go.mod, vendor: update (#3358)

* go.mod, vendor: remove unnecessary dependencies

Commands:
1. go mod tidy
2. go mod vendor

* go.mod, vendor: update cloud.google.com/go

Commands:
1. go get -u cloud.google.com/go
2. go mod tidy
3. go mod vendor

* go.mod, vendor: update cloud.google.com/*

Commands:
1. go get -u cloud.google.com/storage cloud.google.com/logging
2. go mod tidy
3. go mod vendor

* go.mod, .golangci.yml, vendor: update *lint*

Commands:
1. go get -u golang.org/x/tools github.com/golangci/golangci-lint@v1.47.0
2. go mod tidy
3. go mod vendor
4. edit .golangci.yml to suppress new errors (resolved in the same PR later)

* all: fix lint errors

hash.go: copy() recommended by gosimple
parse.go: ent is never nil
verifier.go: signal.Notify() with unbuffered channel is bad. Have no idea why.

* .golangci.yml: adjust godot rules

check-all is deprecated, but still work
if you're hesitating too - I'll remove this commit

7 files changed, 894 insertions, 0 deletions

diff --git a/vendor/github.com/hexops/gotextdiff/span/parse.go b/vendor/github.com/hexops/gotextdiff/span/parse.go
new file mode 100644
index 000000000..aa17c84ec
--- /dev/null
+++ b/vendor/github.com/hexops/gotextdiff/span/parse.go
@@ -0,0 +1,100 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package span
+
+import (
+	"strconv"
+	"strings"
+	"unicode/utf8"
+)
+
+// Parse returns the location represented by the input.
+// Only file paths are accepted, not URIs.
+// The returned span will be normalized, and thus if printed may produce a
+// different string.
+func Parse(input string) Span {
+	// :0:0#0-0:0#0
+	valid := input
+	var hold, offset int
+	hadCol := false
+	suf := rstripSuffix(input)
+	if suf.sep == "#" {
+		offset = suf.num
+		suf = rstripSuffix(suf.remains)
+	}
+	if suf.sep == ":" {
+		valid = suf.remains
+		hold = suf.num
+		hadCol = true
+		suf = rstripSuffix(suf.remains)
+	}
+	switch {
+	case suf.sep == ":":
+		return New(URIFromPath(suf.remains), NewPoint(suf.num, hold, offset), Point{})
+	case suf.sep == "-":
+		// we have a span, fall out of the case to continue
+	default:
+		// separator not valid, rewind to either the : or the start
+		return New(URIFromPath(valid), NewPoint(hold, 0, offset), Point{})
+	}
+	// only the span form can get here
+	// at this point we still don't know what the numbers we have mean
+	// if have not yet seen a : then we might have either a line or a column depending
+	// on whether start has a column or not
+	// we build an end point and will fix it later if needed
+	end := NewPoint(suf.num, hold, offset)
+	hold, offset = 0, 0
+	suf = rstripSuffix(suf.remains)
+	if suf.sep == "#" {
+		offset = suf.num
+		suf = rstripSuffix(suf.remains)
+	}
+	if suf.sep != ":" {
+		// turns out we don't have a span after all, rewind
+		return New(URIFromPath(valid), end, Point{})
+	}
+	valid = suf.remains
+	hold = suf.num
+	suf = rstripSuffix(suf.remains)
+	if suf.sep != ":" {
+		// line#offset only
+		return New(URIFromPath(valid), NewPoint(hold, 0, offset), end)
+	}
+	// we have a column, so if end only had one number, it is also the column
+	if !hadCol {
+		end = NewPoint(suf.num, end.v.Line, end.v.Offset)
+	}
+	return New(URIFromPath(suf.remains), NewPoint(suf.num, hold, offset), end)
+}
+
+type suffix struct {
+	remains string
+	sep     string
+	num     int
+}
+
+func rstripSuffix(input string) suffix {
+	if len(input) == 0 {
+		return suffix{"", "", -1}
+	}
+	remains := input
