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

Documentation: cmd/go/internal/vcs

     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 vcs
     6  
     7  import (
     8  	"bytes"
     9  	"errors"
    10  	"fmt"
    11  	"internal/lazyregexp"
    12  	"internal/singleflight"
    13  	"io/fs"
    14  	"log"
    15  	urlpkg "net/url"
    16  	"os"
    17  	"os/exec"
    18  	"path/filepath"
    19  	"regexp"
    20  	"strconv"
    21  	"strings"
    22  	"sync"
    23  	"time"
    24  
    25  	"cmd/go/internal/base"
    26  	"cmd/go/internal/cfg"
    27  	"cmd/go/internal/search"
    28  	"cmd/go/internal/str"
    29  	"cmd/go/internal/web"
    30  
    31  	"golang.org/x/mod/module"
    32  )
    33  
    34  // A Cmd describes how to use a version control system
    35  // like Mercurial, Git, or Subversion.
    36  type Cmd struct {
    37  	Name      string
    38  	Cmd       string     // name of binary to invoke command
    39  	RootNames []rootName // filename and mode indicating the root of a checkout directory
    40  
    41  	CreateCmd   []string // commands to download a fresh copy of a repository
    42  	DownloadCmd []string // commands to download updates into an existing repository
    43  
    44  	TagCmd         []tagCmd // commands to list tags
    45  	TagLookupCmd   []tagCmd // commands to lookup tags before running tagSyncCmd
    46  	TagSyncCmd     []string // commands to sync to specific tag
    47  	TagSyncDefault []string // commands to sync to default tag
    48  
    49  	Scheme  []string
    50  	PingCmd string
    51  
    52  	RemoteRepo  func(v *Cmd, rootDir string) (remoteRepo string, err error)
    53  	ResolveRepo func(v *Cmd, rootDir, remoteRepo string) (realRepo string, err error)
    54  	Status      func(v *Cmd, rootDir string) (Status, error)
    55  }
    56  
    57  // Status is the current state of a local repository.
    58  type Status struct {
    59  	Revision    string    // Optional.
    60  	CommitTime  time.Time // Optional.
    61  	Uncommitted bool      // Required.
    62  }
    63  
    64  var (
    65  	// VCSTestRepoURL is the URL of the HTTP server that serves the repos for
    66  	// vcs-test.golang.org.
    67  	//
    68  	// In tests, this is set to the URL of an httptest.Server hosting a
    69  	// cmd/go/internal/vcweb.Server.
    70  	VCSTestRepoURL string
    71  
    72  	// VCSTestHosts is the set of hosts supported by the vcs-test server.
    73  	VCSTestHosts []string
    74  
    75  	// VCSTestIsLocalHost reports whether the given URL refers to a local
    76  	// (loopback) host, such as "localhost" or "127.0.0.1:8080".
    77  	VCSTestIsLocalHost func(*urlpkg.URL) bool
    78  )
    79  
    80  var defaultSecureScheme = map[string]bool{
    81  	"https":   true,
    82  	"git+ssh": true,
    83  	"bzr+ssh": true,
    84  	"svn+ssh": true,
    85  	"ssh":     true,
    86  }
    87  
    88  func (v *Cmd) IsSecure(repo string) bool {
    89  	u, err := urlpkg.Parse(repo)
    90  	if err != nil {
    91  		// If repo is not a URL, it's not secure.
    92  		return false
    93  	}
    94  	if VCSTestRepoURL != "" && web.IsLocalHost(u) {
    95  		// If the vcstest server is in use, it may redirect to other local ports for
    96  		// other protocols (such as svn). Assume that all loopback addresses are
    97  		// secure during testing.
    98  		return true
    99  	}
   100  	return v.isSecureScheme(u.Scheme)
   101  }
   102  
   103  func (v *Cmd) isSecureScheme(scheme string) bool {
   104  	switch v.Cmd {
   105  	case "git":
   106  		// GIT_ALLOW_PROTOCOL is an environment variable defined by Git. It is a
   107  		// colon-separated list of schemes that are allowed to be used with git
   108  		// fetch/clone. Any scheme not mentioned will be considered insecure.
   109  		if allow := os.Getenv("GIT_ALLOW_PROTOCOL"); allow != "" {
   110  			for _, s := range strings.Split(allow, ":") {
   111  				if s == scheme {
   112  					return true
   113  				}
   114  			}
   115  			return false
   116  		}
   117  	}
   118  	return defaultSecureScheme[scheme]
   119  }
   120  
   121  // A tagCmd describes a command to list available tags
   122  // that can be passed to tagSyncCmd.
   123  type tagCmd struct {
   124  	cmd     string // command to list tags
   125  	pattern string // regexp to extract tags from list
   126  }
   127  
   128  // vcsList lists the known version control systems
   129  var vcsList = []*Cmd{
   130  	vcsHg,
   131  	vcsGit,
   132  	vcsSvn,
   133  	vcsBzr,
   134  	vcsFossil,
   135  }
   136  
   137  // vcsMod is a stub for the "mod" scheme. It's returned by
   138  // repoRootForImportPathDynamic, but is otherwise not treated as a VCS command.
   139  var vcsMod = &Cmd{Name: "mod"}
   140  
   141  // vcsByCmd returns the version control system for the given
   142  // command name (hg, git, svn, bzr).
   143  func vcsByCmd(cmd string) *Cmd {
   144  	for _, vcs := range vcsList {
   145  		if vcs.Cmd == cmd {
   146  			return vcs
   147  		}
   148  	}
   149  	return nil
   150  }
   151  
   152  // vcsHg describes how to use Mercurial.
   153  var vcsHg = &Cmd{
   154  	Name: "Mercurial",
   155  	Cmd:  "hg",
   156  	RootNames: []rootName{
   157  		{filename: ".hg", isDir: true},
   158  	},
   159  
   160  	CreateCmd:   []string{"clone -U -- {repo} {dir}"},
   161  	DownloadCmd: []string{"pull"},
   162  
   163  	// We allow both tag and branch names as 'tags'
   164  	// for selecting a version. This lets people have
   165  	// a go.release.r60 branch and a go1 branch
   166  	// and make changes in both, without constantly
   167  	// editing .hgtags.
   168  	TagCmd: []tagCmd{
   169  		{"tags", `^(\S+)`},
   170  		{"branches", `^(\S+)`},
   171  	},
   172  	TagSyncCmd:     []string{"update -r {tag}"},
   173  	TagSyncDefault: []string{"update default"},
   174  
   175  	Scheme:     []string{"https", "http", "ssh"},
   176  	PingCmd:    "identify -- {scheme}://{repo}",
   177  	RemoteRepo: hgRemoteRepo,
   178  	Status:     hgStatus,
   179  }
   180  
   181  func hgRemoteRepo(vcsHg *Cmd, rootDir string) (remoteRepo string, err error) {
   182  	out, err := vcsHg.runOutput(rootDir, "paths default")
   183  	if err != nil {
   184  		return "", err
   185  	}
   186  	return strings.TrimSpace(string(out)), nil
   187  }
   188  
   189  func hgStatus(vcsHg *Cmd, rootDir string) (Status, error) {
   190  	// Output changeset ID and seconds since epoch.
   191  	out, err := vcsHg.runOutputVerboseOnly(rootDir, `log -l1 -T {node}:{date|hgdate}`)
   192  	if err != nil {
   193  		return Status{}, err
   194  	}
   195  
   196  	// Successful execution without output indicates an empty repo (no commits).
   197  	var rev string
   198  	var commitTime time.Time
   199  	if len(out) > 0 {
   200  		// Strip trailing timezone offset.
   201  		if i := bytes.IndexByte(out, ' '); i > 0 {
   202  			out = out[:i]
   203  		}
   204  		rev, commitTime, err = parseRevTime(out)
   205  		if err != nil {
   206  			return Status{}, err
   207  		}
   208  	}
   209  
   210  	// Also look for untracked files.
   211  	out, err = vcsHg.runOutputVerboseOnly(rootDir, "status")
   212  	if err != nil {
   213  		return Status{}, err
   214  	}
   215  	uncommitted := len(out) > 0
   216  
   217  	return Status{
   218  		Revision:    rev,
   219  		CommitTime:  commitTime,
   220  		Uncommitted: uncommitted,
   221  	}, nil
   222  }
   223  
   224  // parseRevTime parses commit details in "revision:seconds" format.
