Source file src/cmd/go/internal/get/vcs.go

Documentation: cmd/go/internal/get

     1  // Copyright 2012 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package get
     6  
     7  import (
     8  	"encoding/json"
     9  	"errors"
    10  	"fmt"
    11  	"internal/lazyregexp"
    12  	"internal/singleflight"
    13  	"log"
    14  	urlpkg "net/url"
    15  	"os"
    16  	"os/exec"
    17  	"path/filepath"
    18  	"regexp"
    19  	"strings"
    20  	"sync"
    21  
    22  	"cmd/go/internal/base"
    23  	"cmd/go/internal/cfg"
    24  	"cmd/go/internal/web"
    25  )
    26  
    27  // A vcsCmd describes how to use a version control system
    28  // like Mercurial, Git, or Subversion.
    29  type vcsCmd struct {
    30  	name string
    31  	cmd  string // name of binary to invoke command
    32  
    33  	createCmd   []string // commands to download a fresh copy of a repository
    34  	downloadCmd []string // commands to download updates into an existing repository
    35  
    36  	tagCmd         []tagCmd // commands to list tags
    37  	tagLookupCmd   []tagCmd // commands to lookup tags before running tagSyncCmd
    38  	tagSyncCmd     []string // commands to sync to specific tag
    39  	tagSyncDefault []string // commands to sync to default tag
    40  
    41  	scheme  []string
    42  	pingCmd string
    43  
    44  	remoteRepo  func(v *vcsCmd, rootDir string) (remoteRepo string, err error)
    45  	resolveRepo func(v *vcsCmd, rootDir, remoteRepo string) (realRepo string, err error)
    46  }
    47  
    48  var defaultSecureScheme = map[string]bool{
    49  	"https":   true,
    50  	"git+ssh": true,
    51  	"bzr+ssh": true,
    52  	"svn+ssh": true,
    53  	"ssh":     true,
    54  }
    55  
    56  func (v *vcsCmd) isSecure(repo string) bool {
    57  	u, err := urlpkg.Parse(repo)
    58  	if err != nil {
    59  		// If repo is not a URL, it's not secure.
    60  		return false
    61  	}
    62  	return v.isSecureScheme(u.Scheme)
    63  }
    64  
    65  func (v *vcsCmd) isSecureScheme(scheme string) bool {
    66  	switch v.cmd {
    67  	case "git":
    68  		// GIT_ALLOW_PROTOCOL is an environment variable defined by Git. It is a
    69  		// colon-separated list of schemes that are allowed to be used with git
    70  		// fetch/clone. Any scheme not mentioned will be considered insecure.
    71  		if allow := os.Getenv("GIT_ALLOW_PROTOCOL"); allow != "" {
    72  			for _, s := range strings.Split(allow, ":") {
    73  				if s == scheme {
    74  					return true
    75  				}
    76  			}
    77  			return false
    78  		}
    79  	}
    80  	return defaultSecureScheme[scheme]
    81  }
    82  
    83  // A tagCmd describes a command to list available tags
    84  // that can be passed to tagSyncCmd.
    85  type tagCmd struct {
    86  	cmd     string // command to list tags
    87  	pattern string // regexp to extract tags from list
    88  }
    89  
    90  // vcsList lists the known version control systems
    91  var vcsList = []*vcsCmd{
    92  	vcsHg,
    93  	vcsGit,
    94  	vcsSvn,
    95  	vcsBzr,
    96  	vcsFossil,
    97  }
    98  
    99  // vcsByCmd returns the version control system for the given
   100  // command name (hg, git, svn, bzr).
   101  func vcsByCmd(cmd string) *vcsCmd {
   102  	for _, vcs := range vcsList {
   103  		if vcs.cmd == cmd {
   104  			return vcs
   105  		}
   106  	}
   107  	return nil
   108  }
   109  
   110  // vcsHg describes how to use Mercurial.
   111  var vcsHg = &vcsCmd{
   112  	name: "Mercurial",
   113  	cmd:  "hg",
   114  
   115  	createCmd:   []string{"clone -U -- {repo} {dir}"},
   116  	downloadCmd: []string{"pull"},
   117  
   118  	// We allow both tag and branch names as 'tags'
   119  	// for selecting a version. This lets people have
   120  	// a go.release.r60 branch and a go1 branch
   121  	// and make changes in both, without constantly
   122  	// editing .hgtags.
   123  	tagCmd: []tagCmd{
   124  		{"tags", `^(\S+)`},
   125  		{"branches", `^(\S+)`},
   126  	},
   127  	tagSyncCmd:     []string{"update -r {tag}"},
   128  	tagSyncDefault: []string{"update default"},
   129  
   130  	scheme:     []string{"https", "http", "ssh"},
   131  	pingCmd:    "identify -- {scheme}://{repo}",
   132  	remoteRepo: hgRemoteRepo,
   133  }
   134  
   135  func hgRemoteRepo(vcsHg *vcsCmd, rootDir string) (remoteRepo string, err error) {
   136  	out, err := vcsHg.runOutput(rootDir, "paths default")
   137  	if err != nil {
   138  		return "", err
   139  	}
   140  	return strings.TrimSpace(string(out)), nil
   141  }
   142  
   143  // vcsGit describes how to use Git.
   144  var vcsGit = &vcsCmd{
   145  	name: "Git",
   146  	cmd:  "git",
   147  
   148  	createCmd:   []string{"clone -- {repo} {dir}", "-go-internal-cd {dir} submodule update --init --recursive"},
   149  	downloadCmd: []string{"pull --ff-only", "submodule update --init --recursive"},
   150  
   151  	tagCmd: []tagCmd{
   152  		// tags/xxx matches a git tag named xxx
   153  		// origin/xxx matches a git branch named xxx on the default remote repository
   154  		{"show-ref", `(?:tags|origin)/(\S+)$`},
   155  	},
   156  	tagLookupCmd: []tagCmd{
   157  		{"show-ref tags/{tag} origin/{tag}", `((?:tags|origin)/\S+)$`},
   158  	},
   159  	tagSyncCmd: []string{"checkout {tag}", "submodule update --init --recursive"},
   160  	// both createCmd and downloadCmd update the working dir.
