diff --git a/src/cmd/go/internal/modfetch/coderepo.go b/src/cmd/go/internal/modfetch/coderepo.go
index 79da010..2206c7c 100644
--- a/src/cmd/go/internal/modfetch/coderepo.go
+++ b/src/cmd/go/internal/modfetch/coderepo.go
@@ -298,16 +298,13 @@
 // If statVers is a valid module version, it is used for the Version field.
 // Otherwise, the Version is derived from the passed-in info and recent tags.
 func (r *codeRepo) convert(info *codehost.RevInfo, statVers string) (*RevInfo, error) {
-	info2 := &RevInfo{
-		Name:  info.Name,
-		Short: info.Short,
-		Time:  info.Time,
-	}
-
 	// If this is a plain tag (no dir/ prefix)
 	// and the module path is unversioned,
 	// and if the underlying file tree has no go.mod,
 	// then allow using the tag with a +incompatible suffix.
+	//
+	// (If the version is +incompatible, then the go.mod file must not exist:
+	// +incompatible is not an ongoing opt-out from semantic import versioning.)
 	var canUseIncompatible func() bool
 	canUseIncompatible = func() bool {
 		var ok bool
@@ -321,19 +318,12 @@
 		return ok
 	}
 
-	invalidf := func(format string, args ...any) error {
-		return &module.ModuleError{
-			Path: r.modPath,
-			Err: &module.InvalidVersionError{
-				Version: info2.Version,
-				Err:     fmt.Errorf(format, args...),
-			},
-		}
-	}
-
-	// checkGoMod verifies that the go.mod file for the module exists or does not
-	// exist as required by info2.Version and the module path represented by r.
-	checkGoMod := func() (*RevInfo, error) {
+	// checkCanonical verifies that the canonical version v is compatible with the
+	// module path represented by r, adding a "+incompatible" suffix if needed.
+	//
+	// If statVers is also canonical, checkCanonical also verifies that v is
+	// either statVers or statVers with the added "+incompatible" suffix.
+	checkCanonical := func(v string) (*RevInfo, error) {
 		// If r.codeDir is non-empty, then the go.mod file must exist: the module
 		// author — not the module consumer, — gets to decide how to carve up the repo
 		// into modules.
@@ -344,73 +334,91 @@
 		// r.findDir verifies both of these conditions. Execute it now so that
 		// r.Stat will correctly return a notExistError if the go.mod location or
 		// declared module path doesn't match.
-		_, _, _, err := r.findDir(info2.Version)
+		_, _, _, err := r.findDir(v)
 		if err != nil {
 			// TODO: It would be nice to return an error like "not a module".
 			// Right now we return "missing go.mod", which is a little confusing.
 			return nil, &module.ModuleError{
 				Path: r.modPath,
 				Err: &module.InvalidVersionError{
-					Version: info2.Version,
+					Version: v,
 					Err:     notExistError{err: err},
 				},
 			}
 		}
 
-		// If the version is +incompatible, then the go.mod file must not exist:
-		// +incompatible is not an ongoing opt-out from semantic import versioning.
-		if strings.HasSuffix(info2.Version, "+incompatible") {
-			if !canUseIncompatible() {
-				if r.pathMajor != "" {
-					return nil, invalidf("+incompatible suffix not allowed: module path includes a major version suffix, so major version must match")
-				} else {
-					return nil, invalidf("+incompatible suffix not allowed: module contains a go.mod file, so semantic import versioning is required")
-				}
-			}
-
-			if err := module.CheckPathMajor(strings.TrimSuffix(info2.Version, "+incompatible"), r.pathMajor); err == nil {
-				return nil, invalidf("+incompatible suffix not allowed: major version %s is compatible", semver.Major(info2.Version))
+		invalidf := func(format string, args ...any) error {
+			return &module.ModuleError{
+				Path: r.modPath,
+				Err: &module.InvalidVersionError{
+					Version: v,
+					Err:     fmt.Errorf(format, args...),
+				},
 			}
 		}
 
