blob: 7d9e5d82f9cc56a65b0505bb017f489d03a2aa0a [file] [log] [blame]
// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package codehost
import (
"bytes"
"context"
"crypto/sha256"
"encoding/base64"
"errors"
"fmt"
"io"
"io/fs"
"net/url"
"os"
"os/exec"
"path/filepath"
"runtime"
"slices"
"sort"
"strconv"
"strings"
"sync"
"time"
"cmd/go/internal/base"
"cmd/go/internal/lockedfile"
"cmd/go/internal/par"
"cmd/go/internal/web"
"golang.org/x/mod/semver"
)
// LocalGitRepo is like Repo but accepts both Git remote references
// and paths to repositories on the local file system.
func LocalGitRepo(ctx context.Context, remote string) (Repo, error) {
return newGitRepoCached(ctx, remote, true)
}
// A notExistError wraps another error to retain its original text
// but makes it opaquely equivalent to fs.ErrNotExist.
type notExistError struct {
err error
}
func (e notExistError) Error() string { return e.err.Error() }
func (notExistError) Is(err error) bool { return err == fs.ErrNotExist }
const gitWorkDirType = "git3"
var gitRepoCache par.ErrCache[gitCacheKey, Repo]
type gitCacheKey struct {
remote string
localOK bool
}
func newGitRepoCached(ctx context.Context, remote string, localOK bool) (Repo, error) {
return gitRepoCache.Do(gitCacheKey{remote, localOK}, func() (Repo, error) {
return newGitRepo(ctx, remote, localOK)
})
}
func newGitRepo(ctx context.Context, remote string, localOK bool) (Repo, error) {
r := &gitRepo{remote: remote}
if strings.Contains(remote, "://") {
// This is a remote path.
var err error
r.dir, r.mu.Path, err = WorkDir(ctx, gitWorkDirType, r.remote)
if err != nil {
return nil, err
}
unlock, err := r.mu.Lock()
if err != nil {
return nil, err
}
defer unlock()
if _, err := os.Stat(filepath.Join(r.dir, "objects")); err != nil {
if _, err := Run(ctx, r.dir, "git", "init", "--bare"); err != nil {
os.RemoveAll(r.dir)
return nil, err
}
// We could just say git fetch https://whatever later,
// but this lets us say git fetch origin instead, which
// is a little nicer. More importantly, using a named remote
// avoids a problem with Git LFS. See golang.org/issue/25605.
if _, err := Run(ctx, r.dir, "git", "remote", "add", "origin", "--", r.remote); err != nil {
os.RemoveAll(r.dir)
return nil, err
}
if runtime.GOOS == "windows" {
// Git for Windows by default does not support paths longer than
// MAX_PATH (260 characters) because that may interfere with navigation
// in some Windows programs. However, cmd/go should be able to handle
// long paths just fine, and we expect people to use 'go clean' to
// manipulate the module cache, so it should be harmless to set here,
// and in some cases may be necessary in order to download modules with
// long branch names.
//
// See https://github.com/git-for-windows/git/wiki/Git-cannot-create-a-file-or-directory-with-a-long-path.
if _, err := Run(ctx, r.dir, "git", "config", "core.longpaths", "true"); err != nil {
os.RemoveAll(r.dir)
return nil, err
}
}
}
r.remoteURL = r.remote
r.remote = "origin"
} else {
// Local path.
// Disallow colon (not in ://) because sometimes
// that's rcp-style host:path syntax and sometimes it's not (c:\work).
// The go command has always insisted on URL syntax for ssh.
if strings.Contains(remote, ":") {
return nil, fmt.Errorf("git remote cannot use host:path syntax")
}
if !localOK {
return nil, fmt.Errorf("git remote must not be local directory")
}
r.local = true
info, err := os.Stat(remote)
if err != nil {
return nil, err
}
if !info.IsDir() {
return nil, fmt.Errorf("%s exists but is not a directory", remote)
}
r.dir = remote
r.mu.Path = r.dir + ".lock"
}
return r, nil
}
type gitRepo struct {
ctx context.Context
remote, remoteURL string
local bool
dir string
mu lockedfile.Mutex // protects fetchLevel and git repo state
fetchLevel int
statCache par.ErrCache[string, *RevInfo]
refsOnce sync.Once
// refs maps branch and tag refs (e.g., "HEAD", "refs/heads/master")
// to commits (e.g., "37ffd2e798afde829a34e8955b716ab730b2a6d6")
refs map[string]string
refsErr error
localTagsOnce sync.Once
localTags sync.Map // map[string]bool
}
const (
// How much have we fetched into the git repo (in this process)?