   225  func parseRevTime(out []byte) (string, time.Time, error) {
   226  	buf := string(bytes.TrimSpace(out))
   227  
   228  	i := strings.IndexByte(buf, ':')
   229  	if i < 1 {
   230  		return "", time.Time{}, errors.New("unrecognized VCS tool output")
   231  	}
   232  	rev := buf[:i]
   233  
   234  	secs, err := strconv.ParseInt(string(buf[i+1:]), 10, 64)
   235  	if err != nil {
   236  		return "", time.Time{}, fmt.Errorf("unrecognized VCS tool output: %v", err)
   237  	}
   238  
   239  	return rev, time.Unix(secs, 0), nil
   240  }
   241  
   242  // vcsGit describes how to use Git.
   243  var vcsGit = &Cmd{
   244  	Name: "Git",
   245  	Cmd:  "git",
   246  	RootNames: []rootName{
   247  		{filename: ".git", isDir: true},
   248  	},
   249  
   250  	CreateCmd:   []string{"clone -- {repo} {dir}", "-go-internal-cd {dir} submodule update --init --recursive"},
   251  	DownloadCmd: []string{"pull --ff-only", "submodule update --init --recursive"},
   252  
   253  	TagCmd: []tagCmd{
   254  		// tags/xxx matches a git tag named xxx
   255  		// origin/xxx matches a git branch named xxx on the default remote repository
   256  		{"show-ref", `(?:tags|origin)/(\S+)$`},
   257  	},
   258  	TagLookupCmd: []tagCmd{
   259  		{"show-ref tags/{tag} origin/{tag}", `((?:tags|origin)/\S+)$`},
   260  	},
   261  	TagSyncCmd: []string{"checkout {tag}", "submodule update --init --recursive"},
   262  	// both createCmd and downloadCmd update the working dir.
   263  	// No need to do more here. We used to 'checkout master'
   264  	// but that doesn't work if the default branch is not named master.
   265  	// DO NOT add 'checkout master' here.
   266  	// See golang.org/issue/9032.
   267  	TagSyncDefault: []string{"submodule update --init --recursive"},
   268  
   269  	Scheme: []string{"git", "https", "http", "git+ssh", "ssh"},
   270  
   271  	// Leave out the '--' separator in the ls-remote command: git 2.7.4 does not
   272  	// support such a separator for that command, and this use should be safe
   273  	// without it because the {scheme} value comes from the predefined list above.
   274  	// See golang.org/issue/33836.
   275  	PingCmd: "ls-remote {scheme}://{repo}",
   276  
   277  	RemoteRepo: gitRemoteRepo,
   278  	Status:     gitStatus,
   279  }
   280  
   281  // scpSyntaxRe matches the SCP-like addresses used by Git to access
   282  // repositories by SSH.
   283  var scpSyntaxRe = lazyregexp.New(`^(\w+)@([\w.-]+):(.*)$`)
   284  
   285  func gitRemoteRepo(vcsGit *Cmd, rootDir string) (remoteRepo string, err error) {
   286  	const cmd = "config remote.origin.url"
   287  	outb, err := vcsGit.run1(rootDir, cmd, nil, false)
   288  	if err != nil {
   289  		// if it doesn't output any message, it means the config argument is correct,
   290  		// but the config value itself doesn't exist
   291  		if outb != nil && len(outb) == 0 {
   292  			return "", errors.New("remote origin not found")
   293  		}
   294  		return "", err
   295  	}
   296  	out := strings.TrimSpace(string(outb))
   297  
   298  	var repoURL *urlpkg.URL
   299  	if m := scpSyntaxRe.FindStringSubmatch(out); m != nil {
   300  		// Match SCP-like syntax and convert it to a URL.
   301  		// Eg, "git@github.com:user/repo" becomes
   302  		// "ssh://git@github.com/user/repo".
   303  		repoURL = &urlpkg.URL{
   304  			Scheme: "ssh",
   305  			User:   urlpkg.User(m[1]),
   306  			Host:   m[2],
   307  			Path:   m[3],
   308  		}
   309  	} else {
   310  		repoURL, err = urlpkg.Parse(out)
   311  		if err != nil {
   312  			return "", err
   313  		}
   314  	}
   315  
   316  	// Iterate over insecure schemes too, because this function simply
   317  	// reports the state of the repo. If we can't see insecure schemes then
   318  	// we can't report the actual repo URL.
   319  	for _, s := range vcsGit.Scheme {
   320  		if repoURL.Scheme == s {
   321  			return repoURL.String(), nil
   322  		}
   323  	}
   324  	return "", errors.New("unable to parse output of git " + cmd)
   325  }
   326  
   327  func gitStatus(vcsGit *Cmd, rootDir string) (Status, error) {
   328  	out, err := vcsGit.runOutputVerboseOnly(rootDir, "status --porcelain")
   329  	if err != nil {
   330  		return Status{}, err
   331  	}
   332  	uncommitted := len(out) > 0
   333  
   334  	// "git status" works for empty repositories, but "git log" does not.
   335  	// Assume there are no commits in the repo when "git log" fails with
   336  	// uncommitted files and skip tagging revision / committime.
   337  	var rev string
   338  	var commitTime time.Time
   339  	out, err = vcsGit.runOutputVerboseOnly(rootDir, "-c log.showsignature=false log -1 --format=%H:%ct")
   340  	if err != nil && !uncommitted {
   341  		return Status{}, err
   342  	} else if err == nil {
   343  		rev, commitTime, err = parseRevTime(out)
   344  		if err != nil {
   345  			return Status{}, err
   346  		}
   347  	}
   348  
   349  	return Status{
   350  		Revision:    rev,
   351  		CommitTime:  commitTime,
   352  		Uncommitted: uncommitted,
   353  	}, nil
   354  }
   355  
   356  // vcsBzr describes how to use Bazaar.
   357  var vcsBzr = &Cmd{
   358  	Name: "Bazaar",
   359  	Cmd:  "bzr",
   360  	RootNames: []rootName{
   361  		{filename: ".bzr", isDir: true},
   362  	},
   363  
   364  	CreateCmd: []string{"branch -- {repo} {dir}"},
   365  
   366  	// Without --overwrite bzr will not pull tags that changed.
   367  	// Replace by --overwrite-tags after http://pad.lv/681792 goes in.
   368  	DownloadCmd: []string{"pull --overwrite"},
   369  
   370  	TagCmd:         []tagCmd{{"tags", `^(\S+)`}},
   371  	TagSyncCmd:     []string{"update -r {tag}"},
   372  	TagSyncDefault: []string{"update -r revno:-1"},
   373  
   374  	Scheme:      []string{"https", "http", "bzr", "bzr+ssh"},
   375  	PingCmd:     "info -- {scheme}://{repo}",
   376  	RemoteRepo:  bzrRemoteRepo,
   377  	ResolveRepo: bzrResolveRepo,
   378  	Status:      bzrStatus,
   379  }
   380  
   381  func bzrRemoteRepo(vcsBzr *Cmd, rootDir string) (remoteRepo string, err error) {
   382  	outb, err := vcsBzr.runOutput(rootDir, "config parent_location")
   383  	if err != nil {
   384  		return "", err
   385  	}
   386  	return strings.TrimSpace(string(outb)), nil
   387  }
   388  
   389  func bzrResolveRepo(vcsBzr *Cmd, rootDir, remoteRepo string) (realRepo string, err error) {
   390  	outb, err := vcsBzr.runOutput(rootDir, "info "+remoteRepo)
   391  	if err != nil {
   392  		return "", err
   393  	}
   394  	out := string(outb)
   395  
   396  	// Expect:
   397  	// ...
   398  	//   (branch root|repository branch): <URL>
   399  	// ...
   400  
   401  	found := false
   402  	for _, prefix := range []string{"\n  branch root: ", "\n  repository branch: "} {
   403  		i := strings.Index(out, prefix)
   404  		if i >= 0 {
   405  			out = out[i+len(prefix):]
   406  			found = true
   407  			break
   408  		}
   409  	}
   410  	if !found {
   411  		return "", fmt.Errorf("unable to parse output of bzr info")
   412  	}
   413  
   414  	i := strings.Index(out, "\n")
   415  	if i < 0 {
   416  		return "", fmt.Errorf("unable to parse output of bzr info")
   417  	}
   418  	out = out[:i]
   419  	return strings.TrimSpace(out), nil
   420  }
   421  
   422  func bzrStatus(vcsBzr *Cmd, rootDir string) (Status, error) {
   423  	outb, err := vcsBzr.runOutputVerboseOnly(rootDir, "version-info")
   424  	if err != nil {
   425  		return Status{}, err
   426  	}
   427  	out := string(outb)
   428  
   429  	// Expect (non-empty repositories only):
   430  	//
   431  	// revision-id: gopher@gopher.net-20211021072330-qshok76wfypw9lpm
   432  	// date: 2021-09-21 12:00:00 +1000
   433  	// ...