-		return info2, nil
+		// Add the +incompatible suffix if needed or requested explicitly, and
+		// verify that its presence or absence is appropriate for this version
+		// (which depends on whether it has an explicit go.mod file).
+
+		if v == strings.TrimSuffix(statVers, "+incompatible") {
+			v = statVers
+		}
+		base := strings.TrimSuffix(v, "+incompatible")
+		var errIncompatible error
+		if !module.MatchPathMajor(base, r.pathMajor) {
+			if canUseIncompatible() {
+				v = base + "+incompatible"
+			} else {
+				if r.pathMajor != "" {
+					errIncompatible = invalidf("module path includes a major version suffix, so major version must match")
+				} else {
+					errIncompatible = invalidf("module contains a go.mod file, so module path must match major version (%q)", path.Join(r.pathPrefix, semver.Major(v)))
+				}
+			}
+		} else if strings.HasSuffix(v, "+incompatible") {
+			errIncompatible = invalidf("+incompatible suffix not allowed: major version %s is compatible", semver.Major(v))
+		}
+
+		if statVers != "" && statVers == module.CanonicalVersion(statVers) {
+			// Since the caller-requested version is canonical, it would be very
+			// confusing to resolve it to anything but itself, possibly with a
+			// "+incompatible" suffix. Error out explicitly.
+			if statBase := strings.TrimSuffix(statVers, "+incompatible"); statBase != base {
+				return nil, &module.ModuleError{
+					Path: r.modPath,
+					Err: &module.InvalidVersionError{
+						Version: statVers,
+						Err:     fmt.Errorf("resolves to version %v (%s is not a tag)", v, statBase),
+					},
+				}
+			}
+		}
+
+		if errIncompatible != nil {
+			return nil, errIncompatible
+		}
+
+		return &RevInfo{
+			Name:    info.Name,
+			Short:   info.Short,
+			Time:    info.Time,
+			Version: v,
+		}, nil
 	}
 
 	// Determine version.
-	//
-	// If statVers is canonical, then the original call was repo.Stat(statVers).
-	// Since the version is canonical, we must not resolve it to anything but
-	// itself, possibly with a '+incompatible' annotation: we do not need to do
-	// the work required to look for an arbitrary pseudo-version.
-	if statVers != "" && statVers == module.CanonicalVersion(statVers) {
-		info2.Version = statVers
 
-		if module.IsPseudoVersion(info2.Version) {
-			if err := r.validatePseudoVersion(info, info2.Version); err != nil {
-				return nil, err
-			}
-			return checkGoMod()
+	if module.IsPseudoVersion(statVers) {
+		if err := r.validatePseudoVersion(info, statVers); err != nil {
+			return nil, err
 		}
-
-		if err := module.CheckPathMajor(info2.Version, r.pathMajor); err != nil {
-			if canUseIncompatible() {
-				info2.Version += "+incompatible"
-				return checkGoMod()
-			} else {
-				if vErr, ok := err.(*module.InvalidVersionError); ok {
-					// We're going to describe why the version is invalid in more detail,
-					// so strip out the existing “invalid version” wrapper.
-					err = vErr.Err
-				}
-				return nil, invalidf("module contains a go.mod file, so major version must be compatible: %v", err)
-			}
-		}
-
-		return checkGoMod()
+		return checkCanonical(statVers)
 	}
 
-	// statVers is empty or non-canonical, so we need to resolve it to a canonical
-	// version or pseudo-version.
+	// statVers is not a pseudo-version, so we need to either resolve it to a
+	// canonical version or verify that it is already a canonical tag
+	// (not a branch).
 