fetchNone = iota // nothing yet
fetchSome // shallow fetches of individual hashes
fetchAll // "fetch -t origin": get all remote branches and tags
)
// loadLocalTags loads tag references from the local git cache
// into the map r.localTags.
func (r *gitRepo) loadLocalTags(ctx context.Context) {
// The git protocol sends all known refs and ls-remote filters them on the client side,
// so we might as well record both heads and tags in one shot.
// Most of the time we only care about tags but sometimes we care about heads too.
out, err := Run(ctx, r.dir, "git", "tag", "-l")
if err != nil {
return
}
for _, line := range strings.Split(string(out), "\n") {
if line != "" {
r.localTags.Store(line, true)
}
}
}
func (r *gitRepo) CheckReuse(ctx context.Context, old *Origin, subdir string) error {
if old == nil {
return fmt.Errorf("missing origin")
}
if old.VCS != "git" || old.URL != r.remoteURL {
return fmt.Errorf("origin moved from %v %q to %v %q", old.VCS, old.URL, "git", r.remoteURL)
}
if old.Subdir != subdir {
return fmt.Errorf("origin moved from %v %q %q to %v %q %q", old.VCS, old.URL, old.Subdir, "git", r.remoteURL, subdir)
}
// Note: Can have Hash with no Ref and no TagSum and no RepoSum,
// meaning the Hash simply has to remain in the repo.
// In that case we assume it does in the absence of any real way to check.
// But if neither Hash nor TagSum is present, we have nothing to check,
// which we take to mean we didn't record enough information to be sure.
if old.Hash == "" && old.TagSum == "" && old.RepoSum == "" {
return fmt.Errorf("non-specific origin")
}
r.loadRefs(ctx)
if r.refsErr != nil {
return r.refsErr
}
if old.Ref != "" {
hash, ok := r.refs[old.Ref]
if !ok {
return fmt.Errorf("ref %q deleted", old.Ref)
}
if hash != old.Hash {
return fmt.Errorf("ref %q moved from %s to %s", old.Ref, old.Hash, hash)
}
}
if old.TagSum != "" {
tags, err := r.Tags(ctx, old.TagPrefix)
if err != nil {
return err
}
if tags.Origin.TagSum != old.TagSum {
return fmt.Errorf("tags changed")
}
}
if old.RepoSum != "" {
if r.repoSum(r.refs) != old.RepoSum {
return fmt.Errorf("refs changed")
}
}
return nil
}
// loadRefs loads heads and tags references from the remote into the map r.refs.
// The result is cached in memory.
func (r *gitRepo) loadRefs(ctx context.Context) (map[string]string, error) {
r.refsOnce.Do(func() {
// The git protocol sends all known refs and ls-remote filters them on the client side,
// so we might as well record both heads and tags in one shot.
// Most of the time we only care about tags but sometimes we care about heads too.
release, err := base.AcquireNet()
if err != nil {
r.refsErr = err
return
}
out, gitErr := Run(ctx, r.dir, "git", "ls-remote", "-q", r.remote)
release()
if gitErr != nil {
if rerr, ok := gitErr.(*RunError); ok {
if bytes.Contains(rerr.Stderr, []byte("fatal: could not read Username")) {
rerr.HelpText = "Confirm the import path was entered correctly.\nIf this is a private repository, see https://golang.org/doc/faq#git_https for additional information."
}
}
// If the remote URL doesn't exist at all, ideally we should treat the whole
// repository as nonexistent by wrapping the error in a notExistError.
