1 files changed, 315 insertions, 0 deletions
diff --git a/src/cmd/go/internal/modfetch/codehost/codehost.go b/src/cmd/go/internal/modfetch/codehost/codehost.go
new file mode 100644
index 0000000..378fbae
--- /dev/null
+++ b/src/cmd/go/internal/modfetch/codehost/codehost.go
@@ -0,0 +1,315 @@
+// 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 defines the interface implemented by a code hosting source,
+// along with support code for use by implementations.
+package codehost
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"fmt"
+	exec "internal/execabs"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+
+	"cmd/go/internal/cfg"
+	"cmd/go/internal/lockedfile"
+	"cmd/go/internal/str"
+)
+
+// Downloaded size limits.
+const (
+	MaxGoMod   = 16 << 20  // maximum size of go.mod file
+	MaxLICENSE = 16 << 20  // maximum size of LICENSE file
+	MaxZipFile = 500 << 20 // maximum size of downloaded zip file
+)
+
+// A Repo represents a code hosting source.
+// Typical implementations include local version control repositories,
+// remote version control servers, and code hosting sites.
+// A Repo must be safe for simultaneous use by multiple goroutines.
+type Repo interface {
+	// List lists all tags with the given prefix.
+	Tags(prefix string) (tags []string, err error)
+
+	// Stat returns information about the revision rev.
+	// A revision can be any identifier known to the underlying service:
+	// commit hash, branch, tag, and so on.
+	Stat(rev string) (*RevInfo, error)
+
+	// Latest returns the latest revision on the default branch,
+	// whatever that means in the underlying implementation.
+	Latest() (*RevInfo, error)
+
+	// ReadFile reads the given file in the file tree corresponding to revision rev.
+	// It should refuse to read more than maxSize bytes.
+	//
+	// If the requested file does not exist it should return an error for which
+	// os.IsNotExist(err) returns true.
+	ReadFile(rev, file string, maxSize int64) (data []byte, err error)
+
+	// ReadFileRevs reads a single file at multiple versions.
+	// It should refuse to read more than maxSize bytes.
+	// The result is a map from each requested rev strings
+	// to the associated FileRev. The map must have a non-nil
+	// entry for every requested rev (unless ReadFileRevs returned an error).
+	// A file simply being missing or even corrupted in revs[i]
+	// should be reported only in files[revs[i]].Err, not in the error result
+	// from ReadFileRevs.
+	// The overall call should return an error (and no map) only
+	// in the case of a problem with obtaining the data, such as
+	// a network failure.
+	// Implementations may assume that revs only contain tags,
+	// not direct commit hashes.
+	ReadFileRevs(revs []string, file string, maxSize int64) (files map[string]*FileRev, err error)
+
+	// ReadZip downloads a zip file for the subdir subdirectory
+	// of the given revision to a new file in a given temporary directory.
+	// It should refuse to read more than maxSize bytes.
+	// It returns a ReadCloser for a streamed copy of the zip file.
+	// All files in the zip file are expected to be
+	// nested in a single top-level directory, whose name is not specified.
+	ReadZip(rev, subdir string, maxSize int64) (zip io.ReadCloser, err error)
+
+	// RecentTag returns the most recent tag on rev or one of its predecessors
+	// with the given prefix. allowed may be used to filter out unwanted versions.
+	RecentTag(rev, prefix string, allowed func(string) bool) (tag string, err error)
+
+	// DescendsFrom reports whether rev or any of its ancestors has the given tag.
+	//
+	// DescendsFrom must return true for any tag returned by RecentTag for the
+	// same revision.
+	DescendsFrom(rev, tag string) (bool, error)
+}
+
+// A Rev describes a single revision in a source code repository.
+type RevInfo struct {
+	Name    string    // complete ID in underlying repository
+	Short   string    // shortened ID, for use in pseudo-version
+	Version string    // version used in lookup
+	Time    time.Time // commit time
+	Tags    []string  // known tags for commit
+}
+
+// A FileRev describes the result of reading a file at a given revision.
