look("git"), "-C", dir, "cat-file", "-e", "--end-of-options", sha).Run()
136 if err != nil {
137 if ee, ok := err.(*exec.ExitError); ok && ee.ExitCode() == 1 {
138 return false, nil
139 }
140 return false, fmt.Errorf("cat-file -e %s: %w", sha, err)
141 }
142 // The object exists; --contains lists every ref whose history includes
143 // it, with no namespace restriction — a branch, a tag, or a
144 // refs/merge-requests/<n>/head are equally "a ref reaches this", and
145 // that is the actual question, not whether it happens to be a branch
146 // or a tag. Empty output with no error is the force-push case: present
147 // in the object store, reachable from nothing.
148 out, err := exec.Command(toolpath.Look("git"), "-C", dir, "for-each-ref",
149 "--count=1", "--format=x", "--contains="+sha).Output()
150 if err != nil {
151 return false, fmt.Errorf("for-each-ref --contains %s: %w", sha, err)
152 }
153 return len(out) > 0, nil
154}
155
156// ZeroSHA reports whether s is an all-zero object id (SHA-1 or SHA-256).
157func ZeroSHA(s string) bool {
158 if len(s) != 40 && len(s) != 64 {
159 return false
160 }
161 for i := 0; i < len(s); i++ {
162 if s[i] != '0' {
163 return false
164 }
165 }
166 return true
167}
168
169// RevList returns up to limit commit SHAs reachable from ref, newest first.
170func RevList(dir, ref string, limit int) ([]string, error) {
171 cmd := exec.Command(toolpath.Look("git"), "-C", dir, "rev-list", fmt.Sprintf("--max-count=%d", limit), "--end-of-options", ref)
172 out, err := cmd.Output()
173 if err != nil {
174 return nil, fmt.Errorf("rev-list %s: %w", ref, err)
175 }
176 var shas []string
177 for _, l := range strings.Split(strings.TrimSpace(string(out)), "\n") {
178 if l != "" {
179 shas = append(shas, l)
180 }
181 }
182 return shas, nil
183}
184
185// RevListPath returns up to limit commit SHAs reachable from ref that
186// touch filePath, newest first. The "--" keeps the path from ever being
187// read as an option or ref.
188func RevListPath(dir, ref, filePath string, limit int) ([]string, error) {
189 cmd := exec.Command(toolpath.Look("git"), "-C", dir, "rev-list",
190 fmt.Sprintf("--max-count=%d", limit), "--end-of-options", ref, "--", filePath)
191 out, err := cmd.Output()
192 if err != nil {
193 return nil, fmt.Errorf("rev-list %s -- %s: %w", ref, filePath, err)
194 }
195 var shas []string
196 for _, l := range strings.Split(strings.TrimSpace(string(out)), "\n") {
197 if l != "" {
198 shas = append(shas, l)
199 }
200 }
201 return shas, nil
202}
203
204// PeelToCommit resolves a ref or object to its commit — annotated tags
205// peel to the commit they point at.
206func PeelToCommit(dir, ref string) (string, error) {
207 out, err := exec.Command(toolpath.Look("git"), "-C", dir, "rev-parse", "--verify", "--end-of-options", ref+"^{commit}").Output()
208 if err != nil {
209 return "", fmt.Errorf("rev-parse %s^{commit}: %w", ref, err)
210 }
211 return strings.TrimSpace(string(out)), nil
212}
213
214// ReadCommit returns the raw commit object bytes.
215func ReadCommit(dir, sha string) ([]byte, error) {
216 cmd := exec.Command(toolpath.Look("git"), "-C", dir, "cat-file", "commit", "--end-of-options", sha)
217 out, err := cmd.Output()
218 if err != nil {
219 return nil, fmt.Errorf("cat-file commit %s: %w", sha, err)
220 }
221 return out, nil
222}
223
224// FetchMirror pulls all branches, tags, and notes from a foreign URL into
225// the bare repository at dir, forcing updates. Progress streams to errW so
226// an interactive caller can watch. pin is git's leading -c options
227// (gitpin.Remote.Args); env is git's whole environment and carries
228// credentials via GIT_ASKPASS: the URL itself must never contain them.
229func FetchMirror(ctx context.Context, dir, url string, errW io.Writer, pin, env []string) error {
230 args := append(append([]string{}, pin...), "-C", dir, "fetch", "--progress", "--no-write-fetch-head", url,
231 "+refs/heads/*:refs/heads/*",
232 "+refs/tags/*:refs/tags/*",
233 "+refs/notes/*:refs/notes/*")
234 cmd := exec.CommandContext(ctx, toolpath.Look("git"), args...)