   161  	// No need to do more here. We used to 'checkout master'
   162  	// but that doesn't work if the default branch is not named master.
   163  	// DO NOT add 'checkout master' here.
   164  	// See golang.org/issue/9032.
   165  	tagSyncDefault: []string{"submodule update --init --recursive"},
   166  
   167  	scheme: []string{"git", "https", "http", "git+ssh", "ssh"},
   168  
   169  	// Leave out the '--' separator in the ls-remote command: git 2.7.4 does not
   170  	// support such a separator for that command, and this use should be safe
   171  	// without it because the {scheme} value comes from the predefined list above.
   172  	// See golang.org/issue/33836.
   173  	pingCmd: "ls-remote {scheme}://{repo}",
   174  
   175  	remoteRepo: gitRemoteRepo,
   176  }
   177  
   178  // scpSyntaxRe matches the SCP-like addresses used by Git to access
   179  // repositories by SSH.
   180  var scpSyntaxRe = lazyregexp.New(`^([a-zA-Z0-9_]+)@([a-zA-Z0-9._-]+):(.*)$`)
   181  
   182  func gitRemoteRepo(vcsGit *vcsCmd, rootDir string) (remoteRepo string, err error) {
   183  	cmd := "config remote.origin.url"
   184  	errParse := errors.New("unable to parse output of git " + cmd)
   185  	errRemoteOriginNotFound := errors.New("remote origin not found")
   186  	outb, err := vcsGit.run1(rootDir, cmd, nil, false)
   187  	if err != nil {
   188  		// if it doesn't output any message, it means the config argument is correct,
   189  		// but the config value itself doesn't exist
   190  		if outb != nil && len(outb) == 0 {
   191  			return "", errRemoteOriginNotFound
   192  		}
   193  		return "", err
   194  	}
   195  	out := strings.TrimSpace(string(outb))
   196  
   197  	var repoURL *urlpkg.URL
   198  	if m := scpSyntaxRe.FindStringSubmatch(out); m != nil {
   199  		// Match SCP-like syntax and convert it to a URL.
   200  		// Eg, "git@github.com:user/repo" becomes
   201  		// "ssh://git@github.com/user/repo".
   202  		repoURL = &urlpkg.URL{
   203  			Scheme: "ssh",
   204  			User:   urlpkg.User(m[1]),
   205  			Host:   m[2],
   206  			Path:   m[3],
   207  		}
   208  	} else {
   209  		repoURL, err = urlpkg.Parse(out)
   210  		if err != nil {
   211  			return "", err
   212  		}
   213  	}
   214  
   215  	// Iterate over insecure schemes too, because this function simply
   216  	// reports the state of the repo. If we can't see insecure schemes then
   217  	// we can't report the actual repo URL.
   218  	for _, s := range vcsGit.scheme {
   219  		if repoURL.Scheme == s {
   220  			return repoURL.String(), nil
   221  		}
   222  	}
   223  	return "", errParse
   224  }
   225  
   226  // vcsBzr describes how to use Bazaar.
   227  var vcsBzr = &vcsCmd{
   228  	name: "Bazaar",
   229  	cmd:  "bzr",
   230  
   231  	createCmd: []string{"branch -- {repo} {dir}"},
   232  
   233  	// Without --overwrite bzr will not pull tags that changed.
   234  	// Replace by --overwrite-tags after http://pad.lv/681792 goes in.
   235  	downloadCmd: []string{"pull --overwrite"},
   236  
   237  	tagCmd:         []tagCmd{{"tags", `^(\S+)`}},
   238  	tagSyncCmd:     []string{"update -r {tag}"},
   239  	tagSyncDefault: []string{"update -r revno:-1"},
   240  
   241  	scheme:      []string{"https", "http", "bzr", "bzr+ssh"},
   242  	pingCmd:     "info -- {scheme}://{repo}",
   243  	remoteRepo:  bzrRemoteRepo,
   244  	resolveRepo: bzrResolveRepo,
   245  }
   246  
   247  func bzrRemoteRepo(vcsBzr *vcsCmd, rootDir string) (remoteRepo string, err error) {
   248  	outb, err := vcsBzr.runOutput(rootDir, "config parent_location")
   249  	if err != nil {
   250  		return "", err
   251  	}
   252  	return strings.TrimSpace(string(outb)), nil
   253  }
   254  
   255  func bzrResolveRepo(vcsBzr *vcsCmd, rootDir, remoteRepo string) (realRepo string, err error) {
   256  	outb, err := vcsBzr.runOutput(rootDir, "info "+remoteRepo)
   257  	if err != nil {
   258  		return "", err
   259  	}
   260  	out := string(outb)
   261  
   262  	// Expect:
   263  	// ...
   264  	//   (branch root|repository branch): <URL>
   265  	// ...
   266  
   267  	found := false
   268  	for _, prefix := range []string{"\n  branch root: ", "\n  repository branch: "} {
   269  		i := strings.Index(out, prefix)
   270  		if i >= 0 {
   271  			out = out[i+len(prefix):]
   272  			found = true
   273  			break
   274  		}
   275  	}
   276  	if !found {
   277  		return "", fmt.Errorf("unable to parse output of bzr info")
   278  	}
   279  
   280  	i := strings.Index(out, "\n")
   281  	if i < 0 {
   282  		return "", fmt.Errorf("unable to parse output of bzr info")
   283  	}
   284  	out = out[:i]
   285  	return strings.TrimSpace(out), nil
   286  }
   287  
   288  // vcsSvn describes how to use Subversion.
   289  var vcsSvn = &vcsCmd{
   290  	name: "Subversion",
   291  	cmd:  "svn",
   292  
   293  	createCmd:   []string{"checkout -- {repo} {dir}"},
   294  	downloadCmd: []string{"update"},
   295  
   296  	// There is no tag command in subversion.
   297  	// The branch information is all in the path names.
   298  
   299  	scheme:     []string{"https", "http", "svn", "svn+ssh"},
   300  	pingCmd:    "info -- {scheme}://{repo}",
   301  	remoteRepo: svnRemoteRepo,
   302  }
   303  
   304  func svnRemoteRepo(vcsSvn *vcsCmd, rootDir string) (remoteRepo string, err error) {
   305  	outb, err := vcsSvn.runOutput(rootDir, "info")
   306  	if err != nil {
   307  		return "", err
   308  	}
   309  	out := string(outb)
   310  
   311  	// Expect:
   312  	//
   313  	//	 ...