 	// Derive or verify a version from a code repo tag.
 	// Tag must have a prefix matching codeDir.
@@ -441,71 +449,62 @@
 		if v == "" || !strings.HasPrefix(trimmed, v) {
 			return "", false // Invalid or incomplete version (just vX or vX.Y).
 		}
-		if isRetracted(v) {
-			return "", false
-		}
 		if v == trimmed {
 			tagIsCanonical = true
 		}
-
-		if err := module.CheckPathMajor(v, r.pathMajor); err != nil {
-			if canUseIncompatible() {
-				return v + "+incompatible", tagIsCanonical
-			}
-			return "", false
-		}
-
 		return v, tagIsCanonical
 	}
 
 	// If the VCS gave us a valid version, use that.
 	if v, tagIsCanonical := tagToVersion(info.Version); tagIsCanonical {
-		info2.Version = v
-		return checkGoMod()
+		if info, err := checkCanonical(v); err == nil {
+			return info, err
+		}
 	}
 
 	// Look through the tags on the revision for either a usable canonical version
 	// or an appropriate base for a pseudo-version.
-	var pseudoBase string
+	var (
+		highestCanonical string
+		pseudoBase       string
+	)
 	for _, pathTag := range info.Tags {
 		v, tagIsCanonical := tagToVersion(pathTag)
-		if tagIsCanonical {
-			if statVers != "" && semver.Compare(v, statVers) == 0 {
-				// The user requested a non-canonical version, but the tag for the
-				// canonical equivalent refers to the same revision. Use it.
-				info2.Version = v
-				return checkGoMod()
+		if statVers != "" && semver.Compare(v, statVers) == 0 {
+			// The tag is equivalent to the version requested by the user.
+			if tagIsCanonical {
+				// This tag is the canonical form of the requested version,
+				// not some other form with extra build metadata.
+				// Use this tag so that the resolved version will match exactly.
+				// (If it isn't actually allowed, we'll error out in checkCanonical.)
+				return checkCanonical(v)
 			} else {
-				// Save the highest canonical tag for the revision. If we don't find a
-				// better match, we'll use it as the canonical version.
+				// The user explicitly requested something equivalent to this tag. We
+				// can't use the version from the tag directly: since the tag is not
+				// canonical, it could be ambiguous. For example, tags v0.0.1+a and
+				// v0.0.1+b might both exist and refer to different revisions.
 				//
-				// NOTE: Do not replace this with semver.Max. Despite the name,
-				// semver.Max *also* canonicalizes its arguments, which uses
-				// semver.Canonical instead of module.CanonicalVersion and thereby
-				// strips our "+incompatible" suffix.
-				if semver.Compare(info2.Version, v) < 0 {
-					info2.Version = v
-				}
+				// The tag is otherwise valid for the module, so we can at least use it as
+				// the base of an unambiguous pseudo-version.
+				//
+				// If multiple tags match, tagToVersion will canonicalize them to the same
+				// base version.
+				pseudoBase = v
 			}
-		} else if v != "" && semver.Compare(v, statVers) == 0 {
-			// The user explicitly requested something equivalent to this tag. We
-			// can't use the version from the tag directly: since the tag is not
-			// canonical, it could be ambiguous. For example, tags v0.0.1+a and
-			// v0.0.1+b might both exist and refer to different revisions.
-			//
-			// The tag is otherwise valid for the module, so we can at least use it as
-			// the base of an unambiguous pseudo-version.
-			//
-			// If multiple tags match, tagToVersion will canonicalize them to the same
-			// base version.
-			pseudoBase = v
+		}
+		// Save the highest non-retracted canonical tag for the revision.
+		// If we don't find a better match, we'll use it as the canonical version.
+		if tagIsCanonical && semver.Compare(highestCanonical, v) < 0 && !isRetracted(v) {
+			if module.MatchPathMajor(v, r.pathMajor) || canUseIncompatible() {
+				highestCanonical = v
+			}
 		}
 	}
 
-	// If we found any canonical tag for the revision, return it.
+	// If we found a valid canonical tag for the revision, return it.
 	// Even if we found a good pseudo-version base, a canonical version is better.
-	if info2.Version != "" {
-		return checkGoMod()
+	if highestCanonical != "" {
+		return checkCanonical(highestCanonical)
 	}
 