+	num := -1
+	// first see if we have a number at the end
+	last := strings.LastIndexFunc(remains, func(r rune) bool { return r < '0' || r > '9' })
+	if last >= 0 && last < len(remains)-1 {
+		number, err := strconv.ParseInt(remains[last+1:], 10, 64)
+		if err == nil {
+			num = int(number)
+			remains = remains[:last+1]
+		}
+	}
+	// now see if we have a trailing separator
+	r, w := utf8.DecodeLastRuneInString(remains)
+	if r != ':' && r != '#' && r == '#' {
+		return suffix{input, "", -1}
+	}
+	remains = remains[:len(remains)-w]
+	return suffix{remains, string(r), num}
+}
diff --git a/vendor/github.com/hexops/gotextdiff/span/span.go b/vendor/github.com/hexops/gotextdiff/span/span.go
new file mode 100644
index 000000000..4d2ad0986
--- /dev/null
+++ b/vendor/github.com/hexops/gotextdiff/span/span.go
@@ -0,0 +1,285 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package span contains support for representing with positions and ranges in
+// text files.
+package span
+
+import (
+	"encoding/json"
+	"fmt"
+	"path"
+)
+
+// Span represents a source code range in standardized form.
+type Span struct {
+	v span
+}
+
+// Point represents a single point within a file.
+// In general this should only be used as part of a Span, as on its own it
+// does not carry enough information.
+type Point struct {
+	v point
+}
+
+type span struct {
+	URI   URI   `json:"uri"`
+	Start point `json:"start"`
+	End   point `json:"end"`
+}
+
+type point struct {
+	Line   int `json:"line"`
+	Column int `json:"column"`
+	Offset int `json:"offset"`
+}
+
+// Invalid is a span that reports false from IsValid
+var Invalid = Span{v: span{Start: invalidPoint.v, End: invalidPoint.v}}
+
+var invalidPoint = Point{v: point{Line: 0, Column: 0, Offset: -1}}
+
+// Converter is the interface to an object that can convert between line:column
+// and offset forms for a single file.
+type Converter interface {
+	//ToPosition converts from an offset to a line:column pair.
+	ToPosition(offset int) (int, int, error)
+	//ToOffset converts from a line:column pair to an offset.
+	ToOffset(line, col int) (int, error)
+}
+
+func New(uri URI, start Point, end Point) Span {
+	s := Span{v: span{URI: uri, Start: start.v, End: end.v}}
+	s.v.clean()
+	return s
+}
+
+func NewPoint(line, col, offset int) Point {
+	p := Point{v: point{Line: line, Column: col, Offset: offset}}
+	p.v.clean()
+	return p
+}
+
+func Compare(a, b Span) int {
+	if r := CompareURI(a.URI(), b.URI()); r != 0 {
+		return r
+	}
+	if r := comparePoint(a.v.Start, b.v.Start); r != 0 {
+		return r
+	}
+	return comparePoint(a.v.End, b.v.End)
+}
+
+func ComparePoint(a, b Point) int {
+	return comparePoint(a.v, b.v)
+}
+
+func comparePoint(a, b point) int {
+	if !a.hasPosition() {
+		if a.Offset < b.Offset {
+			return -1
+		}
+		if a.Offset > b.Offset {
+			return 1
+		}
+		return 0
+	}
+	if a.Line < b.Line {
+		return -1
+	}
+	if a.Line > b.Line {
+		return 1
+	}
+	if a.Column < b.Column {
+		return -1
+	}
+	if a.Column > b.Column {
+		return 1
+	}
+	return 0
+}
+
+func (s Span) HasPosition() bool             { return s.v.Start.hasPosition() }
+func (s Span) HasOffset() bool               { return s.v.Start.hasOffset() }
+func (s Span) IsValid() bool                 { return s.v.Start.isValid() }
+func (s Span) IsPoint() bool                 { return s.v.Start == s.v.End }
+func (s Span) URI() URI                      { return s.v.URI }
+func (s Span) Start() Point                  { return Point{s.v.Start} }