+type FileRev struct {
+	Rev  string // requested revision
+	Data []byte // file data
+	Err  error  // error if any; os.IsNotExist(Err)==true if rev exists but file does not exist in that rev
+}
+
+// UnknownRevisionError is an error equivalent to fs.ErrNotExist, but for a
+// revision rather than a file.
+type UnknownRevisionError struct {
+	Rev string
+}
+
+func (e *UnknownRevisionError) Error() string {
+	return "unknown revision " + e.Rev
+}
+func (UnknownRevisionError) Is(err error) bool {
+	return err == fs.ErrNotExist
+}
+
+// ErrNoCommits is an error equivalent to fs.ErrNotExist indicating that a given
+// repository or module contains no commits.
+var ErrNoCommits error = noCommitsError{}
+
+type noCommitsError struct{}
+
+func (noCommitsError) Error() string {
+	return "no commits"
+}
+func (noCommitsError) Is(err error) bool {
+	return err == fs.ErrNotExist
+}
+
+// AllHex reports whether the revision rev is entirely lower-case hexadecimal digits.
+func AllHex(rev string) bool {
+	for i := 0; i < len(rev); i++ {
+		c := rev[i]
+		if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' {
+			continue
+		}
+		return false
+	}
+	return true
+}
+
+// ShortenSHA1 shortens a SHA1 hash (40 hex digits) to the canonical length
+// used in pseudo-versions (12 hex digits).
+func ShortenSHA1(rev string) string {
+	if AllHex(rev) && len(rev) == 40 {
+		return rev[:12]
+	}
+	return rev
+}
+
+// WorkDir returns the name of the cached work directory to use for the
+// given repository type and name.
+func WorkDir(typ, name string) (dir, lockfile string, err error) {
+	if cfg.GOMODCACHE == "" {
+		return "", "", fmt.Errorf("neither GOPATH nor GOMODCACHE are set")
+	}
+
+	// We name the work directory for the SHA256 hash of the type and name.
+	// We intentionally avoid the actual name both because of possible
+	// conflicts with valid file system paths and because we want to ensure
+	// that one checkout is never nested inside another. That nesting has
+	// led to security problems in the past.
+	if strings.Contains(typ, ":") {
+		return "", "", fmt.Errorf("codehost.WorkDir: type cannot contain colon")
+	}
+	key := typ + ":" + name
+	dir = filepath.Join(cfg.GOMODCACHE, "cache/vcs", fmt.Sprintf("%x", sha256.Sum256([]byte(key))))
+
+	if cfg.BuildX {
+		fmt.Fprintf(os.Stderr, "mkdir -p %s # %s %s\n", filepath.Dir(dir), typ, name)
+	}
+	if err := os.MkdirAll(filepath.Dir(dir), 0777); err != nil {
+		return "", "", err
+	}
+
+	lockfile = dir + ".lock"
+	if cfg.BuildX {
+		fmt.Fprintf(os.Stderr, "# lock %s", lockfile)
+	}
+
+	unlock, err := lockedfile.MutexAt(lockfile).Lock()
+	if err != nil {
+		return "", "", fmt.Errorf("codehost.WorkDir: can't find or create lock file: %v", err)
+	}
+	defer unlock()
+
+	data, err := os.ReadFile(dir + ".info")
+	info, err2 := os.Stat(dir)
+	if err == nil && err2 == nil && info.IsDir() {
+		// Info file and directory both already exist: reuse.
+		have := strings.TrimSuffix(string(data), "\n")
+		if have != key {
+			return "", "", fmt.Errorf("%s exists with wrong content (have %q want %q)", dir+".info", have, key)
+		}
+		if cfg.BuildX {
+			fmt.Fprintf(os.Stderr, "# %s for %s %s\n", dir, typ, name)
+		}
+		return dir, lockfile, nil
+	}
+
+	// Info file or directory missing. Start from scratch.