   314  	// 	URL: <URL>
   315  	// 	...
   316  	//
   317  	// Note that we're not using the Repository Root line,
   318  	// because svn allows checking out subtrees.
   319  	// The URL will be the URL of the subtree (what we used with 'svn co')
   320  	// while the Repository Root may be a much higher parent.
   321  	i := strings.Index(out, "\nURL: ")
   322  	if i < 0 {
   323  		return "", fmt.Errorf("unable to parse output of svn info")
   324  	}
   325  	out = out[i+len("\nURL: "):]
   326  	i = strings.Index(out, "\n")
   327  	if i < 0 {
   328  		return "", fmt.Errorf("unable to parse output of svn info")
   329  	}
   330  	out = out[:i]
   331  	return strings.TrimSpace(out), nil
   332  }
   333  
   334  // fossilRepoName is the name go get associates with a fossil repository. In the
   335  // real world the file can be named anything.
   336  const fossilRepoName = ".fossil"
   337  
   338  // vcsFossil describes how to use Fossil (fossil-scm.org)
   339  var vcsFossil = &vcsCmd{
   340  	name: "Fossil",
   341  	cmd:  "fossil",
   342  
   343  	createCmd:   []string{"-go-internal-mkdir {dir} clone -- {repo} " + filepath.Join("{dir}", fossilRepoName), "-go-internal-cd {dir} open .fossil"},
   344  	downloadCmd: []string{"up"},
   345  
   346  	tagCmd:         []tagCmd{{"tag ls", `(.*)`}},
   347  	tagSyncCmd:     []string{"up tag:{tag}"},
   348  	tagSyncDefault: []string{"up trunk"},
   349  
   350  	scheme:     []string{"https", "http"},
   351  	remoteRepo: fossilRemoteRepo,
   352  }
   353  
   354  func fossilRemoteRepo(vcsFossil *vcsCmd, rootDir string) (remoteRepo string, err error) {
   355  	out, err := vcsFossil.runOutput(rootDir, "remote-url")
   356  	if err != nil {
   357  		return "", err
   358  	}
   359  	return strings.TrimSpace(string(out)), nil
   360  }
   361  
   362  func (v *vcsCmd) String() string {
   363  	return v.name
   364  }
   365  
   366  // run runs the command line cmd in the given directory.
   367  // keyval is a list of key, value pairs. run expands
   368  // instances of {key} in cmd into value, but only after
   369  // splitting cmd into individual arguments.
   370  // If an error occurs, run prints the command line and the
   371  // command's combined stdout+stderr to standard error.
   372  // Otherwise run discards the command's output.
   373  func (v *vcsCmd) run(dir string, cmd string, keyval ...string) error {
   374  	_, err := v.run1(dir, cmd, keyval, true)
   375  	return err
   376  }
   377  
   378  // runVerboseOnly is like run but only generates error output to standard error in verbose mode.
   379  func (v *vcsCmd) runVerboseOnly(dir string, cmd string, keyval ...string) error {
   380  	_, err := v.run1(dir, cmd, keyval, false)
   381  	return err
   382  }
   383  
   384  // runOutput is like run but returns the output of the command.
   385  func (v *vcsCmd) runOutput(dir string, cmd string, keyval ...string) ([]byte, error) {
   386  	return v.run1(dir, cmd, keyval, true)
   387  }
   388  
   389  // run1 is the generalized implementation of run and runOutput.
   390  func (v *vcsCmd) run1(dir string, cmdline string, keyval []string, verbose bool) ([]byte, error) {
   391  	m := make(map[string]string)
   392  	for i := 0; i < len(keyval); i += 2 {
   393  		m[keyval[i]] = keyval[i+1]
   394  	}
   395  	args := strings.Fields(cmdline)
   396  	for i, arg := range args {
   397  		args[i] = expand(m, arg)
   398  	}
   399  
   400  	if len(args) >= 2 && args[0] == "-go-internal-mkdir" {
   401  		var err error
   402  		if filepath.IsAbs(args[1]) {
   403  			err = os.Mkdir(args[1], os.ModePerm)
   404  		} else {
   405  			err = os.Mkdir(filepath.Join(dir, args[1]), os.ModePerm)
   406  		}
   407  		if err != nil {
   408  			return nil, err
   409  		}
   410  		args = args[2:]
   411  	}
   412  
   413  	if len(args) >= 2 && args[0] == "-go-internal-cd" {
   414  		if filepath.IsAbs(args[1]) {
   415  			dir = args[1]
   416  		} else {
   417  			dir = filepath.Join(dir, args[1])
   418  		}
   419  		args = args[2:]
   420  	}
   421  
   422  	_, err := exec.LookPath(v.cmd)
   423  	if err != nil {
   424  		fmt.Fprintf(os.Stderr,
   425  			"go: missing %s command. See https://golang.org/s/gogetcmd\n",
   426  			v.name)
   427  		return nil, err
   428  	}
   429  
   430  	cmd := exec.Command(v.cmd, args...)
   431  	cmd.Dir = dir
   432  	cmd.Env = base.EnvForDir(cmd.Dir, os.Environ())
   433  	if cfg.BuildX {
   434  		fmt.Fprintf(os.Stderr, "cd %s\n", dir)
   435  		fmt.Fprintf(os.Stderr, "%s %s\n", v.cmd, strings.Join(args, " "))
   436  	}
   437  	out, err := cmd.Output()
   438  	if err != nil {
   439  		if verbose || cfg.BuildV {
   440  			fmt.Fprintf(os.Stderr, "# cd %s; %s %s\n", dir, v.cmd, strings.Join(args, " "))
   441  			if ee, ok := err.(*exec.ExitError); ok && len(ee.Stderr) > 0 {
   442  				os.Stderr.Write(ee.Stderr)
   443  			} else {
   444  				fmt.Fprintf(os.Stderr, err.Error())
   445  			}
   446  		}
   447  	}
   448  	return out, err
   449  }
   450  
   451  // ping pings to determine scheme to use.