// For HTTP and HTTPS, that's easy to detect: we'll try to fetch the URL
// ourselves and see what code it serves.
if u, err := url.Parse(r.remoteURL); err == nil && (u.Scheme == "http" || u.Scheme == "https") {
if _, err := web.GetBytes(u); errors.Is(err, fs.ErrNotExist) {
gitErr = notExistError{gitErr}
}
}
r.refsErr = gitErr
return
}
refs := make(map[string]string)
for _, line := range strings.Split(string(out), "\n") {
f := strings.Fields(line)
if len(f) != 2 {
continue
}
if f[1] == "HEAD" || strings.HasPrefix(f[1], "refs/heads/") || strings.HasPrefix(f[1], "refs/tags/") {
refs[f[1]] = f[0]
}
}
for ref, hash := range refs {
if k, found := strings.CutSuffix(ref, "^{}"); found { // record unwrapped annotated tag as value of tag
refs[k] = hash
delete(refs, ref)
}
}
r.refs = refs
})
return r.refs, r.refsErr
}
func (r *gitRepo) Tags(ctx context.Context, prefix string) (*Tags, error) {
refs, err := r.loadRefs(ctx)
if err != nil {
return nil, err
}
tags := &Tags{
Origin: &Origin{
VCS: "git",
URL: r.remoteURL,
TagPrefix: prefix,
},
List: []Tag{},
}
for ref, hash := range refs {
if !strings.HasPrefix(ref, "refs/tags/") {
continue
}
tag := ref[len("refs/tags/"):]
if !strings.HasPrefix(tag, prefix) {
continue
}
tags.List = append(tags.List, Tag{tag, hash})
}
sort.Slice(tags.List, func(i, j int) bool {
return tags.List[i].Name < tags.List[j].Name
})
dir := prefix[:strings.LastIndex(prefix, "/")+1]
h := sha256.New()
for _, tag := range tags.List {
if isOriginTag(strings.TrimPrefix(tag.Name, dir)) {
fmt.Fprintf(h, "%q %s\n", tag.Name, tag.Hash)
}
}
tags.Origin.TagSum = "t1:" + base64.StdEncoding.EncodeToString(h.Sum(nil))
return tags, nil
}
// repoSum returns a checksum of the entire repo state,
// which can be checked (as Origin.RepoSum) to cache
// the absence of a specific module version.
// The caller must supply refs, the result of a successful r.loadRefs.
func (r *gitRepo) repoSum(refs map[string]string) string {
var list []string
for ref := range refs {
list = append(list, ref)
}
sort.Strings(list)
h := sha256.New()
for _, ref := range list {
fmt.Fprintf(h, "%q %s\n", ref, refs[ref])
}
return "r1:" + base64.StdEncoding.EncodeToString(h.Sum(nil))
}
// unknownRevisionInfo returns a RevInfo containing an Origin containing a RepoSum of refs,
// for use when returning an UnknownRevisionError.
func (r *gitRepo) unknownRevisionInfo(refs map[string]string) *RevInfo {
return &RevInfo{
Origin: &Origin{
VCS: "git",
URL: r.remoteURL,
RepoSum: r.repoSum(refs),
},
}
}
func (r *gitRepo) Latest(ctx context.Context) (*RevInfo, error) {
refs, err := r.loadRefs(ctx)
if err != nil {
return nil, err
}
if refs["HEAD"] == "" {
return nil, ErrNoCommits
}
statInfo, err := r.Stat(ctx, refs["HEAD"])
if err != nil {
return nil, err
}
// Stat may return cached info, so make a copy to modify here.
info := new(RevInfo)
*info = *statInfo
info.Origin = new(Origin)
if statInfo.Origin != nil {
*info.Origin = *statInfo.Origin
}
info.Origin.Ref = "HEAD"
info.Origin.Hash = refs["HEAD"]
return info, nil
}
// findRef finds some ref name for the given hash,
// for use when the server requires giving a ref instead of a hash.