235 cmd.Env = env
236 cmd.Stderr = errW
237 if err := cmd.Run(); err != nil {
238 return fmt.Errorf("fetch from %s: %w", url, err)
239 }
240 return nil
241}
242
243// FetchPullHeads pulls a GitHub repository's pull-request heads into
244// refs/gh-pull/*, so an imported pull request has something to diff.
245// GitHub publishes every PR head at refs/pull/<n>/head on the git remote,
246// but a mirror made with the default refspecs does not carry them, which
247// is why an import used to produce merge requests with no head at all.
248//
249// One fetch for every pull request rather than one each: the ref count is
250// the repository's history, and asking a hundred times is a hundred
251// handshakes. pin and env are as for FetchMirror; env carries
252// credentials via GIT_ASKPASS, and the URL must never contain them.
253func FetchPullHeads(ctx context.Context, dir, url string, errW io.Writer, pin, env []string) error {
254 args := append(append([]string{}, pin...), "-C", dir, "fetch", "--no-write-fetch-head", "--no-tags",
255 url, "+refs/pull/*/head:refs/gh-pull/*")
256 cmd := exec.CommandContext(ctx, toolpath.Look("git"), args...)
257 cmd.Env = env
258 cmd.Stderr = errW
259 if err := cmd.Run(); err != nil {
260 return fmt.Errorf("fetch pull heads from %s: %w", url, err)
261 }
262 return nil
263}
264
265// RemoteDefaultBranch asks the remote which branch HEAD points at,
266// running in the repository at dir. pin and env are as for FetchMirror.
267func RemoteDefaultBranch(ctx context.Context, dir, url string, pin, env []string) (string, error) {
268 args := append(append([]string{}, pin...), "-C", dir, "ls-remote", "--symref", url, "HEAD")
269 cmd := exec.CommandContext(ctx, toolpath.Look("git"), args...)
270 cmd.Env = env
271 out, err := cmd.Output()
272 if err != nil {
273 return "", fmt.Errorf("ls-remote %s: %w", url, err)
274 }
275 // "ref: refs/heads/<branch>\tHEAD"
276 for _, line := range strings.Split(string(out), "\n") {
277 if rest, ok := strings.CutPrefix(line, "ref: refs/heads/"); ok {
278 if branch, _, ok := strings.Cut(rest, "\t"); ok {
279 return branch, nil
280 }
281 }
282 }
283 return "", fmt.Errorf("remote %s did not advertise a default branch", url)
284}
285
286// SetHead points the bare repo's HEAD at a branch.
287func SetHead(dir, branch string) error {
288 cmd := exec.Command(toolpath.Look("git"), "-C", dir, "symbolic-ref", "HEAD", "refs/heads/"+branch)
289 if out, err := cmd.CombinedOutput(); err != nil {
290 return fmt.Errorf("symbolic-ref: %v\n%s", err, out)
291 }
292 return nil
293}
294
295// gitDefaultDescription is the placeholder git init writes; treated as no
296// description at all.
297const gitDefaultDescription = "Unnamed repository; edit this file 'description' to name the repository."
298
299// ReadDescription returns the repo's description from the classic
300// <repo>.git/description file, empty for the git-init placeholder.
301func ReadDescription(dir string) string {
302 raw, err := os.ReadFile(filepath.Join(dir, "description"))
303 if err != nil {
304 return ""
305 }
306 desc := strings.TrimSpace(string(raw))
307 if desc == gitDefaultDescription {
308 return ""
309 }
310 return desc
311}
312
313// WriteDescription sets the description file: first line only, capped.
314func WriteDescription(dir, desc string) error {
315 desc, _, _ = strings.Cut(strings.TrimSpace(desc), "\n")
316 if len(desc) > 256 {
317 desc = desc[:256]
318 }
319 return os.WriteFile(filepath.Join(dir, "description"), []byte(desc+"\n"), 0o644)
320}
321
322// DirSize sums file sizes under dir; unreadable entries count as zero.
323func DirSize(dir string) int64 {
324 var total int64
325 filepath.WalkDir(dir, func(_ string, d fs.DirEntry, err error) error {
326 if err != nil || d.IsDir() {
327 return nil
328 }
329 if fi, err := d.Info(); err == nil {
330 total += fi.Size()
331 }
332 return nil
333 })
334 return total
335}
336
337// Every git this package runs prints paths as they are, not quoted with
338// octal escapes the way core.quotepath does by default, so a file called
339// übersicht.txt lists, greps, blames and diffs under its own name.
340// GIT_CONFIG_PARAMETERS reaches every subprocess, hooks included,
341// without touching each call site (#129).
342func init() {
343 const q = "'core.quotepath=off'"
344 if cur := os.Getenv("GIT_CONFIG_PARAMETERS"); cur != "" {
345 os.Setenv("GIT_CONFIG_PARAMETERS", cur+" "+q)
346 } else {
347 os.Setenv("GIT_CONFIG_PARAMETERS", q)
348 }
349}