   452  func (v *vcsCmd) ping(scheme, repo string) error {
   453  	return v.runVerboseOnly(".", v.pingCmd, "scheme", scheme, "repo", repo)
   454  }
   455  
   456  // create creates a new copy of repo in dir.
   457  // The parent of dir must exist; dir must not.
   458  func (v *vcsCmd) create(dir, repo string) error {
   459  	for _, cmd := range v.createCmd {
   460  		if err := v.run(".", cmd, "dir", dir, "repo", repo); err != nil {
   461  			return err
   462  		}
   463  	}
   464  	return nil
   465  }
   466  
   467  // download downloads any new changes for the repo in dir.
   468  func (v *vcsCmd) download(dir string) error {
   469  	for _, cmd := range v.downloadCmd {
   470  		if err := v.run(dir, cmd); err != nil {
   471  			return err
   472  		}
   473  	}
   474  	return nil
   475  }
   476  
   477  // tags returns the list of available tags for the repo in dir.
   478  func (v *vcsCmd) tags(dir string) ([]string, error) {
   479  	var tags []string
   480  	for _, tc := range v.tagCmd {
   481  		out, err := v.runOutput(dir, tc.cmd)
   482  		if err != nil {
   483  			return nil, err
   484  		}
   485  		re := regexp.MustCompile(`(?m-s)` + tc.pattern)
   486  		for _, m := range re.FindAllStringSubmatch(string(out), -1) {
   487  			tags = append(tags, m[1])
   488  		}
   489  	}
   490  	return tags, nil
   491  }
   492  
   493  // tagSync syncs the repo in dir to the named tag,
   494  // which either is a tag returned by tags or is v.tagDefault.
   495  func (v *vcsCmd) tagSync(dir, tag string) error {
   496  	if v.tagSyncCmd == nil {
   497  		return nil
   498  	}
   499  	if tag != "" {
   500  		for _, tc := range v.tagLookupCmd {
   501  			out, err := v.runOutput(dir, tc.cmd, "tag", tag)
   502  			if err != nil {
   503  				return err
   504  			}
   505  			re := regexp.MustCompile(`(?m-s)` + tc.pattern)
   506  			m := re.FindStringSubmatch(string(out))
   507  			if len(m) > 1 {
   508  				tag = m[1]
   509  				break
   510  			}
   511  		}
   512  	}
   513  
   514  	if tag == "" && v.tagSyncDefault != nil {
   515  		for _, cmd := range v.tagSyncDefault {
   516  			if err := v.run(dir, cmd); err != nil {
   517  				return err
   518  			}
   519  		}
   520  		return nil
   521  	}
   522  
   523  	for _, cmd := range v.tagSyncCmd {
   524  		if err := v.run(dir, cmd, "tag", tag); err != nil {
   525  			return err
   526  		}
   527  	}
   528  	return nil
   529  }
   530  
   531  // A vcsPath describes how to convert an import path into a
   532  // version control system and repository name.
   533  type vcsPath struct {
   534  	prefix string                              // prefix this description applies to
   535  	regexp *lazyregexp.Regexp                  // compiled pattern for import path
   536  	repo   string                              // repository to use (expand with match of re)
   537  	vcs    string                              // version control system to use (expand with match of re)
   538  	check  func(match map[string]string) error // additional checks
   539  	ping   bool                                // ping for scheme to use to download repo
   540  }
   541  
   542  // vcsFromDir inspects dir and its parents to determine the
   543  // version control system and code repository to use.
   544  // On return, root is the import path
   545  // corresponding to the root of the repository.
   546  func vcsFromDir(dir, srcRoot string) (vcs *vcsCmd, root string, err error) {
   547  	// Clean and double-check that dir is in (a subdirectory of) srcRoot.
   548  	dir = filepath.Clean(dir)
   549  	srcRoot = filepath.Clean(srcRoot)
   550  	if len(dir) <= len(srcRoot) || dir[len(srcRoot)] != filepath.Separator {
   551  		return nil, "", fmt.Errorf("directory %q is outside source root %q", dir, srcRoot)
   552  	}
   553  
   554  	var vcsRet *vcsCmd
   555  	var rootRet string
   556  
   557  	origDir := dir
   558  	for len(dir) > len(srcRoot) {
   559  		for _, vcs := range vcsList {
   560  			if _, err := os.Stat(filepath.Join(dir, "."+vcs.cmd)); err == nil {
   561  				root := filepath.ToSlash(dir[len(srcRoot)+1:])
   562  				// Record first VCS we find, but keep looking,
   563  				// to detect mistakes like one kind of VCS inside another.
   564  				if vcsRet == nil {
   565  					vcsRet = vcs
   566  					rootRet = root
   567  					continue
   568  				}
   569  				// Allow .git inside .git, which can arise due to submodules.
   570  				if vcsRet == vcs && vcs.cmd == "git" {
   571  					continue
   572  				}
   573  				// Otherwise, we have one VCS inside a different VCS.
   574  				return nil, "", fmt.Errorf("directory %q uses %s, but parent %q uses %s",
   575  					filepath.Join(srcRoot, rootRet), vcsRet.cmd, filepath.Join(srcRoot, root), vcs.cmd)
   576  			}
   577  		}
   578  
   579  		// Move to parent.
   580  		ndir := filepath.Dir(dir)
   581  		if len(ndir) >= len(dir) {
   582  			// Shouldn't happen, but just in case, stop.
   583  			break
   584  		}
   585  		dir = ndir
   586  	}
   587  
   588  	if vcsRet != nil {
   589  		return vcsRet, rootRet, nil
   590  	}
   591  
   592  	return nil, "", fmt.Errorf("directory %q is not using a known version control system", origDir)
   593  }
   594  
   595  // checkNestedVCS checks for an incorrectly-nested VCS-inside-VCS
   596  // situation for dir, checking parents up until srcRoot.
   597  func checkNestedVCS(vcs *vcsCmd, dir, srcRoot string) error {
   598  	if len(dir) <= len(srcRoot) || dir[len(srcRoot)] != filepath.Separator {
   599  		return fmt.Errorf("directory %q is outside source root %q", dir, srcRoot)
   600  	}
   601  
   602  	otherDir := dir
   603  	for len(otherDir) > len(srcRoot) {
   604  		for _, otherVCS := range vcsList {
   605  			if _, err := os.Stat(filepath.Join(otherDir, "."+otherVCS.cmd)); err == nil {
   606  				// Allow expected vcs in original dir.