   434  	var rev string
   435  	var commitTime time.Time
   436  
   437  	for _, line := range strings.Split(out, "\n") {
   438  		i := strings.IndexByte(line, ':')
   439  		if i < 0 {
   440  			continue
   441  		}
   442  		key := line[:i]
   443  		value := strings.TrimSpace(line[i+1:])
   444  
   445  		switch key {
   446  		case "revision-id":
   447  			rev = value
   448  		case "date":
   449  			var err error
   450  			commitTime, err = time.Parse("2006-01-02 15:04:05 -0700", value)
   451  			if err != nil {
   452  				return Status{}, errors.New("unable to parse output of bzr version-info")
   453  			}
   454  		}
   455  	}
   456  
   457  	outb, err = vcsBzr.runOutputVerboseOnly(rootDir, "status")
   458  	if err != nil {
   459  		return Status{}, err
   460  	}
   461  
   462  	// Skip warning when working directory is set to an older revision.
   463  	if bytes.HasPrefix(outb, []byte("working tree is out of date")) {
   464  		i := bytes.IndexByte(outb, '\n')
   465  		if i < 0 {
   466  			i = len(outb)
   467  		}
   468  		outb = outb[:i]
   469  	}
   470  	uncommitted := len(outb) > 0
   471  
   472  	return Status{
   473  		Revision:    rev,
   474  		CommitTime:  commitTime,
   475  		Uncommitted: uncommitted,
   476  	}, nil
   477  }
   478  
   479  // vcsSvn describes how to use Subversion.
   480  var vcsSvn = &Cmd{
   481  	Name: "Subversion",
   482  	Cmd:  "svn",
   483  	RootNames: []rootName{
   484  		{filename: ".svn", isDir: true},
   485  	},
   486  
   487  	CreateCmd:   []string{"checkout -- {repo} {dir}"},
   488  	DownloadCmd: []string{"update"},
   489  
   490  	// There is no tag command in subversion.
   491  	// The branch information is all in the path names.
   492  
   493  	Scheme:     []string{"https", "http", "svn", "svn+ssh"},
   494  	PingCmd:    "info -- {scheme}://{repo}",
   495  	RemoteRepo: svnRemoteRepo,
   496  }
   497  
   498  func svnRemoteRepo(vcsSvn *Cmd, rootDir string) (remoteRepo string, err error) {
   499  	outb, err := vcsSvn.runOutput(rootDir, "info")
   500  	if err != nil {
   501  		return "", err
   502  	}
   503  	out := string(outb)
   504  
   505  	// Expect:
   506  	//
   507  	//	 ...
   508  	// 	URL: <URL>
   509  	// 	...
   510  	//
   511  	// Note that we're not using the Repository Root line,
   512  	// because svn allows checking out subtrees.
   513  	// The URL will be the URL of the subtree (what we used with 'svn co')
   514  	// while the Repository Root may be a much higher parent.
   515  	i := strings.Index(out, "\nURL: ")
   516  	if i < 0 {
   517  		return "", fmt.Errorf("unable to parse output of svn info")
   518  	}
   519  	out = out[i+len("\nURL: "):]
   520  	i = strings.Index(out, "\n")
   521  	if i < 0 {
   522  		return "", fmt.Errorf("unable to parse output of svn info")
   523  	}
   524  	out = out[:i]
   525  	return strings.TrimSpace(out), nil
   526  }
   527  
   528  // fossilRepoName is the name go get associates with a fossil repository. In the
   529  // real world the file can be named anything.
   530  const fossilRepoName = ".fossil"
   531  
   532  // vcsFossil describes how to use Fossil (fossil-scm.org)
   533  var vcsFossil = &Cmd{
   534  	Name: "Fossil",
   535  	Cmd:  "fossil",
   536  	RootNames: []rootName{
   537  		{filename: ".fslckout", isDir: false},
   538  		{filename: "_FOSSIL_", isDir: false},
   539  	},
   540  
   541  	CreateCmd:   []string{"-go-internal-mkdir {dir} clone -- {repo} " + filepath.Join("{dir}", fossilRepoName), "-go-internal-cd {dir} open .fossil"},
   542  	DownloadCmd: []string{"up"},
   543  
   544  	TagCmd:         []tagCmd{{"tag ls", `(.*)`}},
   545  	TagSyncCmd:     []string{"up tag:{tag}"},
   546  	TagSyncDefault: []string{"up trunk"},
   547  
   548  	Scheme:     []string{"https", "http"},
   549  	RemoteRepo: fossilRemoteRepo,
   550  	Status:     fossilStatus,
   551  }
   552  
   553  func fossilRemoteRepo(vcsFossil *Cmd, rootDir string) (remoteRepo string, err error) {
   554  	out, err := vcsFossil.runOutput(rootDir, "remote-url")
   555  	if err != nil {
   556  		return "", err
   557  	}
   558  	return strings.TrimSpace(string(out)), nil
   559  }
   560  
   561  var errFossilInfo = errors.New("unable to parse output of fossil info")
   562  
   563  func fossilStatus(vcsFossil *Cmd, rootDir string) (Status, error) {
   564  	outb, err := vcsFossil.runOutputVerboseOnly(rootDir, "info")
   565  	if err != nil {
   566  		return Status{}, err
   567  	}
   568  	out := string(outb)
   569  
   570  	// Expect:
   571  	// ...
   572  	// checkout:     91ed71f22c77be0c3e250920f47bfd4e1f9024d2 2021-09-21 12:00:00 UTC
   573  	// ...
   574  
   575  	// Extract revision and commit time.
   576  	// Ensure line ends with UTC (known timezone offset).
   577  	const prefix = "\ncheckout:"
   578  	const suffix = " UTC"
   579  	i := strings.Index(out, prefix)
   580  	if i < 0 {
   581  		return Status{}, errFossilInfo
   582  	}
   583  	checkout := out[i+len(prefix):]
   584  	i = strings.Index(checkout, suffix)
   585  	if i < 0 {
   586  		return Status{}, errFossilInfo
   587  	}
   588  	checkout = strings.TrimSpace(checkout[:i])
   589  
   590  	i = strings.IndexByte(checkout, ' ')
   591  	if i < 0 {
   592  		return Status{}, errFossilInfo
   593  	}
   594  	rev := checkout[:i]
   595  
   596  	commitTime, err := time.ParseInLocation(time.DateTime, checkout[i+1:], time.UTC)
   597  	if err != nil {
   598  		return Status{}, fmt.Errorf("%v: %v", errFossilInfo, err)
   599  	}
   600  
   601  	// Also look for untracked changes.
   602  	outb, err = vcsFossil.runOutputVerboseOnly(rootDir, "changes --differ")
   603  	if err != nil {
   604  		return Status{}, err
   605  	}
   606  	uncommitted := len(outb) > 0
   607  
   608  	return Status{
   609  		Revision:    rev,
   610  		CommitTime:  commitTime,
   611  		Uncommitted: uncommitted,
   612  	}, nil
   613  }
   614  
   615  func (v *Cmd) String() string {
   616  	return v.Name
   617  }
   618  
   619  // run runs the command line cmd in the given directory.
   620  // keyval is a list of key, value pairs. run expands
   621  // instances of {key} in cmd into value, but only after
   622  // splitting cmd into individual arguments.
   623  // If an error occurs, run prints the command line and the
   624  // command's combined stdout+stderr to standard error.
   625  // Otherwise run discards the command's output.
   626  func (v *Cmd) run(dir string, cmd string, keyval ...string) error {
   627  	_, err := v.run1(dir, cmd, keyval, true)
   628  	return err
   629  }
   630  
   631  // runVerboseOnly is like run but only generates error output to standard error in verbose mode.
   632  func (v *Cmd) runVerboseOnly(dir string, cmd string, keyval ...string) error {
   633  	_, err := v.run1(dir, cmd, keyval, false)
   634  	return err
   635  }
   636  
   637  // runOutput is like run but returns the output of the command.
   638  func (v *Cmd) runOutput(dir string, cmd string, keyval ...string) ([]byte, error) {
   639  	return v.run1(dir, cmd, keyval, true)
   640  }
   641  
   642  // runOutputVerboseOnly is like runOutput but only generates error output to
   643  // standard error in verbose mode.
   644  func (v *Cmd) runOutputVerboseOnly(dir string, cmd string, keyval ...string) ([]byte, error) {
   645  	return v.run1(dir, cmd, keyval, false)
   646  }
   647  
   648  // run1 is the generalized implementation of run and runOutput.