 	// Find the highest tagged version in the revision's history, subject to
@@ -528,11 +527,10 @@
 				tag, _ = r.code.RecentTag(info.Name, tagPrefix, allowedMajor("v0"))
 			}
 		}
-		pseudoBase, _ = tagToVersion(tag) // empty if the tag is invalid
+		pseudoBase, _ = tagToVersion(tag)
 	}
 
-	info2.Version = module.PseudoVersion(r.pseudoMajor, pseudoBase, info.Time, info.Short)
-	return checkGoMod()
+	return checkCanonical(module.PseudoVersion(r.pseudoMajor, pseudoBase, info.Time, info.Short))
 }
 
 // validatePseudoVersion checks that version has a major version compatible with
@@ -556,10 +554,6 @@
 		}
 	}()
 
-	if err := module.CheckPathMajor(version, r.pathMajor); err != nil {
-		return err
-	}
-
 	rev, err := module.PseudoVersionRev(version)
 	if err != nil {
 		return err
diff --git a/src/cmd/go/internal/modfetch/coderepo_test.go b/src/cmd/go/internal/modfetch/coderepo_test.go
index 02e399f..d98ea87 100644
--- a/src/cmd/go/internal/modfetch/coderepo_test.go
+++ b/src/cmd/go/internal/modfetch/coderepo_test.go
@@ -418,171 +418,204 @@
 		zipSum:      "h1:JItBZ+gwA5WvtZEGEbuDL4lUttGtLrs53lmdurq3bOg=",
 		zipFileHash: "9ea9ae1673cffcc44b7fdd3cc89953d68c102449b46c982dbf085e4f2e394da5",
 	},
+	{
+		// Git branch with a semver name, +incompatible version, and no go.mod file.
+		vcs:  "git",
+		path: "vcs-test.golang.org/go/mod/gitrepo1",
+		rev:  "v2.3.4+incompatible",
+		err:  `resolves to version v2.0.1+incompatible (v2.3.4 is not a tag)`,
+	},
+	{
+		// Git branch with a semver name, matching go.mod file, and compatible version.
+		vcs:  "git",
+		path: "vcs-test.golang.org/git/semver-branch.git",
+		rev:  "v1.0.0",
+		err:  `resolves to version v0.1.1-0.20220202191944-09c4d8f6938c (v1.0.0 is not a tag)`,
+	},
+	{
+		// Git branch with a semver name, matching go.mod file, and disallowed +incompatible version.
+		// The version/tag mismatch takes precedence over the +incompatible mismatched.
+		vcs:  "git",
+		path: "vcs-test.golang.org/git/semver-branch.git",
+		rev:  "v2.0.0+incompatible",
+		err:  `resolves to version v0.1.0 (v2.0.0 is not a tag)`,
+	},
+	{
+		// Git branch with a semver name, matching go.mod file, and mismatched version.
+		// The version/tag mismatch takes precedence over the +incompatible mismatched.
+		vcs:  "git",
+		path: "vcs-test.golang.org/git/semver-branch.git",
+		rev:  "v2.0.0",
+		err:  `resolves to version v0.1.0 (v2.0.0 is not a tag)`,
+	},
+	{
+		// v3.0.0-devel is the same as tag v4.0.0-beta.1, but v4.0.0-beta.1 would
+		// not be allowed because it is incompatible and a go.mod file exists.
+		// The error message should refer to a valid pseudo-version, not the
+		// unusable semver tag.
+		vcs:  "git",
+		path: "vcs-test.golang.org/git/semver-branch.git",
+		rev:  "v3.0.0-devel",
+		err:  `resolves to version v0.1.1-0.20220203155313-d59622f6e4d7 (v3.0.0-devel is not a tag)`,
+	},
 }
 
 func TestCodeRepo(t *testing.T) {
 	testenv.MustHaveExternalNetwork(t)
+	tmpdir := t.TempDir()
 
-	tmpdir, err := os.MkdirTemp("", "modfetch-test-")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(tmpdir)
+	for _, tt := range codeRepoTests {
+		f := func(tt codeRepoTest) func(t *testing.T) {
+			return func(t *testing.T) {
+				t.Parallel()
+				if tt.vcs != "mod" {
+					testenv.MustHaveExecPath(t, tt.vcs)
+				}
 