   607  				if otherDir == dir && otherVCS == vcs {
   608  					continue
   609  				}
   610  				// Allow .git inside .git, which can arise due to submodules.
   611  				if otherVCS == vcs && vcs.cmd == "git" {
   612  					continue
   613  				}
   614  				// Otherwise, we have one VCS inside a different VCS.
   615  				return fmt.Errorf("directory %q uses %s, but parent %q uses %s", dir, vcs.cmd, otherDir, otherVCS.cmd)
   616  			}
   617  		}
   618  		// Move to parent.
   619  		newDir := filepath.Dir(otherDir)
   620  		if len(newDir) >= len(otherDir) {
   621  			// Shouldn't happen, but just in case, stop.
   622  			break
   623  		}
   624  		otherDir = newDir
   625  	}
   626  
   627  	return nil
   628  }
   629  
   630  // RepoRoot describes the repository root for a tree of source code.
   631  type RepoRoot struct {
   632  	Repo     string // repository URL, including scheme
   633  	Root     string // import path corresponding to root of repo
   634  	IsCustom bool   // defined by served <meta> tags (as opposed to hard-coded pattern)
   635  	VCS      string // vcs type ("mod", "git", ...)
   636  
   637  	vcs *vcsCmd // internal: vcs command access
   638  }
   639  
   640  func httpPrefix(s string) string {
   641  	for _, prefix := range [...]string{"http:", "https:"} {
   642  		if strings.HasPrefix(s, prefix) {
   643  			return prefix
   644  		}
   645  	}
   646  	return ""
   647  }
   648  
   649  // ModuleMode specifies whether to prefer modules when looking up code sources.
   650  type ModuleMode int
   651  
   652  const (
   653  	IgnoreMod ModuleMode = iota
   654  	PreferMod
   655  )
   656  
   657  // RepoRootForImportPath analyzes importPath to determine the
   658  // version control system, and code repository to use.
   659  func RepoRootForImportPath(importPath string, mod ModuleMode, security web.SecurityMode) (*RepoRoot, error) {
   660  	rr, err := repoRootFromVCSPaths(importPath, "", security, vcsPaths)
   661  	if err == errUnknownSite {
   662  		rr, err = repoRootForImportDynamic(importPath, mod, security)
   663  		if err != nil {
   664  			err = fmt.Errorf("unrecognized import path %q (%v)", importPath, err)
   665  		}
   666  	}
   667  	if err != nil {
   668  		rr1, err1 := repoRootFromVCSPaths(importPath, "", security, vcsPathsAfterDynamic)
   669  		if err1 == nil {
   670  			rr = rr1
   671  			err = nil
   672  		}
   673  	}
   674  
   675  	// Should have been taken care of above, but make sure.
   676  	if err == nil && strings.Contains(importPath, "...") && strings.Contains(rr.Root, "...") {
   677  		// Do not allow wildcards in the repo root.
   678  		rr = nil
   679  		err = fmt.Errorf("cannot expand ... in %q", importPath)
   680  	}
   681  	return rr, err
   682  }
   683  
   684  var errUnknownSite = errors.New("dynamic lookup required to find mapping")
   685  
   686  // repoRootFromVCSPaths attempts to map importPath to a repoRoot
   687  // using the mappings defined in vcsPaths.
   688  // If scheme is non-empty, that scheme is forced.
   689  func repoRootFromVCSPaths(importPath, scheme string, security web.SecurityMode, vcsPaths []*vcsPath) (*RepoRoot, error) {
   690  	// A common error is to use https://packagepath because that's what
   691  	// hg and git require. Diagnose this helpfully.
   692  	if prefix := httpPrefix(importPath); prefix != "" {
   693  		// The importPath has been cleaned, so has only one slash. The pattern
   694  		// ignores the slashes; the error message puts them back on the RHS at least.
   695  		return nil, fmt.Errorf("%q not allowed in import path", prefix+"//")
   696  	}
   697  	for _, srv := range vcsPaths {
   698  		if !strings.HasPrefix(importPath, srv.prefix) {
   699  			continue
   700  		}
   701  		m := srv.regexp.FindStringSubmatch(importPath)
   702  		if m == nil {
   703  			if srv.prefix != "" {
   704  				return nil, fmt.Errorf("invalid %s import path %q", srv.prefix, importPath)
   705  			}
   706  			continue
   707  		}
   708  
   709  		// Build map of named subexpression matches for expand.
   710  		match := map[string]string{
   711  			"prefix": srv.prefix,
   712  			"import": importPath,
   713  		}
   714  		for i, name := range srv.regexp.SubexpNames() {
   715  			if name != "" && match[name] == "" {
   716  				match[name] = m[i]
   717  			}
   718  		}
   719  		if srv.vcs != "" {
   720  			match["vcs"] = expand(match, srv.vcs)
   721  		}
   722  		if srv.repo != "" {
   723  			match["repo"] = expand(match, srv.repo)
   724  		}
   725  		if srv.check != nil {
   726  			if err := srv.check(match); err != nil {
   727  				return nil, err
   728  			}
   729  		}
   730  		vcs := vcsByCmd(match["vcs"])
   731  		if vcs == nil {
   732  			return nil, fmt.Errorf("unknown version control system %q", match["vcs"])
   733  		}
   734  		if srv.ping {
   735  			if scheme != "" {
   736  				match["repo"] = scheme + "://" + match["repo"]
   737  			} else {
   738  				for _, scheme := range vcs.scheme {
   739  					if security == web.SecureOnly && !vcs.isSecureScheme(scheme) {
   740  						continue
   741  					}
   742  					if vcs.pingCmd != "" && vcs.ping(scheme, match["repo"]) == nil {
   743  						match["repo"] = scheme + "://" + match["repo"]
   744  						goto Found
   745  					}
   746  				}
   747  				// No scheme found. Fall back to the first one.
   748  				match["repo"] = vcs.scheme[0] + "://" + match["repo"]
   749  			Found:
   750  			}
   751  		}
   752  		rr := &RepoRoot{
   753  			Repo: match["repo"],
   754  			Root: match["root"],
   755  			VCS:  vcs.cmd,
   756  			vcs:  vcs,
   757  		}
   758  		return rr, nil
   759  	}
   760  	return nil, errUnknownSite
   761  }
   762  
   763  // urlForImportPath returns a partially-populated URL for the given Go import path.
