Add gitea-vet (#10948)

* Add copyright

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Add gitea-vet and fix non-compliance

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Combine tools.go into build.go and clean up

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Remove extra GO111MODULE=on

Signed-off-by: jolheiser <john.olheiser@gmail.com>

vendor/golang.org/x/tools/go/analysis/validate.go

@@ -0,0 +1,97 @@
+package analysis
+
+import (
+	"fmt"
+	"reflect"
+	"unicode"
+)
+
+// Validate reports an error if any of the analyzers are misconfigured.
+// Checks include:
+// that the name is a valid identifier;
+// that the Requires graph is acyclic;
+// that analyzer fact types are unique;
+// that each fact type is a pointer.
+func Validate(analyzers []*Analyzer) error {
+	// Map each fact type to its sole generating analyzer.
+	factTypes := make(map[reflect.Type]*Analyzer)
+
+	// Traverse the Requires graph, depth first.
+	const (
+		white = iota
+		grey
+		black
+		finished
+	)
+	color := make(map[*Analyzer]uint8)
+	var visit func(a *Analyzer) error
+	visit = func(a *Analyzer) error {
+		if a == nil {
+			return fmt.Errorf("nil *Analyzer")
+		}
+		if color[a] == white {
+			color[a] = grey
+
+			// names
+			if !validIdent(a.Name) {
+				return fmt.Errorf("invalid analyzer name %q", a)
+			}
+
+			if a.Doc == "" {
+				return fmt.Errorf("analyzer %q is undocumented", a)
+			}
+
+			// fact types
+			for _, f := range a.FactTypes {
+				if f == nil {
+					return fmt.Errorf("analyzer %s has nil FactType", a)
+				}
+				t := reflect.TypeOf(f)
+				if prev := factTypes[t]; prev != nil {
+					return fmt.Errorf("fact type %s registered by two analyzers: %v, %v",
+						t, a, prev)
+				}
+				if t.Kind() != reflect.Ptr {
+					return fmt.Errorf("%s: fact type %s is not a pointer", a, t)
+				}
+				factTypes[t] = a
+			}
+
+			// recursion
+			for i, req := range a.Requires {
+				if err := visit(req); err != nil {
+					return fmt.Errorf("%s.Requires[%d]: %v", a.Name, i, err)
+				}
+			}
+			color[a] = black
+		}
+
+		return nil
+	}
+	for _, a := range analyzers {
+		if err := visit(a); err != nil {
+			return err
+		}
+	}
+
+	// Reject duplicates among analyzers.
+	// Precondition:  color[a] == black.
+	// Postcondition: color[a] == finished.
+	for _, a := range analyzers {
+		if color[a] == finished {
+			return fmt.Errorf("duplicate analyzer: %s", a.Name)
+		}
+		color[a] = finished
+	}
+
+	return nil
+}
+
+func validIdent(name string) bool {
+	for i, r := range name {
+		if !(r == '_' || unicode.IsLetter(r) || i > 0 && unicode.IsDigit(r)) {
+			return false
+		}
+	}
+	return name != ""
+}