// There may be multiple ref names for a given hash,
// in which case this returns some name - it doesn't matter which.
func (r *gitRepo) findRef(ctx context.Context, hash string) (ref string, ok bool) {
refs, err := r.loadRefs(ctx)
if err != nil {
return "", false
}
for ref, h := range refs {
if h == hash {
return ref, true
}
}
return "", false
}
// minHashDigits is the minimum number of digits to require
// before accepting a hex digit sequence as potentially identifying
// a specific commit in a git repo. (Of course, users can always
// specify more digits, and many will paste in all 40 digits,
// but many of git's commands default to printing short hashes
// as 7 digits.)
const minHashDigits = 7
// stat stats the given rev in the local repository,
// or else it fetches more info from the remote repository and tries again.
func (r *gitRepo) stat(ctx context.Context, rev string) (info *RevInfo, err error) {
if r.local {
return r.statLocal(ctx, rev, rev)
}
// Fast path: maybe rev is a hash we already have locally.
didStatLocal := false
if len(rev) >= minHashDigits && len(rev) <= 40 && AllHex(rev) {
if info, err := r.statLocal(ctx, rev, rev); err == nil {
return info, nil
}
didStatLocal = true
}
// Maybe rev is a tag we already have locally.
// (Note that we're excluding branches, which can be stale.)
r.localTagsOnce.Do(func() { r.loadLocalTags(ctx) })
if _, ok := r.localTags.Load(rev); ok {
return r.statLocal(ctx, rev, "refs/tags/"+rev)
}
// Maybe rev is the name of a tag or branch on the remote server.
// Or maybe it's the prefix of a hash of a named ref.
// Try to resolve to both a ref (git name) and full (40-hex-digit) commit hash.
refs, err := r.loadRefs(ctx)
if err != nil {
return nil, err
}
// loadRefs may return an error if git fails, for example segfaults, or
// could not load a private repo, but defer checking to the else block
// below, in case we already have the rev in question in the local cache.
var ref, hash string
if refs["refs/tags/"+rev] != "" {
ref = "refs/tags/" + rev
hash = refs[ref]
// Keep rev as is: tags are assumed not to change meaning.
} else if refs["refs/heads/"+rev] != "" {
ref = "refs/heads/" + rev
hash = refs[ref]
rev = hash // Replace rev, because meaning of refs/heads/foo can change.
} else if rev == "HEAD" && refs["HEAD"] != "" {
ref = "HEAD"
hash = refs[ref]
rev = hash // Replace rev, because meaning of HEAD can change.
} else if len(rev) >= minHashDigits && len(rev) <= 40 && AllHex(rev) {
// At the least, we have a hash prefix we can look up after the fetch below.
// Maybe we can map it to a full hash using the known refs.
prefix := rev
// Check whether rev is prefix of known ref hash.
for k, h := range refs {
if strings.HasPrefix(h, prefix) {
if hash != "" && hash != h {
// Hash is an ambiguous hash prefix.
// More information will not change that.
return nil, fmt.Errorf("ambiguous revision %s", rev)
}
if ref == "" || ref > k { // Break ties deterministically when multiple refs point at same hash.
ref = k
}
rev = h
hash = h
}
}
if hash == "" && len(rev) == 40 { // Didn't find a ref, but rev is a full hash.
hash = rev
}
} else {
return r.unknownRevisionInfo(refs), &UnknownRevisionError{Rev: rev}
}
defer func() {
if info != nil {
info.Origin.Hash = info.Name
// There's a ref = hash below; don't write that hash down as Origin.Ref.
if ref != info.Origin.Hash {
info.Origin.Ref = ref
}
}
}()
// Protect r.fetchLevel and the "fetch more and more" sequence.
unlock, err := r.mu.Lock()
if err != nil {
return nil, err
}
defer unlock()
// Perhaps r.localTags did not have the ref when we loaded local tags,
// but we've since done fetches that pulled down the hash we need
// (or already have the hash we need, just without its tag).
// Either way, try a local stat before falling back to network I/O.
if !didStatLocal {
if info, err := r.statLocal(ctx, rev, hash); err == nil {
tag, fromTag := strings.CutPrefix(ref, "refs/tags/")
if fromTag && !slices.Contains(info.Tags, tag) {
// The local repo includes the commit hash we want, but it is missing
// the corresponding tag. Add that tag and try again.
_, err := Run(ctx, r.dir, "git", "tag", tag, hash)
if err != nil {
return nil, err
}
r.localTags.Store(tag, true)
return r.statLocal(ctx, rev, ref)
}
return info, err
}
}
// If we know a specific commit we need and its ref, fetch it.
// We do NOT fetch arbitrary hashes (when we don't know the ref)
// because we want to avoid ever importing a commit that isn't
// reachable from refs/tags/* or refs/heads/* or HEAD.