   764  //
   765  // The URL leaves the Scheme field blank so that web.Get will try any scheme
   766  // allowed by the selected security mode.
   767  func urlForImportPath(importPath string) (*urlpkg.URL, error) {
   768  	slash := strings.Index(importPath, "/")
   769  	if slash < 0 {
   770  		slash = len(importPath)
   771  	}
   772  	host, path := importPath[:slash], importPath[slash:]
   773  	if !strings.Contains(host, ".") {
   774  		return nil, errors.New("import path does not begin with hostname")
   775  	}
   776  	if len(path) == 0 {
   777  		path = "/"
   778  	}
   779  	return &urlpkg.URL{Host: host, Path: path, RawQuery: "go-get=1"}, nil
   780  }
   781  
   782  // repoRootForImportDynamic finds a *RepoRoot for a custom domain that's not
   783  // statically known by repoRootForImportPathStatic.
   784  //
   785  // This handles custom import paths like "name.tld/pkg/foo" or just "name.tld".
   786  func repoRootForImportDynamic(importPath string, mod ModuleMode, security web.SecurityMode) (*RepoRoot, error) {
   787  	url, err := urlForImportPath(importPath)
   788  	if err != nil {
   789  		return nil, err
   790  	}
   791  	resp, err := web.Get(security, url)
   792  	if err != nil {
   793  		msg := "https fetch: %v"
   794  		if security == web.Insecure {
   795  			msg = "http/" + msg
   796  		}
   797  		return nil, fmt.Errorf(msg, err)
   798  	}
   799  	body := resp.Body
   800  	defer body.Close()
   801  	imports, err := parseMetaGoImports(body, mod)
   802  	if err != nil {
   803  		return nil, fmt.Errorf("parsing %s: %v", importPath, err)
   804  	}
   805  	// Find the matched meta import.
   806  	mmi, err := matchGoImport(imports, importPath)
   807  	if err != nil {
   808  		if _, ok := err.(ImportMismatchError); !ok {
   809  			return nil, fmt.Errorf("parse %s: %v", url, err)
   810  		}
   811  		return nil, fmt.Errorf("parse %s: no go-import meta tags (%s)", resp.URL, err)
   812  	}
   813  	if cfg.BuildV {
   814  		log.Printf("get %q: found meta tag %#v at %s", importPath, mmi, url)
   815  	}
   816  	// If the import was "uni.edu/bob/project", which said the
   817  	// prefix was "uni.edu" and the RepoRoot was "evilroot.com",
   818  	// make sure we don't trust Bob and check out evilroot.com to
   819  	// "uni.edu" yet (possibly overwriting/preempting another
   820  	// non-evil student). Instead, first verify the root and see
   821  	// if it matches Bob's claim.
   822  	if mmi.Prefix != importPath {
   823  		if cfg.BuildV {
   824  			log.Printf("get %q: verifying non-authoritative meta tag", importPath)
   825  		}
   826  		var imports []metaImport
   827  		url, imports, err = metaImportsForPrefix(mmi.Prefix, mod, security)
   828  		if err != nil {
   829  			return nil, err
   830  		}
   831  		metaImport2, err := matchGoImport(imports, importPath)
   832  		if err != nil || mmi != metaImport2 {
   833  			return nil, fmt.Errorf("%s and %s disagree about go-import for %s", resp.URL, url, mmi.Prefix)
   834  		}
   835  	}
   836  
   837  	if err := validateRepoRoot(mmi.RepoRoot); err != nil {
   838  		return nil, fmt.Errorf("%s: invalid repo root %q: %v", resp.URL, mmi.RepoRoot, err)
   839  	}
   840  	vcs := vcsByCmd(mmi.VCS)
   841  	if vcs == nil && mmi.VCS != "mod" {
   842  		return nil, fmt.Errorf("%s: unknown vcs %q", resp.URL, mmi.VCS)
   843  	}
   844  
   845  	rr := &RepoRoot{
   846  		Repo:     mmi.RepoRoot,
   847  		Root:     mmi.Prefix,
   848  		IsCustom: true,
   849  		VCS:      mmi.VCS,
   850  		vcs:      vcs,
   851  	}
   852  	return rr, nil
   853  }
   854  
   855  // validateRepoRoot returns an error if repoRoot does not seem to be
   856  // a valid URL with scheme.
   857  func validateRepoRoot(repoRoot string) error {
   858  	url, err := urlpkg.Parse(repoRoot)
   859  	if err != nil {
   860  		return err
   861  	}
   862  	if url.Scheme == "" {
   863  		return errors.New("no scheme")
   864  	}
   865  	if url.Scheme == "file" {
   866  		return errors.New("file scheme disallowed")
   867  	}
   868  	return nil
   869  }
   870  
   871  var fetchGroup singleflight.Group
   872  var (
   873  	fetchCacheMu sync.Mutex
   874  	fetchCache   = map[string]fetchResult{} // key is metaImportsForPrefix's importPrefix
   875  )
   876  
   877  // metaImportsForPrefix takes a package's root import path as declared in a <meta> tag
   878  // and returns its HTML discovery URL and the parsed metaImport lines
   879  // found on the page.
   880  //
   881  // The importPath is of the form "golang.org/x/tools".
   882  // It is an error if no imports are found.
   883  // url will still be valid if err != nil.