+	if cfg.BuildX {
+		fmt.Fprintf(os.Stderr, "mkdir -p %s # %s %s\n", dir, typ, name)
+	}
+	os.RemoveAll(dir)
+	if err := os.MkdirAll(dir, 0777); err != nil {
+		return "", "", err
+	}
+	if err := os.WriteFile(dir+".info", []byte(key), 0666); err != nil {
+		os.RemoveAll(dir)
+		return "", "", err
+	}
+	return dir, lockfile, nil
+}
+
+type RunError struct {
+	Cmd      string
+	Err      error
+	Stderr   []byte
+	HelpText string
+}
+
+func (e *RunError) Error() string {
+	text := e.Cmd + ": " + e.Err.Error()
+	stderr := bytes.TrimRight(e.Stderr, "\n")
+	if len(stderr) > 0 {
+		text += ":\n\t" + strings.ReplaceAll(string(stderr), "\n", "\n\t")
+	}
+	if len(e.HelpText) > 0 {
+		text += "\n" + e.HelpText
+	}
+	return text
+}
+
+var dirLock sync.Map
+
+// Run runs the command line in the given directory
+// (an empty dir means the current directory).
+// It returns the standard output and, for a non-zero exit,
+// a *RunError indicating the command, exit status, and standard error.
+// Standard error is unavailable for commands that exit successfully.
+func Run(dir string, cmdline ...interface{}) ([]byte, error) {
+	return RunWithStdin(dir, nil, cmdline...)
+}
+
+// bashQuoter escapes characters that have special meaning in double-quoted strings in the bash shell.
+// See https://www.gnu.org/software/bash/manual/html_node/Double-Quotes.html.
+var bashQuoter = strings.NewReplacer(`"`, `\"`, `$`, `\$`, "`", "\\`", `\`, `\\`)
+
+func RunWithStdin(dir string, stdin io.Reader, cmdline ...interface{}) ([]byte, error) {
+	if dir != "" {
+		muIface, ok := dirLock.Load(dir)
+		if !ok {
+			muIface, _ = dirLock.LoadOrStore(dir, new(sync.Mutex))
+		}
+		mu := muIface.(*sync.Mutex)
+		mu.Lock()
+		defer mu.Unlock()
+	}
+
+	cmd := str.StringList(cmdline...)
+	if os.Getenv("TESTGOVCS") == "panic" {
+		panic(fmt.Sprintf("use of vcs: %v", cmd))
+	}
+	if cfg.BuildX {
+		text := new(strings.Builder)
+		if dir != "" {
+			text.WriteString("cd ")
+			text.WriteString(dir)
+			text.WriteString("; ")
+		}
+		for i, arg := range cmd {
+			if i > 0 {
+				text.WriteByte(' ')
+			}
+			switch {
+			case strings.ContainsAny(arg, "'"):
+				// Quote args that could be mistaken for quoted args.
+				text.WriteByte('"')
+				text.WriteString(bashQuoter.Replace(arg))
+				text.WriteByte('"')
+			case strings.ContainsAny(arg, "$`\\*?[\"\t\n\v\f\r \u0085\u00a0"):
+				// Quote args that contain special characters, glob patterns, or spaces.
+				text.WriteByte('\'')
+				text.WriteString(arg)
+				text.WriteByte('\'')
+			default:
+				text.WriteString(arg)
+			}
+		}
+		fmt.Fprintf(os.Stderr, "%s\n", text)
+		start := time.Now()
+		defer func() {
+			fmt.Fprintf(os.Stderr, "%.3fs # %s\n", time.Since(start).Seconds(), text)
+		}()
+	}
+	// TODO: Impose limits on command output size.
+	// TODO: Set environment to get English error messages.
+	var stderr bytes.Buffer
+	var stdout bytes.Buffer
+	c := exec.Command(cmd[0], cmd[1:]...)
+	c.Dir = dir
+	c.Stdin = stdin
+	c.Stderr = &stderr
+	c.Stdout = &stdout
+	err := c.Run()
+	if err != nil {
+		err = &RunError{Cmd: strings.Join(cmd, " ") + " in " + dir, Stderr: stderr.Bytes(), Err: err}
+	}
+	return stdout.Bytes(), err
+}