+func (s Span) End() Point                    { return Point{s.v.End} }
+func (s *Span) MarshalJSON() ([]byte, error) { return json.Marshal(&s.v) }
+func (s *Span) UnmarshalJSON(b []byte) error { return json.Unmarshal(b, &s.v) }
+
+func (p Point) HasPosition() bool             { return p.v.hasPosition() }
+func (p Point) HasOffset() bool               { return p.v.hasOffset() }
+func (p Point) IsValid() bool                 { return p.v.isValid() }
+func (p *Point) MarshalJSON() ([]byte, error) { return json.Marshal(&p.v) }
+func (p *Point) UnmarshalJSON(b []byte) error { return json.Unmarshal(b, &p.v) }
+func (p Point) Line() int {
+	if !p.v.hasPosition() {
+		panic(fmt.Errorf("position not set in %v", p.v))
+	}
+	return p.v.Line
+}
+func (p Point) Column() int {
+	if !p.v.hasPosition() {
+		panic(fmt.Errorf("position not set in %v", p.v))
+	}
+	return p.v.Column
+}
+func (p Point) Offset() int {
+	if !p.v.hasOffset() {
+		panic(fmt.Errorf("offset not set in %v", p.v))
+	}
+	return p.v.Offset
+}
+
+func (p point) hasPosition() bool { return p.Line > 0 }
+func (p point) hasOffset() bool   { return p.Offset >= 0 }
+func (p point) isValid() bool     { return p.hasPosition() || p.hasOffset() }
+func (p point) isZero() bool {
+	return (p.Line == 1 && p.Column == 1) || (!p.hasPosition() && p.Offset == 0)
+}
+
+func (s *span) clean() {
+	//this presumes the points are already clean
+	if !s.End.isValid() || (s.End == point{}) {
+		s.End = s.Start
+	}
+}
+
+func (p *point) clean() {
+	if p.Line < 0 {
+		p.Line = 0
+	}
+	if p.Column <= 0 {
+		if p.Line > 0 {
+			p.Column = 1
+		} else {
+			p.Column = 0
+		}
+	}
+	if p.Offset == 0 && (p.Line > 1 || p.Column > 1) {
+		p.Offset = -1
+	}
+}
+
+// Format implements fmt.Formatter to print the Location in a standard form.
+// The format produced is one that can be read back in using Parse.
+func (s Span) Format(f fmt.State, c rune) {
+	fullForm := f.Flag('+')
+	preferOffset := f.Flag('#')
+	// we should always have a uri, simplify if it is file format
+	//TODO: make sure the end of the uri is unambiguous
+	uri := string(s.v.URI)
+	if c == 'f' {
+		uri = path.Base(uri)
+	} else if !fullForm {
+		uri = s.v.URI.Filename()
+	}
+	fmt.Fprint(f, uri)
+	if !s.IsValid() || (!fullForm && s.v.Start.isZero() && s.v.End.isZero()) {
+		return
+	}
+	// see which bits of start to write
+	printOffset := s.HasOffset() && (fullForm || preferOffset || !s.HasPosition())
+	printLine := s.HasPosition() && (fullForm || !printOffset)
+	printColumn := printLine && (fullForm || (s.v.Start.Column > 1 || s.v.End.Column > 1))
+	fmt.Fprint(f, ":")
+	if printLine {
+		fmt.Fprintf(f, "%d", s.v.Start.Line)
+	}
+	if printColumn {
+		fmt.Fprintf(f, ":%d", s.v.Start.Column)
+	}
+	if printOffset {
+		fmt.Fprintf(f, "#%d", s.v.Start.Offset)
+	}
+	// start is written, do we need end?
+	if s.IsPoint() {
+		return
+	}
+	// we don't print the line if it did not change
+	printLine = fullForm || (printLine && s.v.End.Line > s.v.Start.Line)
+	fmt.Fprint(f, "-")
+	if printLine {
+		fmt.Fprintf(f, "%d", s.v.End.Line)
+	}
+	if printColumn {
+		if printLine {
+			fmt.Fprint(f, ":")
+		}
+		fmt.Fprintf(f, "%d", s.v.End.Column)
+	}
+	if printOffset {
+		fmt.Fprintf(f, "#%d", s.v.End.Offset)
+	}
+}
+
+func (s Span) WithPosition(c Converter) (Span, error) {
+	if err := s.update(c, true, false); err != nil {
+		return Span{}, err
+	}
+	return s, nil
+}
+