   884  // The returned url will be of the form "https://golang.org/x/tools?go-get=1"
   885  func metaImportsForPrefix(importPrefix string, mod ModuleMode, security web.SecurityMode) (*urlpkg.URL, []metaImport, error) {
   886  	setCache := func(res fetchResult) (fetchResult, error) {
   887  		fetchCacheMu.Lock()
   888  		defer fetchCacheMu.Unlock()
   889  		fetchCache[importPrefix] = res
   890  		return res, nil
   891  	}
   892  
   893  	resi, _, _ := fetchGroup.Do(importPrefix, func() (resi interface{}, err error) {
   894  		fetchCacheMu.Lock()
   895  		if res, ok := fetchCache[importPrefix]; ok {
   896  			fetchCacheMu.Unlock()
   897  			return res, nil
   898  		}
   899  		fetchCacheMu.Unlock()
   900  
   901  		url, err := urlForImportPath(importPrefix)
   902  		if err != nil {
   903  			return setCache(fetchResult{err: err})
   904  		}
   905  		resp, err := web.Get(security, url)
   906  		if err != nil {
   907  			return setCache(fetchResult{url: url, err: fmt.Errorf("fetching %s: %v", importPrefix, err)})
   908  		}
   909  		body := resp.Body
   910  		defer body.Close()
   911  		imports, err := parseMetaGoImports(body, mod)
   912  		if err != nil {
   913  			return setCache(fetchResult{url: url, err: fmt.Errorf("parsing %s: %v", resp.URL, err)})
   914  		}
   915  		if len(imports) == 0 {
   916  			err = fmt.Errorf("fetching %s: no go-import meta tag found in %s", importPrefix, resp.URL)
   917  		}
   918  		return setCache(fetchResult{url: url, imports: imports, err: err})
   919  	})
   920  	res := resi.(fetchResult)
   921  	return res.url, res.imports, res.err
   922  }
   923  
   924  type fetchResult struct {
   925  	url     *urlpkg.URL
   926  	imports []metaImport
   927  	err     error
   928  }
   929  
   930  // metaImport represents the parsed <meta name="go-import"
   931  // content="prefix vcs reporoot" /> tags from HTML files.
   932  type metaImport struct {
   933  	Prefix, VCS, RepoRoot string
   934  }
   935  
   936  // pathPrefix reports whether sub is a prefix of s,
   937  // only considering entire path components.
   938  func pathPrefix(s, sub string) bool {
   939  	// strings.HasPrefix is necessary but not sufficient.
   940  	if !strings.HasPrefix(s, sub) {
   941  		return false
   942  	}
   943  	// The remainder after the prefix must either be empty or start with a slash.
   944  	rem := s[len(sub):]
   945  	return rem == "" || rem[0] == '/'
   946  }
   947  
   948  // A ImportMismatchError is returned where metaImport/s are present
   949  // but none match our import path.
   950  type ImportMismatchError struct {
   951  	importPath string
   952  	mismatches []string // the meta imports that were discarded for not matching our importPath
   953  }
   954  
   955  func (m ImportMismatchError) Error() string {
   956  	formattedStrings := make([]string, len(m.mismatches))
   957  	for i, pre := range m.mismatches {
   958  		formattedStrings[i] = fmt.Sprintf("meta tag %s did not match import path %s", pre, m.importPath)
   959  	}
   960  	return strings.Join(formattedStrings, ", ")
   961  }
   962  
   963  // matchGoImport returns the metaImport from imports matching importPath.
   964  // An error is returned if there are multiple matches.
   965  // errNoMatch is returned if none match.
   966  func matchGoImport(imports []metaImport, importPath string) (metaImport, error) {
   967  	match := -1
   968  
   969  	errImportMismatch := ImportMismatchError{importPath: importPath}
   970  	for i, im := range imports {
   971  		if !pathPrefix(importPath, im.Prefix) {
   972  			errImportMismatch.mismatches = append(errImportMismatch.mismatches, im.Prefix)
   973  			continue
   974  		}
   975  
   976  		if match >= 0 {
   977  			if imports[match].VCS == "mod" && im.VCS != "mod" {
   978  				// All the mod entries precede all the non-mod entries.
   979  				// We have a mod entry and don't care about the rest,
   980  				// matching or not.
   981  				break
   982  			}
   983  			return metaImport{}, fmt.Errorf("multiple meta tags match import path %q", importPath)
   984  		}
   985  		match = i
   986  	}
   987  
   988  	if match == -1 {
   989  		return metaImport{}, errImportMismatch
   990  	}
   991  	return imports[match], nil
   992  }
   993  
   994  // expand rewrites s to replace {k} with match[k] for each key k in match.
   995  func expand(match map[string]string, s string) string {
   996  	// We want to replace each match exactly once, and the result of expansion
   997  	// must not depend on the iteration order through the map.
   998  	// A strings.Replacer has exactly the properties we're looking for.
   999  	oldNew := make([]string, 0, 2*len(match))
  1000  	for k, v := range match {
  1001  		oldNew = append(oldNew, "{"+k+"}", v)
  1002  	}
  1003  	return strings.NewReplacer(oldNew...).Replace(s)
  1004  }
  1005  
  1006  // vcsPaths defines the meaning of import paths referring to
  1007  // commonly-used VCS hosting sites (github.com/user/dir)
  1008  // and import paths referring to a fully-qualified importPath
  1009  // containing a VCS type (foo.com/repo.git/dir)
  1010  var vcsPaths = []*vcsPath{
  1011  	// Github
  1012  	{
  1013  		prefix: "github.com/",
  1014  		regexp: lazyregexp.New(`^(?P<root>github\.com/[A-Za-z0-9_.\-]+/[A-Za-z0-9_.\-]+)(/[\p{L}0-9_.\-]+)*$`),
  1015  		vcs:    "git",
  1016  		repo:   "https://{root}",
  1017  		check:  noVCSSuffix,
  1018  	},
  1019  
  1020  	// Bitbucket
  1021  	{
  1022  		prefix: "bitbucket.org/",
  1023  		regexp: lazyregexp.New(`^(?P<root>bitbucket\.org/(?P<bitname>[A-Za-z0-9_.\-]+/[A-Za-z0-9_.\-]+))(/[A-Za-z0-9_.\-]+)*$`),
  1024  		repo:   "https://{root}",
  1025  		check:  bitbucketVCS,
  1026  	},
  1027  
  1028  	// IBM DevOps Services (JazzHub)
  1029  	{
  1030  		prefix: "hub.jazz.net/git/",
  1031  		regexp: lazyregexp.New(`^(?P<root>hub\.jazz\.net/git/[a-z0-9]+/[A-Za-z0-9_.\-]+)(/[A-Za-z0-9_.\-]+)*$`),
  1032  		vcs:    "git",
  1033  		repo:   "https://{root}",
  1034  		check:  noVCSSuffix,
  1035  	},
  1036  
  1037  	// Git at Apache
  1038  	{
  1039  		prefix: "git.apache.org/",
  1040  		regexp: lazyregexp.New(`^(?P<root>git\.apache\.org/[a-z0-9_.\-]+\.git)(/[A-Za-z0-9_.\-]+)*$`),
  1041  		vcs:    "git",
  1042  		repo:   "https://{root}",
  1043  	},
  1044  
  1045  	// Git at OpenStack
  1046  	{
  1047  		prefix: "git.openstack.org/",
  1048  		regexp: lazyregexp.New(`^(?P<root>git\.openstack\.org/[A-Za-z0-9_.\-]+/[A-Za-z0-9_.\-]+)(\.git)?(/[A-Za-z0-9_.\-]+)*$`),
  1049  		vcs:    "git",
  1050  		repo:   "https://{root}",
  1051  	},
  1052  
  1053  	// chiselapp.com for fossil
  1054  	{
  1055  		prefix: "chiselapp.com/",
  1056  		regexp: lazyregexp.New(`^(?P<root>chiselapp\.com/user/[A-Za-z0-9]+/repository/[A-Za-z0-9_.\-]+)$`),
  1057  		vcs:    "fossil",
  1058  		repo:   "https://{root}",
  1059  	},
  1060  
  1061  	// General syntax for any server.