// Both Gerrit and GitHub expose every CL/PR as a named ref,
// and we don't want those commits masquerading as being real
// pseudo-versions in the main repo.
if r.fetchLevel <= fetchSome && ref != "" && hash != "" && !r.local {
r.fetchLevel = fetchSome
var refspec string
if ref == "HEAD" {
// Fetch the hash but give it a local name (refs/dummy),
// because that triggers the fetch behavior of creating any
// other known remote tags for the hash. We never use
// refs/dummy (it's not refs/tags/dummy) and it will be
// overwritten in the next command, and that's fine.
ref = hash
refspec = hash + ":refs/dummy"
} else {
// If we do know the ref name, save the mapping locally
// so that (if it is a tag) it can show up in localTags
// on a future call. Also, some servers refuse to allow
// full hashes in ref specs, so prefer a ref name if known.
refspec = ref + ":" + ref
}
release, err := base.AcquireNet()
if err != nil {
return nil, err
}
// We explicitly set protocol.version=2 for this command to work around
// an apparent Git bug introduced in Git 2.21 (commit 61c771),
// which causes the handler for protocol version 1 to sometimes miss
// tags that point to the requested commit (see https://go.dev/issue/56881).
_, err = Run(ctx, r.dir, "git", "fetch", "-f", "-c", "protocol.version=2", "--depth=1", r.remote, refspec)
release()
if err == nil {
return r.statLocal(ctx, rev, ref)
}
// Don't try to be smart about parsing the error.
// It's too complex and varies too much by git version.
// No matter what went wrong, fall back to a complete fetch.
}
// Last resort.
// Fetch all heads and tags and hope the hash we want is in the history.
if err := r.fetchRefsLocked(ctx); err != nil {
return nil, err
}
return r.statLocal(ctx, rev, rev)
}
// fetchRefsLocked fetches all heads and tags from the origin, along with the
// ancestors of those commits.
//
// We only fetch heads and tags, not arbitrary other commits: we don't want to
// pull in off-branch commits (such as rejected GitHub pull requests) that the
// server may be willing to provide. (See the comments within the stat method
// for more detail.)
//
// fetchRefsLocked requires that r.mu remain locked for the duration of the call.
func (r *gitRepo) fetchRefsLocked(ctx context.Context) error {
if r.fetchLevel < fetchAll {
// NOTE: To work around a bug affecting Git clients up to at least 2.23.0
// (2019-08-16), we must first expand the set of local refs, and only then
// unshallow the repository as a separate fetch operation. (See
// golang.org/issue/34266 and
// https://github.com/git/git/blob/4c86140027f4a0d2caaa3ab4bd8bfc5ce3c11c8a/transport.c#L1303-L1309.)
release, err := base.AcquireNet()
if err != nil {
return err
}
defer release()
if _, err := Run(ctx, r.dir, "git", "fetch", "-f", r.remote, "refs/heads/*:refs/heads/*", "refs/tags/*:refs/tags/*"); err != nil {
return err
}
if _, err := os.Stat(filepath.Join(r.dir, "shallow")); err == nil {
if _, err := Run(ctx, r.dir, "git", "fetch", "--unshallow", "-f", r.remote); err != nil {
return err
}
}
r.fetchLevel = fetchAll
}
return nil
}
// statLocal returns a new RevInfo describing rev in the local git repository.
// It uses version as info.Version.
func (r *gitRepo) statLocal(ctx context.Context, version, rev string) (*RevInfo, error) {
out, err := Run(ctx, r.dir, "git", "-c", "log.showsignature=false", "log", "--no-decorate", "-n1", "--format=format:%H %ct %D", rev, "--")
if err != nil {
// Return info with Origin.RepoSum if possible to allow caching of negative lookup.