-	t.Run("parallel", func(t *testing.T) {
-		for _, tt := range codeRepoTests {
-			f := func(tt codeRepoTest) func(t *testing.T) {
-				return func(t *testing.T) {
-					t.Parallel()
-					if tt.vcs != "mod" {
-						testenv.MustHaveExecPath(t, tt.vcs)
-					}
+				repo := Lookup("direct", tt.path)
 
-					repo := Lookup("direct", tt.path)
+				if tt.mpath == "" {
+					tt.mpath = tt.path
+				}
+				if mpath := repo.ModulePath(); mpath != tt.mpath {
+					t.Errorf("repo.ModulePath() = %q, want %q", mpath, tt.mpath)
+				}
 
-					if tt.mpath == "" {
-						tt.mpath = tt.path
-					}
-					if mpath := repo.ModulePath(); mpath != tt.mpath {
-						t.Errorf("repo.ModulePath() = %q, want %q", mpath, tt.mpath)
-					}
-
-					info, err := repo.Stat(tt.rev)
-					if err != nil {
-						if tt.err != "" {
-							if !strings.Contains(err.Error(), tt.err) {
-								t.Fatalf("repoStat(%q): %v, wanted %q", tt.rev, err, tt.err)
-							}
-							return
-						}
-						t.Fatalf("repo.Stat(%q): %v", tt.rev, err)
-					}
+				info, err := repo.Stat(tt.rev)
+				if err != nil {
 					if tt.err != "" {
-						t.Errorf("repo.Stat(%q): success, wanted error", tt.rev)
+						if !strings.Contains(err.Error(), tt.err) {
+							t.Fatalf("repoStat(%q): %v, wanted %q", tt.rev, err, tt.err)
+						}
+						return
 					}
-					if info.Version != tt.version {
-						t.Errorf("info.Version = %q, want %q", info.Version, tt.version)
-					}
-					if info.Name != tt.name {
-						t.Errorf("info.Name = %q, want %q", info.Name, tt.name)
-					}
-					if info.Short != tt.short {
-						t.Errorf("info.Short = %q, want %q", info.Short, tt.short)
-					}
-					if !info.Time.Equal(tt.time) {
-						t.Errorf("info.Time = %v, want %v", info.Time, tt.time)
-					}
+					t.Fatalf("repo.Stat(%q): %v", tt.rev, err)
+				}
+				if tt.err != "" {
+					t.Errorf("repo.Stat(%q): success, wanted error", tt.rev)
+				}
+				if info.Version != tt.version {
+					t.Errorf("info.Version = %q, want %q", info.Version, tt.version)
+				}
+				if info.Name != tt.name {
+					t.Errorf("info.Name = %q, want %q", info.Name, tt.name)
+				}
+				if info.Short != tt.short {
+					t.Errorf("info.Short = %q, want %q", info.Short, tt.short)
+				}
+				if !info.Time.Equal(tt.time) {
+					t.Errorf("info.Time = %v, want %v", info.Time, tt.time)
+				}
 