+func (s Span) WithOffset(c Converter) (Span, error) {
+	if err := s.update(c, false, true); err != nil {
+		return Span{}, err
+	}
+	return s, nil
+}
+
+func (s Span) WithAll(c Converter) (Span, error) {
+	if err := s.update(c, true, true); err != nil {
+		return Span{}, err
+	}
+	return s, nil
+}
+
+func (s *Span) update(c Converter, withPos, withOffset bool) error {
+	if !s.IsValid() {
+		return fmt.Errorf("cannot add information to an invalid span")
+	}
+	if withPos && !s.HasPosition() {
+		if err := s.v.Start.updatePosition(c); err != nil {
+			return err
+		}
+		if s.v.End.Offset == s.v.Start.Offset {
+			s.v.End = s.v.Start
+		} else if err := s.v.End.updatePosition(c); err != nil {
+			return err
+		}
+	}
+	if withOffset && (!s.HasOffset() || (s.v.End.hasPosition() && !s.v.End.hasOffset())) {
+		if err := s.v.Start.updateOffset(c); err != nil {
+			return err
+		}
+		if s.v.End.Line == s.v.Start.Line && s.v.End.Column == s.v.Start.Column {
+			s.v.End.Offset = s.v.Start.Offset
+		} else if err := s.v.End.updateOffset(c); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (p *point) updatePosition(c Converter) error {
+	line, col, err := c.ToPosition(p.Offset)
+	if err != nil {
+		return err
+	}
+	p.Line = line
+	p.Column = col
+	return nil
+}
+
+func (p *point) updateOffset(c Converter) error {
+	offset, err := c.ToOffset(p.Line, p.Column)
+	if err != nil {
+		return err
+	}
+	p.Offset = offset
+	return nil
+}
diff --git a/vendor/github.com/hexops/gotextdiff/span/token.go b/vendor/github.com/hexops/gotextdiff/span/token.go
new file mode 100644
index 000000000..6f8b9b570
--- /dev/null
+++ b/vendor/github.com/hexops/gotextdiff/span/token.go
@@ -0,0 +1,194 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package span
+
+import (
+	"fmt"
+	"go/token"
+)
+
+// Range represents a source code range in token.Pos form.
+// It also carries the FileSet that produced the positions, so that it is
+// self contained.
+type Range struct {
+	FileSet   *token.FileSet
+	Start     token.Pos
+	End       token.Pos
+	Converter Converter
+}
+
+type FileConverter struct {
+	file *token.File
+}
+
+// TokenConverter is a Converter backed by a token file set and file.
+// It uses the file set methods to work out the conversions, which
+// makes it fast and does not require the file contents.
+type TokenConverter struct {
+	FileConverter
+	fset *token.FileSet
+}
+
+// NewRange creates a new Range from a FileSet and two positions.
+// To represent a point pass a 0 as the end pos.
+func NewRange(fset *token.FileSet, start, end token.Pos) Range {
+	return Range{
+		FileSet: fset,
+		Start:   start,
+		End:     end,
+	}
+}
+
+// NewTokenConverter returns an implementation of Converter backed by a
+// token.File.
+func NewTokenConverter(fset *token.FileSet, f *token.File) *TokenConverter {
+	return &TokenConverter{fset: fset, FileConverter: FileConverter{file: f}}
+}
+
+// NewContentConverter returns an implementation of Converter for the
+// given file content.
+func NewContentConverter(filename string, content []byte) *TokenConverter {
+	fset := token.NewFileSet()
+	f := fset.AddFile(filename, -1, len(content))
+	f.SetLinesForContent(content)
+	return NewTokenConverter(fset, f)
+}
+
+// IsPoint returns true if the range represents a single point.
+func (r Range) IsPoint() bool {
+	return r.Start == r.End
+}
+
+// Span converts a Range to a Span that represents the Range.
+// It will fill in all the members of the Span, calculating the line and column