   649  func (v *Cmd) run1(dir string, cmdline string, keyval []string, verbose bool) ([]byte, error) {
   650  	m := make(map[string]string)
   651  	for i := 0; i < len(keyval); i += 2 {
   652  		m[keyval[i]] = keyval[i+1]
   653  	}
   654  	args := strings.Fields(cmdline)
   655  	for i, arg := range args {
   656  		args[i] = expand(m, arg)
   657  	}
   658  
   659  	if len(args) >= 2 && args[0] == "-go-internal-mkdir" {
   660  		var err error
   661  		if filepath.IsAbs(args[1]) {
   662  			err = os.Mkdir(args[1], fs.ModePerm)
   663  		} else {
   664  			err = os.Mkdir(filepath.Join(dir, args[1]), fs.ModePerm)
   665  		}
   666  		if err != nil {
   667  			return nil, err
   668  		}
   669  		args = args[2:]
   670  	}
   671  
   672  	if len(args) >= 2 && args[0] == "-go-internal-cd" {
   673  		if filepath.IsAbs(args[1]) {
   674  			dir = args[1]
   675  		} else {
   676  			dir = filepath.Join(dir, args[1])
   677  		}
   678  		args = args[2:]
   679  	}
   680  
   681  	_, err := cfg.LookPath(v.Cmd)
   682  	if err != nil {
   683  		fmt.Fprintf(os.Stderr,
   684  			"go: missing %s command. See https://golang.org/s/gogetcmd\n",
   685  			v.Name)
   686  		return nil, err
   687  	}
   688  
   689  	cmd := exec.Command(v.Cmd, args...)
   690  	cmd.Dir = dir
   691  	if cfg.BuildX {
   692  		fmt.Fprintf(os.Stderr, "cd %s\n", dir)
   693  		fmt.Fprintf(os.Stderr, "%s %s\n", v.Cmd, strings.Join(args, " "))
   694  	}
   695  	out, err := cmd.Output()
   696  	if err != nil {
   697  		if verbose || cfg.BuildV {
   698  			fmt.Fprintf(os.Stderr, "# cd %s; %s %s\n", dir, v.Cmd, strings.Join(args, " "))
   699  			if ee, ok := err.(*exec.ExitError); ok && len(ee.Stderr) > 0 {
   700  				os.Stderr.Write(ee.Stderr)
   701  			} else {
   702  				fmt.Fprintln(os.Stderr, err.Error())
   703  			}
   704  		}
   705  	}
   706  	return out, err
   707  }
   708  
   709  // Ping pings to determine scheme to use.
   710  func (v *Cmd) Ping(scheme, repo string) error {
   711  	// Run the ping command in an arbitrary working directory,
   712  	// but don't let the current working directory pollute the results.
   713  	// In module mode, we expect GOMODCACHE to exist and be a safe place for
   714  	// commands; in GOPATH mode, we expect that to be true of GOPATH/src.
   715  	dir := cfg.GOMODCACHE
   716  	if !cfg.ModulesEnabled {
   717  		dir = filepath.Join(cfg.BuildContext.GOPATH, "src")
   718  	}
   719  	os.MkdirAll(dir, 0777) // Ignore errors — if unsuccessful, the command will likely fail.
   720  
   721  	release, err := base.AcquireNet()
   722  	if err != nil {
   723  		return err
   724  	}
   725  	defer release()
   726  
   727  	return v.runVerboseOnly(dir, v.PingCmd, "scheme", scheme, "repo", repo)
   728  }
   729  
   730  // Create creates a new copy of repo in dir.
   731  // The parent of dir must exist; dir must not.
   732  func (v *Cmd) Create(dir, repo string) error {
   733  	release, err := base.AcquireNet()
   734  	if err != nil {
   735  		return err
   736  	}
   737  	defer release()
   738  
   739  	for _, cmd := range v.CreateCmd {
   740  		if err := v.run(filepath.Dir(dir), cmd, "dir", dir, "repo", repo); err != nil {
   741  			return err
   742  		}
   743  	}
   744  	return nil
   745  }
   746  
   747  // Download downloads any new changes for the repo in dir.
   748  func (v *Cmd) Download(dir string) error {
   749  	release, err := base.AcquireNet()
   750  	if err != nil {
   751  		return err
   752  	}
   753  	defer release()
   754  
   755  	for _, cmd := range v.DownloadCmd {
   756  		if err := v.run(dir, cmd); err != nil {
   757  			return err
   758  		}
   759  	}
   760  	return nil
   761  }
   762  
   763  // Tags returns the list of available tags for the repo in dir.
   764  func (v *Cmd) Tags(dir string) ([]string, error) {
   765  	var tags []string
   766  	for _, tc := range v.TagCmd {
   767  		out, err := v.runOutput(dir, tc.cmd)
   768  		if err != nil {
   769  			return nil, err
   770  		}
   771  		re := regexp.MustCompile(`(?m-s)` + tc.pattern)
   772  		for _, m := range re.FindAllStringSubmatch(string(out), -1) {
   773  			tags = append(tags, m[1])
   774  		}
   775  	}
   776  	return tags, nil
   777  }
   778  
   779  // TagSync syncs the repo in dir to the named tag,
   780  // which either is a tag returned by tags or is v.tagDefault.
   781  func (v *Cmd) TagSync(dir, tag string) error {
   782  	if v.TagSyncCmd == nil {
   783  		return nil
   784  	}
   785  	if tag != "" {
   786  		for _, tc := range v.TagLookupCmd {
   787  			out, err := v.runOutput(dir, tc.cmd, "tag", tag)
   788  			if err != nil {
   789  				return err
   790  			}
   791  			re := regexp.MustCompile(`(?m-s)` + tc.pattern)
   792  			m := re.FindStringSubmatch(string(out))
   793  			if len(m) > 1 {
   794  				tag = m[1]
   795  				break
   796  			}
   797  		}
   798  	}
   799  
   800  	release, err := base.AcquireNet()
   801  	if err != nil {
   802  		return err
   803  	}
   804  	defer release()
   805  
   806  	if tag == "" && v.TagSyncDefault != nil {
   807  		for _, cmd := range v.TagSyncDefault {
   808  			if err := v.run(dir, cmd); err != nil {
   809  				return err
   810  			}
   811  		}
   812  		return nil
   813  	}
   814  
   815  	for _, cmd := range v.TagSyncCmd {
   816  		if err := v.run(dir, cmd, "tag", tag); err != nil {
   817  			return err
   818  		}
   819  	}
   820  	return nil
   821  }
   822  
   823  // A vcsPath describes how to convert an import path into a
   824  // version control system and repository name.
   825  type vcsPath struct {
   826  	pathPrefix     string                              // prefix this description applies to
   827  	regexp         *lazyregexp.Regexp                  // compiled pattern for import path
   828  	repo           string                              // repository to use (expand with match of re)
   829  	vcs            string                              // version control system to use (expand with match of re)
   830  	check          func(match map[string]string) error // additional checks
   831  	schemelessRepo bool                                // if true, the repo pattern lacks a scheme
   832  }
   833  
   834  // FromDir inspects dir and its parents to determine the
   835  // version control system and code repository to use.
   836  // If no repository is found, FromDir returns an error
   837  // equivalent to os.ErrNotExist.
   838  func FromDir(dir, srcRoot string, allowNesting bool) (repoDir string, vcsCmd *Cmd, err error) {
   839  	// Clean and double-check that dir is in (a subdirectory of) srcRoot.
   840  	dir = filepath.Clean(dir)
   841  	if srcRoot != "" {
   842  		srcRoot = filepath.Clean(srcRoot)
   843  		if len(dir) <= len(srcRoot) || dir[len(srcRoot)] != filepath.Separator {
   844  			return "", nil, fmt.Errorf("directory %q is outside source root %q", dir, srcRoot)
   845  		}
   846  	}
   847  
   848  	origDir := dir
   849  	for len(dir) > len(srcRoot) {
   850  		for _, vcs := range vcsList {
   851  			if isVCSRoot(dir, vcs.RootNames) {
   852  				// Record first VCS we find.
   853  				// If allowNesting is false (as it is in GOPATH), keep looking for
   854  				// repositories in parent directories and report an error if one is
   855  				// found to mitigate VCS injection attacks.
   856  				if vcsCmd == nil {
   857  					vcsCmd = vcs
   858  					repoDir = dir
   859  					if allowNesting {
   860  						return repoDir, vcsCmd, nil
   861  					}
   862  					continue
   863  				}
   864  				// Otherwise, we have one VCS inside a different VCS.