-					if tt.gomod != "" || tt.gomodErr != "" {
-						data, err := repo.GoMod(tt.version)
-						if err != nil && tt.gomodErr == "" {
-							t.Errorf("repo.GoMod(%q): %v", tt.version, err)
-						} else if err != nil && tt.gomodErr != "" {
-							if err.Error() != tt.gomodErr {
-								t.Errorf("repo.GoMod(%q): %v, want %q", tt.version, err, tt.gomodErr)
-							}
-						} else if tt.gomodErr != "" {
-							t.Errorf("repo.GoMod(%q) = %q, want error %q", tt.version, data, tt.gomodErr)
-						} else if string(data) != tt.gomod {
-							t.Errorf("repo.GoMod(%q) = %q, want %q", tt.version, data, tt.gomod)
+				if tt.gomod != "" || tt.gomodErr != "" {
+					data, err := repo.GoMod(tt.version)
+					if err != nil && tt.gomodErr == "" {
+						t.Errorf("repo.GoMod(%q): %v", tt.version, err)
+					} else if err != nil && tt.gomodErr != "" {
+						if err.Error() != tt.gomodErr {
+							t.Errorf("repo.GoMod(%q): %v, want %q", tt.version, err, tt.gomodErr)
 						}
-					}
-
-					needHash := !testing.Short() && (tt.zipFileHash != "" || tt.zipSum != "")
-					if tt.zip != nil || tt.zipErr != "" || needHash {
-						f, err := os.CreateTemp(tmpdir, tt.version+".zip.")
-						if err != nil {
-							t.Fatalf("os.CreateTemp: %v", err)
-						}
-						zipfile := f.Name()
-						defer func() {
-							f.Close()
-							os.Remove(zipfile)
-						}()
-
-						var w io.Writer
-						var h hash.Hash
-						if needHash {
-							h = sha256.New()
-							w = io.MultiWriter(f, h)
-						} else {
-							w = f
-						}
-						err = repo.Zip(w, tt.version)
-						f.Close()
-						if err != nil {
-							if tt.zipErr != "" {
-								if err.Error() == tt.zipErr {
-									return
-								}
-								t.Fatalf("repo.Zip(%q): %v, want error %q", tt.version, err, tt.zipErr)
-							}
-							t.Fatalf("repo.Zip(%q): %v", tt.version, err)
-						}
-						if tt.zipErr != "" {
-							t.Errorf("repo.Zip(%q): success, want error %q", tt.version, tt.zipErr)
-						}
-
-						if tt.zip != nil {
-							prefix := tt.path + "@" + tt.version + "/"
-							z, err := zip.OpenReader(zipfile)
-							if err != nil {
-								t.Fatalf("open zip %s: %v", zipfile, err)
-							}
-							var names []string
-							for _, file := range z.File {
-								if !strings.HasPrefix(file.Name, prefix) {
-									t.Errorf("zip entry %v does not start with prefix %v", file.Name, prefix)
-									continue
-								}
-								names = append(names, file.Name[len(prefix):])
-							}
-							z.Close()
-							if !reflect.DeepEqual(names, tt.zip) {
-								t.Fatalf("zip = %v\nwant %v\n", names, tt.zip)
-							}
-						}
-
-						if needHash {
-							sum, err := dirhash.HashZip(zipfile, dirhash.Hash1)
-							if err != nil {
-								t.Errorf("repo.Zip(%q): %v", tt.version, err)
-							} else if sum != tt.zipSum {
-								t.Errorf("repo.Zip(%q): got file with sum %q, want %q", tt.version, sum, tt.zipSum)
-							} else if zipFileHash := hex.EncodeToString(h.Sum(nil)); zipFileHash != tt.zipFileHash {
-								t.Errorf("repo.Zip(%q): got file with hash %q, want %q (but content has correct sum)", tt.version, zipFileHash, tt.zipFileHash)
-							}
-						}
+					} else if tt.gomodErr != "" {
+						t.Errorf("repo.GoMod(%q) = %q, want error %q", tt.version, data, tt.gomodErr)
+					} else if string(data) != tt.gomod {
+						t.Errorf("repo.GoMod(%q) = %q, want %q", tt.version, data, tt.gomod)
 					}
 				}
-			}
-			t.Run(strings.ReplaceAll(tt.path, "/", "_")+"/"+tt.rev, f(tt))
-			if strings.HasPrefix(tt.path, vgotest1git) {
-				for vcs, alt := range altVgotests {
-					altTest := tt
-					altTest.vcs = vcs
-					altTest.path = alt + strings.TrimPrefix(altTest.path, vgotest1git)
-					if strings.HasPrefix(altTest.mpath, vgotest1git) {
-						altTest.mpath = alt + strings.TrimPrefix(altTest.mpath, vgotest1git)
+
+				needHash := !testing.Short() && (tt.zipFileHash != "" || tt.zipSum != "")
+				if tt.zip != nil || tt.zipErr != "" || needHash {
+					f, err := os.CreateTemp(tmpdir, tt.version+".zip.")
+					if err != nil {
+						t.Fatalf("os.CreateTemp: %v", err)
 					}
-					var m map[string]string
-					if alt == vgotest1hg {
-						m = hgmap
+					zipfile := f.Name()
+					defer func() {
+						f.Close()
+						os.Remove(zipfile)
+					}()
+
+					var w io.Writer
+					var h hash.Hash
+					if needHash {
+						h = sha256.New()
+						w = io.MultiWriter(f, h)
+					} else {
+						w = f
 					}
-					altTest.version = remap(altTest.version, m)
-					altTest.name = remap(altTest.name, m)
-					altTest.short = remap(altTest.short, m)
-					altTest.rev = remap(altTest.rev, m)
-					altTest.err = remap(altTest.err, m)
-					altTest.gomodErr = remap(altTest.gomodErr, m)
-					altTest.zipErr = remap(altTest.zipErr, m)
-					altTest.zipSum = ""
-					altTest.zipFileHash = ""
-					t.Run(strings.ReplaceAll(altTest.path, "/", "_")+"/"+altTest.rev, f(altTest))
+					err = repo.Zip(w, tt.version)
+					f.Close()
+					if err != nil {
+						if tt.zipErr != "" {
+							if err.Error() == tt.zipErr {
+								return
+							}
+							t.Fatalf("repo.Zip(%q): %v, want error %q", tt.version, err, tt.zipErr)
+						}
+						t.Fatalf("repo.Zip(%q): %v", tt.version, err)
+					}
+					if tt.zipErr != "" {
+						t.Errorf("repo.Zip(%q): success, want error %q", tt.version, tt.zipErr)
+					}
+
+					if tt.zip != nil {
+						prefix := tt.path + "@" + tt.version + "/"
+						z, err := zip.OpenReader(zipfile)
+						if err != nil {
+							t.Fatalf("open zip %s: %v", zipfile, err)
+						}
+						var names []string
+						for _, file := range z.File {
+							if !strings.HasPrefix(file.Name, prefix) {
+								t.Errorf("zip entry %v does not start with prefix %v", file.Name, prefix)
+								continue
+							}
+							names = append(names, file.Name[len(prefix):])
+						}
+						z.Close()
+						if !reflect.DeepEqual(names, tt.zip) {
+							t.Fatalf("zip = %v\nwant %v\n", names, tt.zip)
+						}
+					}
+
+					if needHash {
+						sum, err := dirhash.HashZip(zipfile, dirhash.Hash1)
+						if err != nil {
+							t.Errorf("repo.Zip(%q): %v", tt.version, err)
+						} else if sum != tt.zipSum {
+							t.Errorf("repo.Zip(%q): got file with sum %q, want %q", tt.version, sum, tt.zipSum)
+						} else if zipFileHash := hex.EncodeToString(h.Sum(nil)); zipFileHash != tt.zipFileHash {
+							t.Errorf("repo.Zip(%q): got file with hash %q, want %q (but content has correct sum)", tt.version, zipFileHash, tt.zipFileHash)
+						}
+					}
 				}
 			}
 		}
-	})
+		t.Run(strings.ReplaceAll(tt.path, "/", "_")+"/"+tt.rev, f(tt))
+		if strings.HasPrefix(tt.path, vgotest1git) {
+			for vcs, alt := range altVgotests {
+				altTest := tt
+				altTest.vcs = vcs
+				altTest.path = alt + strings.TrimPrefix(altTest.path, vgotest1git)
+				if strings.HasPrefix(altTest.mpath, vgotest1git) {
+					altTest.mpath = alt + strings.TrimPrefix(altTest.mpath, vgotest1git)
+				}
+				var m map[string]string
+				if alt == vgotest1hg {
+					m = hgmap
+				}
+				altTest.version = remap(altTest.version, m)
+				altTest.name = remap(altTest.name, m)
+				altTest.short = remap(altTest.short, m)
+				altTest.rev = remap(altTest.rev, m)
+				altTest.err = remap(altTest.err, m)
+				altTest.gomodErr = remap(altTest.gomodErr, m)
+				altTest.zipErr = remap(altTest.zipErr, m)
+				altTest.zipSum = ""
+				altTest.zipFileHash = ""
+				t.Run(strings.ReplaceAll(altTest.path, "/", "_")+"/"+altTest.rev, f(altTest))
+			}
+		}
+	}
 }
 