  1062  	// Must be last.
  1063  	{
  1064  		regexp: lazyregexp.New(`(?P<root>(?P<repo>([a-z0-9.\-]+\.)+[a-z0-9.\-]+(:[0-9]+)?(/~?[A-Za-z0-9_.\-]+)+?)\.(?P<vcs>bzr|fossil|git|hg|svn))(/~?[A-Za-z0-9_.\-]+)*$`),
  1065  		ping:   true,
  1066  	},
  1067  }
  1068  
  1069  // vcsPathsAfterDynamic gives additional vcsPaths entries
  1070  // to try after the dynamic HTML check.
  1071  // This gives those sites a chance to introduce <meta> tags
  1072  // as part of a graceful transition away from the hard-coded logic.
  1073  var vcsPathsAfterDynamic = []*vcsPath{
  1074  	// Launchpad. See golang.org/issue/11436.
  1075  	{
  1076  		prefix: "launchpad.net/",
  1077  		regexp: lazyregexp.New(`^(?P<root>launchpad\.net/((?P<project>[A-Za-z0-9_.\-]+)(?P<series>/[A-Za-z0-9_.\-]+)?|~[A-Za-z0-9_.\-]+/(\+junk|[A-Za-z0-9_.\-]+)/[A-Za-z0-9_.\-]+))(/[A-Za-z0-9_.\-]+)*$`),
  1078  		vcs:    "bzr",
  1079  		repo:   "https://{root}",
  1080  		check:  launchpadVCS,
  1081  	},
  1082  }
  1083  
  1084  // noVCSSuffix checks that the repository name does not
  1085  // end in .foo for any version control system foo.
  1086  // The usual culprit is ".git".
  1087  func noVCSSuffix(match map[string]string) error {
  1088  	repo := match["repo"]
  1089  	for _, vcs := range vcsList {
  1090  		if strings.HasSuffix(repo, "."+vcs.cmd) {
  1091  			return fmt.Errorf("invalid version control suffix in %s path", match["prefix"])
  1092  		}
  1093  	}
  1094  	return nil
  1095  }
  1096  
  1097  // bitbucketVCS determines the version control system for a
  1098  // Bitbucket repository, by using the Bitbucket API.
  1099  func bitbucketVCS(match map[string]string) error {
  1100  	if err := noVCSSuffix(match); err != nil {
  1101  		return err
  1102  	}
  1103  
  1104  	var resp struct {
  1105  		SCM string `json:"scm"`
  1106  	}
  1107  	url := &urlpkg.URL{
  1108  		Scheme:   "https",
  1109  		Host:     "api.bitbucket.org",
  1110  		Path:     expand(match, "/2.0/repositories/{bitname}"),
  1111  		RawQuery: "fields=scm",
  1112  	}
  1113  	data, err := web.GetBytes(url)
  1114  	if err != nil {
  1115  		if httpErr, ok := err.(*web.HTTPError); ok && httpErr.StatusCode == 403 {
  1116  			// this may be a private repository. If so, attempt to determine which
  1117  			// VCS it uses. See issue 5375.
  1118  			root := match["root"]
  1119  			for _, vcs := range []string{"git", "hg"} {
  1120  				if vcsByCmd(vcs).ping("https", root) == nil {
  1121  					resp.SCM = vcs
  1122  					break
  1123  				}
  1124  			}
  1125  		}
  1126  
  1127  		if resp.SCM == "" {
  1128  			return err
  1129  		}
  1130  	} else {
  1131  		if err := json.Unmarshal(data, &resp); err != nil {
  1132  			return fmt.Errorf("decoding %s: %v", url, err)
  1133  		}
  1134  	}
  1135  
  1136  	if vcsByCmd(resp.SCM) != nil {
  1137  		match["vcs"] = resp.SCM
  1138  		if resp.SCM == "git" {
  1139  			match["repo"] += ".git"
  1140  		}
  1141  		return nil
  1142  	}
  1143  
  1144  	return fmt.Errorf("unable to detect version control system for bitbucket.org/ path")
  1145  }
  1146  
  1147  // launchpadVCS solves the ambiguity for "lp.net/project/foo". In this case,
  1148  // "foo" could be a series name registered in Launchpad with its own branch,
  1149  // and it could also be the name of a directory within the main project
  1150  // branch one level up.
  1151  func launchpadVCS(match map[string]string) error {
  1152  	if match["project"] == "" || match["series"] == "" {
  1153  		return nil
  1154  	}
  1155  	url := &urlpkg.URL{
  1156  		Scheme: "https",
  1157  		Host:   "code.launchpad.net",
  1158  		Path:   expand(match, "/{project}{series}/.bzr/branch-format"),
  1159  	}
  1160  	_, err := web.GetBytes(url)
  1161  	if err != nil {
  1162  		match["root"] = expand(match, "launchpad.net/{project}")
  1163  		match["repo"] = expand(match, "https://{root}")
  1164  	}
  1165  	return nil
  1166  }
  1167  

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