   865  				return "", nil, fmt.Errorf("directory %q uses %s, but parent %q uses %s",
   866  					repoDir, vcsCmd.Cmd, dir, vcs.Cmd)
   867  			}
   868  		}
   869  
   870  		// Move to parent.
   871  		ndir := filepath.Dir(dir)
   872  		if len(ndir) >= len(dir) {
   873  			break
   874  		}
   875  		dir = ndir
   876  	}
   877  	if vcsCmd == nil {
   878  		return "", nil, &vcsNotFoundError{dir: origDir}
   879  	}
   880  	return repoDir, vcsCmd, nil
   881  }
   882  
   883  // isVCSRoot identifies a VCS root by checking whether the directory contains
   884  // any of the listed root names.
   885  func isVCSRoot(dir string, rootNames []rootName) bool {
   886  	for _, root := range rootNames {
   887  		fi, err := os.Stat(filepath.Join(dir, root.filename))
   888  		if err == nil && fi.IsDir() == root.isDir {
   889  			return true
   890  		}
   891  	}
   892  
   893  	return false
   894  }
   895  
   896  type rootName struct {
   897  	filename string
   898  	isDir    bool
   899  }
   900  
   901  type vcsNotFoundError struct {
   902  	dir string
   903  }
   904  
   905  func (e *vcsNotFoundError) Error() string {
   906  	return fmt.Sprintf("directory %q is not using a known version control system", e.dir)
   907  }
   908  
   909  func (e *vcsNotFoundError) Is(err error) bool {
   910  	return err == os.ErrNotExist
   911  }
   912  
   913  // A govcsRule is a single GOVCS rule like private:hg|svn.
   914  type govcsRule struct {
   915  	pattern string
   916  	allowed []string
   917  }
   918  
   919  // A govcsConfig is a full GOVCS configuration.
   920  type govcsConfig []govcsRule
   921  
   922  func parseGOVCS(s string) (govcsConfig, error) {
   923  	s = strings.TrimSpace(s)
   924  	if s == "" {
   925  		return nil, nil
   926  	}
   927  	var cfg govcsConfig
   928  	have := make(map[string]string)
   929  	for _, item := range strings.Split(s, ",") {
   930  		item = strings.TrimSpace(item)
   931  		if item == "" {
   932  			return nil, fmt.Errorf("empty entry in GOVCS")
   933  		}
   934  		pattern, list, found := strings.Cut(item, ":")
   935  		if !found {
   936  			return nil, fmt.Errorf("malformed entry in GOVCS (missing colon): %q", item)
   937  		}
   938  		pattern, list = strings.TrimSpace(pattern), strings.TrimSpace(list)
   939  		if pattern == "" {
   940  			return nil, fmt.Errorf("empty pattern in GOVCS: %q", item)
   941  		}
   942  		if list == "" {
   943  			return nil, fmt.Errorf("empty VCS list in GOVCS: %q", item)
   944  		}
   945  		if search.IsRelativePath(pattern) {
   946  			return nil, fmt.Errorf("relative pattern not allowed in GOVCS: %q", pattern)
   947  		}
   948  		if old := have[pattern]; old != "" {
   949  			return nil, fmt.Errorf("unreachable pattern in GOVCS: %q after %q", item, old)
   950  		}
   951  		have[pattern] = item
   952  		allowed := strings.Split(list, "|")
   953  		for i, a := range allowed {
   954  			a = strings.TrimSpace(a)
   955  			if a == "" {
   956  				return nil, fmt.Errorf("empty VCS name in GOVCS: %q", item)
   957  			}
   958  			allowed[i] = a
   959  		}
   960  		cfg = append(cfg, govcsRule{pattern, allowed})
   961  	}
   962  	return cfg, nil
   963  }
   964  
   965  func (c *govcsConfig) allow(path string, private bool, vcs string) bool {
   966  	for _, rule := range *c {
   967  		match := false
   968  		switch rule.pattern {
   969  		case "private":
   970  			match = private
   971  		case "public":
   972  			match = !private
   973  		default:
   974  			// Note: rule.pattern is known to be comma-free,
   975  			// so MatchPrefixPatterns is only matching a single pattern for us.
   976  			match = module.MatchPrefixPatterns(rule.pattern, path)
   977  		}
   978  		if !match {
   979  			continue
   980  		}
   981  		for _, allow := range rule.allowed {
   982  			if allow == vcs || allow == "all" {
   983  				return true
   984  			}
   985  		}
   986  		return false
   987  	}
   988  
   989  	// By default, nothing is allowed.
   990  	return false
   991  }
   992  
   993  var (
   994  	govcs     govcsConfig
   995  	govcsErr  error
   996  	govcsOnce sync.Once
   997  )
   998  
   999  // defaultGOVCS is the default setting for GOVCS.
  1000  // Setting GOVCS adds entries ahead of these but does not remove them.
  1001  // (They are appended to the parsed GOVCS setting.)
  1002  //
  1003  // The rationale behind allowing only Git and Mercurial is that
  1004  // these two systems have had the most attention to issues
  1005  // of being run as clients of untrusted servers. In contrast,
  1006  // Bazaar, Fossil, and Subversion have primarily been used
  1007  // in trusted, authenticated environments and are not as well
  1008  // scrutinized as attack surfaces.
  1009  //
  1010  // See golang.org/issue/41730 for details.
  1011  var defaultGOVCS = govcsConfig{
  1012  	{"private", []string{"all"}},
  1013  	{"public", []string{"git", "hg"}},
  1014  }
  1015  
  1016  // checkGOVCS checks whether the policy defined by the environment variable
  1017  // GOVCS allows the given vcs command to be used with the given repository
  1018  // root path. Note that root may not be a real package or module path; it's
  1019  // the same as the root path in the go-import meta tag.
  1020  func checkGOVCS(vcs *Cmd, root string) error {
  1021  	if vcs == vcsMod {
  1022  		// Direct module (proxy protocol) fetches don't
  1023  		// involve an external version control system
  1024  		// and are always allowed.
  1025  		return nil
  1026  	}
  1027  
  1028  	govcsOnce.Do(func() {
  1029  		govcs, govcsErr = parseGOVCS(os.Getenv("GOVCS"))
  1030  		govcs = append(govcs, defaultGOVCS...)
  1031  	})
  1032  	if govcsErr != nil {
  1033  		return govcsErr
  1034  	}
  1035  
  1036  	private := module.MatchPrefixPatterns(cfg.GOPRIVATE, root)
  1037  	if !govcs.allow(root, private, vcs.Cmd) {
  1038  		what := "public"
  1039  		if private {
  1040  			what = "private"
  1041  		}
  1042  		return fmt.Errorf("GOVCS disallows using %s for %s %s; see 'go help vcs'", vcs.Cmd, what, root)
  1043  	}
  1044  
  1045  	return nil
  1046  }
  1047  
  1048  // RepoRoot describes the repository root for a tree of source code.
  1049  type RepoRoot struct {
  1050  	Repo     string // repository URL, including scheme
  1051  	Root     string // import path corresponding to root of repo
  1052  	IsCustom bool   // defined by served <meta> tags (as opposed to hard-coded pattern)
  1053  	VCS      *Cmd
  1054  }
  1055  
  1056  func httpPrefix(s string) string {
  1057  	for _, prefix := range [...]string{"http:", "https:"} {
  1058  		if strings.HasPrefix(s, prefix) {
  1059  			return prefix
  1060  		}
  1061  	}
  1062  	return ""
  1063  }
  1064  
  1065  // ModuleMode specifies whether to prefer modules when looking up code sources.
  1066  type ModuleMode int
  1067  
  1068  const (
  1069  	IgnoreMod ModuleMode = iota
  1070  	PreferMod
  1071  )
  1072  
  1073  // RepoRootForImportPath analyzes importPath to determine the
  1074  // version control system, and code repository to use.
  1075  func RepoRootForImportPath(importPath string, mod ModuleMode, security web.SecurityMode) (*RepoRoot, error) {
  1076  	rr, err := repoRootFromVCSPaths(importPath, security, vcsPaths)
  1077  	if err == errUnknownSite {
  1078  		rr, err = repoRootForImportDynamic(importPath, mod, security)
  1079  		if err != nil {
  1080  			err = importErrorf(importPath, "unrecognized import path %q: %v", importPath, err)
  1081  		}
  1082  	}
  1083  	if err != nil {
  1084  		rr1, err1 := repoRootFromVCSPaths(importPath, security, vcsPathsAfterDynamic)
  1085  		if err1 == nil {
  1086  			rr = rr1
  1087  			err = nil
  1088  		}
  1089  	}
  1090  
  1091  	// Should have been taken care of above, but make sure.