 var hgmap = map[string]string{
diff --git a/src/cmd/go/testdata/script/mod_invalid_version.txt b/src/cmd/go/testdata/script/mod_invalid_version.txt
index 428b8aa..8385b08d 100644
--- a/src/cmd/go/testdata/script/mod_invalid_version.txt
+++ b/src/cmd/go/testdata/script/mod_invalid_version.txt
@@ -194,10 +194,10 @@
 go mod edit -require github.com/pierrec/lz4@v2.0.9-0.20190209155647-9a39efadad3d+incompatible
 cd outside
 ! go list -m github.com/pierrec/lz4
-stderr 'go: example.com@v0.0.0 requires\n\tgithub.com/pierrec/lz4@v2.0.9-0.20190209155647-9a39efadad3d\+incompatible: invalid version: \+incompatible suffix not allowed: module contains a go.mod file, so semantic import versioning is required'
+stderr '^go: example.com@v0.0.0 requires\n\tgithub.com/pierrec/lz4@v2.0.9-0.20190209155647-9a39efadad3d\+incompatible: invalid version: module contains a go.mod file, so module path must match major version \("github.com/pierrec/lz4/v2"\)$'
 cd ..
 ! go list -m github.com/pierrec/lz4
-stderr 'github.com/pierrec/lz4@v2.0.9-0.20190209155647-9a39efadad3d\+incompatible: invalid version: \+incompatible suffix not allowed: module contains a go.mod file, so semantic import versioning is required'
+stderr '^go: github.com/pierrec/lz4@v2.0.9-0.20190209155647-9a39efadad3d\+incompatible: invalid version: module contains a go.mod file, so module path must match major version \("github.com/pierrec/lz4/v2"\)$'
 