var info *RevInfo
if refs, err := r.loadRefs(ctx); err == nil {
info = r.unknownRevisionInfo(refs)
}
return info, &UnknownRevisionError{Rev: rev}
}
f := strings.Fields(string(out))
if len(f) < 2 {
return nil, fmt.Errorf("unexpected response from git log: %q", out)
}
hash := f[0]
if strings.HasPrefix(hash, version) {
version = hash // extend to full hash
}
t, err := strconv.ParseInt(f[1], 10, 64)
if err != nil {
return nil, fmt.Errorf("invalid time from git log: %q", out)
}
info := &RevInfo{
Origin: &Origin{
VCS: "git",
URL: r.remoteURL,
Hash: hash,
},
Name: hash,
Short: ShortenSHA1(hash),
Time: time.Unix(t, 0).UTC(),
Version: hash,
}
if !strings.HasPrefix(hash, rev) {
info.Origin.Ref = rev
}
// Add tags. Output looks like:
// ede458df7cd0fdca520df19a33158086a8a68e81 1523994202 HEAD -> master, tag: v1.2.4-annotated, tag: v1.2.3, origin/master, origin/HEAD
for i := 2; i < len(f); i++ {
if f[i] == "tag:" {
i++
if i < len(f) {
info.Tags = append(info.Tags, strings.TrimSuffix(f[i], ","))
}
}
}
sort.Strings(info.Tags)
// Used hash as info.Version above.
// Use caller's suggested version if it appears in the tag list
// (filters out branch names, HEAD).
for _, tag := range info.Tags {
if version == tag {
info.Version = version
}
}
return info, nil
}
func (r *gitRepo) Stat(ctx context.Context, rev string) (*RevInfo, error) {
if rev == "latest" {
return r.Latest(ctx)
}
return r.statCache.Do(rev, func() (*RevInfo, error) {
return r.stat(ctx, rev)
})
}
func (r *gitRepo) ReadFile(ctx context.Context, rev, file string, maxSize int64) ([]byte, error) {
// TODO: Could use git cat-file --batch.
info, err := r.Stat(ctx, rev) // download rev into local git repo
if err != nil {
return nil, err
}
out, err := Run(ctx, r.dir, "git", "cat-file", "blob", info.Name+":"+file)
if err != nil {
return nil, fs.ErrNotExist
}
return out, nil
}
func (r *gitRepo) RecentTag(ctx context.Context, rev, prefix string, allowed func(tag string) bool) (tag string, err error) {
info, err := r.Stat(ctx, rev)
if err != nil {
return "", err
}
rev = info.Name // expand hash prefixes
// describe sets tag and err using 'git for-each-ref' and reports whether the
// result is definitive.
describe := func() (definitive bool) {
var out []byte
out, err = Run(ctx, r.dir, "git", "for-each-ref", "--format", "%(refname)", "refs/tags", "--merged", rev)
if err != nil {
return true
}
// prefixed tags aren't valid semver tags so compare without prefix, but only tags with correct prefix
var highest string
for _, line := range strings.Split(string(out), "\n") {
line = strings.TrimSpace(line)
// git do support lstrip in for-each-ref format, but it was added in v2.13.0. Stripping here
// instead gives support for git v2.7.0.
if !strings.HasPrefix(line, "refs/tags/") {
continue
}
line = line[len("refs/tags/"):]
if !strings.HasPrefix(line, prefix) {
continue
}
if !allowed(line) {
continue
}
semtag := line[len(prefix):]
if semver.Compare(semtag, highest) > 0 {
highest = semtag
}
}
if highest != "" {
tag = prefix + highest
}
return tag != "" && !AllHex(tag)
}
if describe() {
return tag, err
}
// Git didn't find a version tag preceding the requested rev.
// See whether any plausible tag exists.
tags, err := r.Tags(ctx, prefix+"v")
if err != nil {
return "", err
}
if len(tags.List) == 0 {
return "", nil
}
// There are plausible tags, but we don't know if rev is a descendent of any of them.
// Fetch the history to find out.
unlock, err := r.mu.Lock()
if err != nil {
return "", err
}
defer unlock()
if err := r.fetchRefsLocked(ctx); err != nil {
return "", err
}
// If we've reached this point, we have all of the commits that are reachable
// from all heads and tags.
//
// The only refs we should be missing are those that are no longer reachable
// (or never were reachable) from any branch or tag, including the master
// branch, and we don't want to resolve them anyway (they're probably
// unreachable for a reason).