  1092  	if err == nil && strings.Contains(importPath, "...") && strings.Contains(rr.Root, "...") {
  1093  		// Do not allow wildcards in the repo root.
  1094  		rr = nil
  1095  		err = importErrorf(importPath, "cannot expand ... in %q", importPath)
  1096  	}
  1097  	return rr, err
  1098  }
  1099  
  1100  var errUnknownSite = errors.New("dynamic lookup required to find mapping")
  1101  
  1102  // repoRootFromVCSPaths attempts to map importPath to a repoRoot
  1103  // using the mappings defined in vcsPaths.
  1104  func repoRootFromVCSPaths(importPath string, security web.SecurityMode, vcsPaths []*vcsPath) (*RepoRoot, error) {
  1105  	if str.HasPathPrefix(importPath, "example.net") {
  1106  		// TODO(rsc): This should not be necessary, but it's required to keep
  1107  		// tests like ../../testdata/script/mod_get_extra.txt from using the network.
  1108  		// That script has everything it needs in the replacement set, but it is still
  1109  		// doing network calls.
  1110  		return nil, fmt.Errorf("no modules on example.net")
  1111  	}
  1112  	if importPath == "rsc.io" {
  1113  		// This special case allows tests like ../../testdata/script/govcs.txt
  1114  		// to avoid making any network calls. The module lookup for a path
  1115  		// like rsc.io/nonexist.svn/foo needs to not make a network call for
  1116  		// a lookup on rsc.io.
  1117  		return nil, fmt.Errorf("rsc.io is not a module")
  1118  	}
  1119  	// A common error is to use https://packagepath because that's what
  1120  	// hg and git require. Diagnose this helpfully.
  1121  	if prefix := httpPrefix(importPath); prefix != "" {
  1122  		// The importPath has been cleaned, so has only one slash. The pattern
  1123  		// ignores the slashes; the error message puts them back on the RHS at least.
  1124  		return nil, fmt.Errorf("%q not allowed in import path", prefix+"//")
  1125  	}
  1126  	for _, srv := range vcsPaths {
  1127  		if !str.HasPathPrefix(importPath, srv.pathPrefix) {
  1128  			continue
  1129  		}
  1130  		m := srv.regexp.FindStringSubmatch(importPath)
  1131  		if m == nil {
  1132  			if srv.pathPrefix != "" {
  1133  				return nil, importErrorf(importPath, "invalid %s import path %q", srv.pathPrefix, importPath)
  1134  			}
  1135  			continue
  1136  		}
  1137  
  1138  		// Build map of named subexpression matches for expand.
  1139  		match := map[string]string{
  1140  			"prefix": srv.pathPrefix + "/",
  1141  			"import": importPath,
  1142  		}
  1143  		for i, name := range srv.regexp.SubexpNames() {
  1144  			if name != "" && match[name] == "" {
  1145  				match[name] = m[i]
  1146  			}
  1147  		}
  1148  		if srv.vcs != "" {
  1149  			match["vcs"] = expand(match, srv.vcs)
  1150  		}
  1151  		if srv.repo != "" {
  1152  			match["repo"] = expand(match, srv.repo)
  1153  		}
  1154  		if srv.check != nil {
  1155  			if err := srv.check(match); err != nil {
  1156  				return nil, err
  1157  			}
  1158  		}
  1159  		vcs := vcsByCmd(match["vcs"])
  1160  		if vcs == nil {
  1161  			return nil, fmt.Errorf("unknown version control system %q", match["vcs"])
  1162  		}
  1163  		if err := checkGOVCS(vcs, match["root"]); err != nil {
  1164  			return nil, err
  1165  		}
  1166  		var repoURL string
  1167  		if !srv.schemelessRepo {
  1168  			repoURL = match["repo"]
  1169  		} else {
  1170  			repo := match["repo"]
  1171  			var ok bool
  1172  			repoURL, ok = interceptVCSTest(repo, vcs, security)
  1173  			if !ok {
  1174  				scheme, err := func() (string, error) {
  1175  					for _, s := range vcs.Scheme {
  1176  						if security == web.SecureOnly && !vcs.isSecureScheme(s) {
  1177  							continue
  1178  						}
  1179  
  1180  						// If we know how to ping URL schemes for this VCS,
  1181  						// check that this repo works.
  1182  						// Otherwise, default to the first scheme
  1183  						// that meets the requested security level.
  1184  						if vcs.PingCmd == "" {
  1185  							return s, nil
  1186  						}
  1187  						if err := vcs.Ping(s, repo); err == nil {
  1188  							return s, nil
  1189  						}
  1190  					}
  1191  					securityFrag := ""
  1192  					if security == web.SecureOnly {
  1193  						securityFrag = "secure "
  1194  					}
  1195  					return "", fmt.Errorf("no %sprotocol found for repository", securityFrag)
  1196  				}()
  1197  				if err != nil {
  1198  					return nil, err
  1199  				}
  1200  				repoURL = scheme + "://" + repo
  1201  			}
  1202  		}
  1203  		rr := &RepoRoot{
  1204  			Repo: repoURL,
  1205  			Root: match["root"],
  1206  			VCS:  vcs,
  1207  		}
  1208  		return rr, nil
  1209  	}
  1210  	return nil, errUnknownSite
  1211  }
  1212  
  1213  func interceptVCSTest(repo string, vcs *Cmd, security web.SecurityMode) (repoURL string, ok bool) {
  1214  	if VCSTestRepoURL == "" {
  1215  		return "", false
  1216  	}
  1217  	if vcs == vcsMod {
  1218  		// Since the "mod" protocol is implemented internally,
  1219  		// requests will be intercepted at a lower level (in cmd/go/internal/web).
  1220  		return "", false
  1221  	}
  1222  
  1223  	if scheme, path, ok := strings.Cut(repo, "://"); ok {
  1224  		if security == web.SecureOnly && !vcs.isSecureScheme(scheme) {
  1225  			return "", false // Let the caller reject the original URL.
  1226  		}
  1227  		repo = path // Remove leading URL scheme if present.
  1228  	}
  1229  	for _, host := range VCSTestHosts {
  1230  		if !str.HasPathPrefix(repo, host) {
  1231  			continue
  1232  		}
  1233  
  1234  		httpURL := VCSTestRepoURL + strings.TrimPrefix(repo, host)
  1235  
  1236  		if vcs == vcsSvn {
  1237  			// Ping the vcweb HTTP server to tell it to initialize the SVN repository
  1238  			// and get the SVN server URL.
  1239  			u, err := urlpkg.Parse(httpURL + "?vcwebsvn=1")
  1240  			if err != nil {
  1241  				panic(fmt.Sprintf("invalid vcs-test repo URL: %v", err))
  1242  			}
  1243  			svnURL, err := web.GetBytes(u)
  1244  			svnURL = bytes.TrimSpace(svnURL)
  1245  			if err == nil && len(svnURL) > 0 {
  1246  				return string(svnURL) + strings.TrimPrefix(repo, host), true
  1247  			}
  1248  
  1249  			// vcs-test doesn't have a svn handler for the given path,
  1250  			// so resolve the repo to HTTPS instead.
  1251  		}
  1252  
  1253  		return httpURL, true
  1254  	}
  1255  	return "", false
  1256  }
  1257  
  1258  // urlForImportPath returns a partially-populated URL for the given Go import path.
  1259  //
  1260  // The URL leaves the Scheme field blank so that web.Get will try any scheme
  1261  // allowed by the selected security mode.
  1262  func urlForImportPath(importPath string) (*urlpkg.URL, error) {
  1263  	slash := strings.Index(importPath, "/")
  1264  	if slash < 0 {
  1265  		slash = len(importPath)
  1266  	}
  1267  	host, path := importPath[:slash], importPath[slash:]
  1268  	if !strings.Contains(host, ".") {
  1269  		return nil, errors.New("import path does not begin with hostname")
  1270  	}
  1271  	if len(path) == 0 {
  1272  		path = "/"
  1273  	}
  1274  	return &urlpkg.URL{Host: host, Path: path, RawQuery: "go-get=1"}, nil
  1275  }
  1276  
  1277  // repoRootForImportDynamic finds a *RepoRoot for a custom domain that's not
  1278  // statically known by repoRootFromVCSPaths.
  1279  //
  1280  // This handles custom import paths like "name.tld/pkg/foo" or just "name.tld".