 # A +incompatible pseudo-version is valid for a revision of the module
 # that lacks a go.mod file.
@@ -222,7 +222,7 @@
 # not resolve to a pseudo-version with a different major version.
 cp go.mod.orig go.mod
 ! go get github.com/pierrec/lz4@v2.0.8
-stderr 'go: github.com/pierrec/lz4@v2.0.8: invalid version: module contains a go.mod file, so major version must be compatible: should be v0 or v1, not v2'
+stderr 'go: github.com/pierrec/lz4@v2.0.8: invalid version: module contains a go.mod file, so module path must match major version \("github.com/pierrec/lz4/v2"\)$'
 
 # An invalid +incompatible suffix for a canonical version should error out,
 # not resolve to a pseudo-version.
@@ -233,10 +233,10 @@
 go mod edit -require github.com/pierrec/lz4@v2.0.8+incompatible
 cd outside
 ! go list -m github.com/pierrec/lz4
-stderr 'github.com/pierrec/lz4@v2.0.8\+incompatible: invalid version: \+incompatible suffix not allowed: module contains a go.mod file, so semantic import versioning is required'
+stderr '^go: github.com/pierrec/lz4@v2.0.8\+incompatible: invalid version: module contains a go.mod file, so module path must match major version \("github.com/pierrec/lz4/v2"\)$'
 cd ..
 ! go list -m github.com/pierrec/lz4
-stderr 'github.com/pierrec/lz4@v2.0.8\+incompatible: invalid version: \+incompatible suffix not allowed: module contains a go.mod file, so semantic import versioning is required'
+stderr '^go: github.com/pierrec/lz4@v2.0.8\+incompatible: invalid version: module contains a go.mod file, so module path must match major version \("github.com/pierrec/lz4/v2"\)$'
 
 -- go.mod.orig --
 module example.com