//
// Try one last time in case some other goroutine fetched rev while we were
// waiting on the lock.
describe()
return tag, err
}
func (r *gitRepo) DescendsFrom(ctx context.Context, rev, tag string) (bool, error) {
// The "--is-ancestor" flag was added to "git merge-base" in version 1.8.0, so
// this won't work with Git 1.7.1. According to golang.org/issue/28550, cmd/go
// already doesn't work with Git 1.7.1, so at least it's not a regression.
//
// git merge-base --is-ancestor exits with status 0 if rev is an ancestor, or
// 1 if not.
_, err := Run(ctx, r.dir, "git", "merge-base", "--is-ancestor", "--", tag, rev)
// Git reports "is an ancestor" with exit code 0 and "not an ancestor" with
// exit code 1.
// Unfortunately, if we've already fetched rev with a shallow history, git
// merge-base has been observed to report a false-negative, so don't stop yet
// even if the exit code is 1!
if err == nil {
return true, nil
}
// See whether the tag and rev even exist.
tags, err := r.Tags(ctx, tag)
if err != nil {
return false, err
}
if len(tags.List) == 0 {
return false, nil
}
// NOTE: r.stat is very careful not to fetch commits that we shouldn't know
// about, like rejected GitHub pull requests, so don't try to short-circuit
// that here.
if _, err = r.stat(ctx, rev); err != nil {
return false, err
}
// Now fetch history so that git can search for a path.
unlock, err := r.mu.Lock()
if err != nil {
return false, err
}
defer unlock()
if r.fetchLevel < fetchAll {
// Fetch the complete history for all refs and heads. It would be more
// efficient to only fetch the history from rev to tag, but that's much more
// complicated, and any kind of shallow fetch is fairly likely to trigger
// bugs in JGit servers and/or the go command anyway.
if err := r.fetchRefsLocked(ctx); err != nil {
return false, err
}
}
_, err = Run(ctx, r.dir, "git", "merge-base", "--is-ancestor", "--", tag, rev)
if err == nil {
return true, nil
}
if ee, ok := err.(*RunError).Err.(*exec.ExitError); ok && ee.ExitCode() == 1 {
return false, nil
}
return false, err
}
func (r *gitRepo) ReadZip(ctx context.Context, rev, subdir string, maxSize int64) (zip io.ReadCloser, err error) {
// TODO: Use maxSize or drop it.
args := []string{}
if subdir != "" {
args = append(args, "--", subdir)
}
info, err := r.Stat(ctx, rev) // download rev into local git repo
if err != nil {
return nil, err
}
unlock, err := r.mu.Lock()
if err != nil {
return nil, err
}
defer unlock()
if err := ensureGitAttributes(r.dir); err != nil {
return nil, err
}
// Incredibly, git produces different archives depending on whether
// it is running on a Windows system or not, in an attempt to normalize
// text file line endings. Setting -c core.autocrlf=input means only
// translate files on the way into the repo, not on the way out (archive).
// The -c core.eol=lf should be unnecessary but set it anyway.
archive, err := Run(ctx, r.dir, "git", "-c", "core.autocrlf=input", "-c", "core.eol=lf", "archive", "--format=zip", "--prefix=prefix/", info.Name, args)
if err != nil {
if bytes.Contains(err.(*RunError).Stderr, []byte("did not match any files")) {
return nil, fs.ErrNotExist
}
return nil, err
}
return io.NopCloser(bytes.NewReader(archive)), nil
}
// ensureGitAttributes makes sure export-subst and export-ignore features are
// disabled for this repo. This is intended to be run prior to running git
// archive so that zip files are generated that produce consistent ziphashes
// for a given revision, independent of variables such as git version and the
// size of the repo.
//
// See: https://github.com/golang/go/issues/27153
func ensureGitAttributes(repoDir string) (err error) {
const attr = "\n* -export-subst -export-ignore\n"
d := repoDir + "/info"
p := d + "/attributes"
if err := os.MkdirAll(d, 0755); err != nil {
return err
}
f, err := os.OpenFile(p, os.O_CREATE|os.O_APPEND|os.O_RDWR, 0666)
if err != nil {
return err
}
defer func() {
closeErr := f.Close()
if closeErr != nil {
err = closeErr
}
}()
b, err := io.ReadAll(f)
if err != nil {
return err
}
if !bytes.HasSuffix(b, []byte(attr)) {
_, err := f.WriteString(attr)
return err
}
return nil
}