  1281  func repoRootForImportDynamic(importPath string, mod ModuleMode, security web.SecurityMode) (*RepoRoot, error) {
  1282  	url, err := urlForImportPath(importPath)
  1283  	if err != nil {
  1284  		return nil, err
  1285  	}
  1286  	resp, err := web.Get(security, url)
  1287  	if err != nil {
  1288  		msg := "https fetch: %v"
  1289  		if security == web.Insecure {
  1290  			msg = "http/" + msg
  1291  		}
  1292  		return nil, fmt.Errorf(msg, err)
  1293  	}
  1294  	body := resp.Body
  1295  	defer body.Close()
  1296  	imports, err := parseMetaGoImports(body, mod)
  1297  	if len(imports) == 0 {
  1298  		if respErr := resp.Err(); respErr != nil {
  1299  			// If the server's status was not OK, prefer to report that instead of
  1300  			// an XML parse error.
  1301  			return nil, respErr
  1302  		}
  1303  	}
  1304  	if err != nil {
  1305  		return nil, fmt.Errorf("parsing %s: %v", importPath, err)
  1306  	}
  1307  	// Find the matched meta import.
  1308  	mmi, err := matchGoImport(imports, importPath)
  1309  	if err != nil {
  1310  		if _, ok := err.(ImportMismatchError); !ok {
  1311  			return nil, fmt.Errorf("parse %s: %v", url, err)
  1312  		}
  1313  		return nil, fmt.Errorf("parse %s: no go-import meta tags (%s)", resp.URL, err)
  1314  	}
  1315  	if cfg.BuildV {
  1316  		log.Printf("get %q: found meta tag %#v at %s", importPath, mmi, url)
  1317  	}
  1318  	// If the import was "uni.edu/bob/project", which said the
  1319  	// prefix was "uni.edu" and the RepoRoot was "evilroot.com",
  1320  	// make sure we don't trust Bob and check out evilroot.com to
  1321  	// "uni.edu" yet (possibly overwriting/preempting another
  1322  	// non-evil student). Instead, first verify the root and see
  1323  	// if it matches Bob's claim.
  1324  	if mmi.Prefix != importPath {
  1325  		if cfg.BuildV {
  1326  			log.Printf("get %q: verifying non-authoritative meta tag", importPath)
  1327  		}
  1328  		var imports []metaImport
  1329  		url, imports, err = metaImportsForPrefix(mmi.Prefix, mod, security)
  1330  		if err != nil {
  1331  			return nil, err
  1332  		}
  1333  		metaImport2, err := matchGoImport(imports, importPath)
  1334  		if err != nil || mmi != metaImport2 {
  1335  			return nil, fmt.Errorf("%s and %s disagree about go-import for %s", resp.URL, url, mmi.Prefix)
  1336  		}
  1337  	}
  1338  
  1339  	if err := validateRepoRoot(mmi.RepoRoot); err != nil {
  1340  		return nil, fmt.Errorf("%s: invalid repo root %q: %v", resp.URL, mmi.RepoRoot, err)
  1341  	}
  1342  	var vcs *Cmd
  1343  	if mmi.VCS == "mod" {
  1344  		vcs = vcsMod
  1345  	} else {
  1346  		vcs = vcsByCmd(mmi.VCS)
  1347  		if vcs == nil {
  1348  			return nil, fmt.Errorf("%s: unknown vcs %q", resp.URL, mmi.VCS)
  1349  		}
  1350  	}
  1351  
  1352  	if err := checkGOVCS(vcs, mmi.Prefix); err != nil {
  1353  		return nil, err
  1354  	}
  1355  
  1356  	repoURL, ok := interceptVCSTest(mmi.RepoRoot, vcs, security)
  1357  	if !ok {
  1358  		repoURL = mmi.RepoRoot
  1359  	}
  1360  	rr := &RepoRoot{
  1361  		Repo:     repoURL,
  1362  		Root:     mmi.Prefix,
  1363  		IsCustom: true,
  1364  		VCS:      vcs,
  1365  	}
  1366  	return rr, nil
  1367  }
  1368  
  1369  // validateRepoRoot returns an error if repoRoot does not seem to be
  1370  // a valid URL with scheme.
  1371  func validateRepoRoot(repoRoot string) error {
  1372  	url, err := urlpkg.Parse(repoRoot)
  1373  	if err != nil {
  1374  		return err
  1375  	}
  1376  	if url.Scheme == "" {
  1377  		return errors.New("no scheme")
  1378  	}
  1379  	if url.Scheme == "file" {
  1380  		return errors.New("file scheme disallowed")
  1381  	}
  1382  	return nil
  1383  }
  1384  
  1385  var fetchGroup singleflight.Group
  1386  var (
  1387  	fetchCacheMu sync.Mutex
  1388  	fetchCache   = map[string]fetchResult{} // key is metaImportsForPrefix's importPrefix
  1389  )
  1390  
  1391  // metaImportsForPrefix takes a package's root import path as declared in a <meta> tag
  1392  // and returns its HTML discovery URL and the parsed metaImport lines
  1393  // found on the page.
  1394  //
  1395  // The importPath is of the form "golang.org/x/tools".
  1396  // It is an error if no imports are found.
  1397  // url will still be valid if err != nil.
  1398  // The returned url will be of the form "https://golang.org/x/tools?go-get=1"
  1399  func metaImportsForPrefix(importPrefix string, mod ModuleMode, security web.SecurityMode) (*urlpkg.URL, []metaImport, error) {
  1400  	setCache := func(res fetchResult) (fetchResult, error) {
  1401  		fetchCacheMu.Lock()
  1402  		defer fetchCacheMu.Unlock()
  1403  		fetchCache[importPrefix] = res
  1404  		return res, nil
  1405  	}
  1406  
  1407  	resi, _, _ := fetchGroup.Do(importPrefix, func() (resi any, err error) {
  1408  		fetchCacheMu.Lock()
  1409  		if res, ok := fetchCache[importPrefix]; ok {
  1410  			fetchCacheMu.Unlock()
  1411  			return res, nil
  1412  		}
  1413  		fetchCacheMu.Unlock()
  1414  
  1415  		url, err := urlForImportPath(importPrefix)
  1416  		if err != nil {
  1417  			return setCache(fetchResult{err: err})
  1418  		}
  1419  		resp, err := web.Get(security, url)
  1420  		if err != nil {
  1421  			return setCache(fetchResult{url: url, err: fmt.Errorf("fetching %s: %v", importPrefix, err)})
  1422  		}
  1423  		body := resp.Body
  1424  		defer body.Close()
  1425  		imports, err := parseMetaGoImports(body, mod)
  1426  		if len(imports) == 0 {
  1427  			if respErr := resp.Err(); respErr != nil {
  1428  				// If the server's status was not OK, prefer to report that instead of
  1429  				// an XML parse error.
  1430  				return setCache(fetchResult{url: url, err: respErr})
  1431  			}
  1432  		}
  1433  		if err != nil {
  1434  			return setCache(fetchResult{url: url, err: fmt.Errorf("parsing %s: %v", resp.URL, err)})
  1435  		}
  1436  		if len(imports) == 0 {
  1437  			err = fmt.Errorf("fetching %s: no go-import meta tag found in %s", importPrefix, resp.URL)
  1438  		}
  1439  		return setCache(fetchResult{url: url, imports: imports, err: err})
  1440  	})
  1441  	res := resi.(fetchResult)
  1442  	return res.url, res.imports, res.err
  1443  }
  1444  
  1445  type fetchResult struct {
  1446  	url     *urlpkg.URL
  1447  	imports []metaImport
  1448  	err     error
  1449  }
  1450  
  1451  // metaImport represents the parsed <meta name="go-import"
  1452  // content="prefix vcs reporoot" /> tags from HTML files.
  1453  type metaImport struct {
  1454  	Prefix, VCS, RepoRoot string
  1455  }
  1456  
  1457  // An ImportMismatchError is returned where metaImport/s are present
  1458  // but none match our import path.
  1459  type ImportMismatchError struct {
  1460  	importPath string
  1461  	mismatches []string // the meta imports that were discarded for not matching our importPath
  1462  }
  1463  
  1464  func (m ImportMismatchError) Error() string {
  1465  	formattedStrings := make([]string, len(m.mismatches))
  1466  	for i, pre := range m.mismatches {
  1467  		formattedStrings[i] = fmt.Sprintf("meta tag %s did not match import path %s", pre, m.importPath)
  1468  	}
  1469  	return strings.Join(formattedStrings, ", ")
  1470  }
  1471  
  1472  // matchGoImport returns the metaImport from imports matching importPath.
  1473  // An error is returned if there are multiple matches.
  1474  // An ImportMismatchError is returned if none match.
  1475  func matchGoImport(imports []metaImport, importPath string) (metaImport, error) {
  1476  	match := -1
  1477  
  1478  	errImportMismatch := ImportMismatchError{importPath: importPath}
  1479  	for i, im := range imports {
  1480  		if !str.HasPathPrefix(importPath, im.Prefix) {
  1481  			errImportMismatch.mismatches = append(errImportMismatch.mismatches, im.Prefix)
  1482  			continue
  1483  		}
  1484  
  1485  		if match >= 0 {
  1486  			if imports[match].VCS == "mod" && im.VCS != "mod" {
  1487  				// All the mod entries precede all the non-mod entries.
  1488  				// We have a mod entry and don't care about the rest,
  1489  				// matching or not.
  1490  				break
  1491  			}
  1492  			return metaImport{}, fmt.Errorf("multiple meta tags match import path %q", importPath)
  1493  		}
  1494  		match = i
  1495  	}
  1496  
  1497  	if match == -1 {
  1498  		return metaImport{}, errImportMismatch
  1499  	}
  1500  	return imports[match], nil
  1501  }
  1502  
  1503  // expand rewrites s to replace {k} with match[k] for each key k in match.
  1504  func expand(match map[string]string, s string) string {
  1505  	// We want to replace each match exactly once, and the result of expansion
  1506  	// must not depend on the iteration order through the map.
  1507  	// A strings.Replacer has exactly the properties we're looking for.
  1508  	oldNew := make([]string, 0, 2*len(match))
  1509  	for k, v := range match {
  1510  		oldNew = append(oldNew, "{"+k+"}", v)
  1511  	}
  1512  	return strings.NewReplacer(oldNew...).Replace(s)
  1513  }
  1514  
  1515  // vcsPaths defines the meaning of import paths referring to
  1516  // commonly-used VCS hosting sites (github.com/user/dir)
  1517  // and import paths referring to a fully-qualified importPath
  1518  // containing a VCS type (foo.com/repo.git/dir)
  1519  var vcsPaths = []*vcsPath{
  1520  	// GitHub
  1521  	{
  1522  		pathPrefix: "github.com",
  1523  		regexp:     lazyregexp.New(`^(?P<root>github\.com/[\w.\-]+/[\w.\-]+)(/[\w.\-]+)*$`),
  1524  		vcs:        "git",
  1525  		repo:       "https://{root}",
  1526  		check:      noVCSSuffix,
  1527  	},
  1528  
  1529  	// Bitbucket
  1530  	{
  1531  		pathPrefix: "bitbucket.org",
  1532  		regexp:     lazyregexp.New(`^(?P<root>bitbucket\.org/(?P<bitname>[\w.\-]+/[\w.\-]+))(/[\w.\-]+)*$`),
  1533  		vcs:        "git",
  1534  		repo:       "https://{root}",
  1535  		check:      noVCSSuffix,
  1536  	},
  1537  
  1538  	// IBM DevOps Services (JazzHub)
  1539  	{
  1540  		pathPrefix: "hub.jazz.net/git",
  1541  		regexp:     lazyregexp.New(`^(?P<root>hub\.jazz\.net/git/[a-z0-9]+/[\w.\-]+)(/[\w.\-]+)*$`),
  1542  		vcs:        "git",
  1543  		repo:       "https://{root}",
  1544  		check:      noVCSSuffix,
  1545  	},
  1546  
  1547  	// Git at Apache
  1548  	{
  1549  		pathPrefix: "git.apache.org",
  1550  		regexp:     lazyregexp.New(`^(?P<root>git\.apache\.org/[a-z0-9_.\-]+\.git)(/[\w.\-]+)*$`),
  1551  		vcs:        "git",
  1552  		repo:       "https://{root}",
  1553  	},
  1554  
  1555  	// Git at OpenStack
  1556  	{
  1557  		pathPrefix: "git.openstack.org",
  1558  		regexp:     lazyregexp.New(`^(?P<root>git\.openstack\.org/[\w.\-]+/[\w.\-]+)(\.git)?(/[\w.\-]+)*$`),
  1559  		vcs:        "git",
  1560  		repo:       "https://{root}",
  1561  	},
  1562  
  1563  	// chiselapp.com for fossil
  1564  	{
  1565  		pathPrefix: "chiselapp.com",
  1566  		regexp:     lazyregexp.New(`^(?P<root>chiselapp\.com/user/[A-Za-z0-9]+/repository/[\w.\-]+)$`),
  1567  		vcs:        "fossil",
  1568  		repo:       "https://{root}",
  1569  	},
  1570  
  1571  	// General syntax for any server.
  1572  	// Must be last.
  1573  	{
  1574  		regexp:         lazyregexp.New(`(?P<root>(?P<repo>([a-z0-9.\-]+\.)+[a-z0-9.\-]+(:[0-9]+)?(/~?[\w.\-]+)+?)\.(?P<vcs>bzr|fossil|git|hg|svn))(/~?[\w.\-]+)*$`),
  1575  		schemelessRepo: true,
  1576  	},
  1577  }
  1578  
  1579  // vcsPathsAfterDynamic gives additional vcsPaths entries
  1580  // to try after the dynamic HTML check.
  1581  // This gives those sites a chance to introduce <meta> tags
  1582  // as part of a graceful transition away from the hard-coded logic.
  1583  var vcsPathsAfterDynamic = []*vcsPath{
  1584  	// Launchpad. See golang.org/issue/11436.
  1585  	{
  1586  		pathPrefix: "launchpad.net",
  1587  		regexp:     lazyregexp.New(`^(?P<root>launchpad\.net/((?P<project>[\w.\-]+)(?P<series>/[\w.\-]+)?|~[\w.\-]+/(\+junk|[\w.\-]+)/[\w.\-]+))(/[\w.\-]+)*$`),
  1588  		vcs:        "bzr",
  1589  		repo:       "https://{root}",
  1590  		check:      launchpadVCS,
  1591  	},
  1592  }
  1593  
  1594  // noVCSSuffix checks that the repository name does not
  1595  // end in .foo for any version control system foo.
  1596  // The usual culprit is ".git".
  1597  func noVCSSuffix(match map[string]string) error {
  1598  	repo := match["repo"]
  1599  	for _, vcs := range vcsList {
  1600  		if strings.HasSuffix(repo, "."+vcs.Cmd) {
  1601  			return fmt.Errorf("invalid version control suffix in %s path", match["prefix"])
  1602  		}
  1603  	}
  1604  	return nil
  1605  }
  1606  
  1607  // launchpadVCS solves the ambiguity for "lp.net/project/foo". In this case,
  1608  // "foo" could be a series name registered in Launchpad with its own branch,
  1609  // and it could also be the name of a directory within the main project
  1610  // branch one level up.
  1611  func launchpadVCS(match map[string]string) error {
  1612  	if match["project"] == "" || match["series"] == "" {
  1613  		return nil
  1614  	}
  1615  	url := &urlpkg.URL{
  1616  		Scheme: "https",
  1617  		Host:   "code.launchpad.net",
  1618  		Path:   expand(match, "/{project}{series}/.bzr/branch-format"),
  1619  	}
  1620  	_, err := web.GetBytes(url)
  1621  	if err != nil {
  1622  		match["root"] = expand(match, "launchpad.net/{project}")
  1623  		match["repo"] = expand(match, "https://{root}")
  1624  	}
  1625  	return nil
  1626  }
  1627  
  1628  // importError is a copy of load.importError, made to avoid a dependency cycle
  1629  // on cmd/go/internal/load. It just needs to satisfy load.ImportPathError.
  1630  type importError struct {
  1631  	importPath string
  1632  	err        error
  1633  }
  1634  
  1635  func importErrorf(path, format string, args ...any) error {
  1636  	err := &importError{importPath: path, err: fmt.Errorf(format, args...)}
  1637  	if errStr := err.Error(); !strings.Contains(errStr, path) {
  1638  		panic(fmt.Sprintf("path %q not in error %q", path, errStr))
  1639  	}
  1640  	return err
  1641  }
  1642  
  1643  func (e *importError) Error() string {
  1644  	return e.err.Error()
  1645  }
  1646  
  1647  func (e *importError) Unwrap() error {
  1648  	// Don't return e.err directly, since we're only wrapping an error if %w
  1649  	// was passed to ImportErrorf.
  1650  	return errors.Unwrap(e.err)
  1651  }
  1652  
  1653  func (e *importError) ImportPath() string {
  1654  	return e.importPath
  1655  }
  1656  

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