+// information.
+func (r Range) Span() (Span, error) {
+	if !r.Start.IsValid() {
+		return Span{}, fmt.Errorf("start pos is not valid")
+	}
+	f := r.FileSet.File(r.Start)
+	if f == nil {
+		return Span{}, fmt.Errorf("file not found in FileSet")
+	}
+	return FileSpan(f, r.Converter, r.Start, r.End)
+}
+
+// FileSpan returns a span within tok, using converter to translate between
+// offsets and positions.
+func FileSpan(tok *token.File, converter Converter, start, end token.Pos) (Span, error) {
+	var s Span
+	var err error
+	var startFilename string
+	startFilename, s.v.Start.Line, s.v.Start.Column, err = position(tok, start)
+	if err != nil {
+		return Span{}, err
+	}
+	s.v.URI = URIFromPath(startFilename)
+	if end.IsValid() {
+		var endFilename string
+		endFilename, s.v.End.Line, s.v.End.Column, err = position(tok, end)
+		if err != nil {
+			return Span{}, err
+		}
+		// In the presence of line directives, a single File can have sections from
+		// multiple file names.
+		if endFilename != startFilename {
+			return Span{}, fmt.Errorf("span begins in file %q but ends in %q", startFilename, endFilename)
+		}
+	}
+	s.v.Start.clean()
+	s.v.End.clean()
+	s.v.clean()
+	if converter != nil {
+		return s.WithOffset(converter)
+	}
+	if startFilename != tok.Name() {
+		return Span{}, fmt.Errorf("must supply Converter for file %q containing lines from %q", tok.Name(), startFilename)
+	}
+	return s.WithOffset(&FileConverter{tok})
+}
+
+func position(f *token.File, pos token.Pos) (string, int, int, error) {
+	off, err := offset(f, pos)
+	if err != nil {
+		return "", 0, 0, err
+	}
+	return positionFromOffset(f, off)
+}
+
+func positionFromOffset(f *token.File, offset int) (string, int, int, error) {
+	if offset > f.Size() {
+		return "", 0, 0, fmt.Errorf("offset %v is past the end of the file %v", offset, f.Size())
+	}
+	pos := f.Pos(offset)
+	p := f.Position(pos)
+	// TODO(golang/go#41029): Consider returning line, column instead of line+1, 1 if
+	// the file's last character is not a newline.
+	if offset == f.Size() {
+		return p.Filename, p.Line + 1, 1, nil
+	}
+	return p.Filename, p.Line, p.Column, nil
+}
+
+// offset is a copy of the Offset function in go/token, but with the adjustment
+// that it does not panic on invalid positions.
+func offset(f *token.File, pos token.Pos) (int, error) {
+	if int(pos) < f.Base() || int(pos) > f.Base()+f.Size() {
+		return 0, fmt.Errorf("invalid pos")
+	}
+	return int(pos) - f.Base(), nil
+}
+
+// Range converts a Span to a Range that represents the Span for the supplied
+// File.
+func (s Span) Range(converter *TokenConverter) (Range, error) {
+	s, err := s.WithOffset(converter)
+	if err != nil {
+		return Range{}, err
+	}
+	// go/token will panic if the offset is larger than the file's size,
+	// so check here to avoid panicking.
+	if s.Start().Offset() > converter.file.Size() {
+		return Range{}, fmt.Errorf("start offset %v is past the end of the file %v", s.Start(), converter.file.Size())
+	}
+	if s.End().Offset() > converter.file.Size() {
+		return Range{}, fmt.Errorf("end offset %v is past the end of the file %v", s.End(), converter.file.Size())
+	}
+	return Range{
+		FileSet:   converter.fset,
+		Start:     converter.file.Pos(s.Start().Offset()),
+		End:       converter.file.Pos(s.End().Offset()),
+		Converter: converter,
+	}, nil
+}
+
+func (l *FileConverter) ToPosition(offset int) (int, int, error) {
+	_, line, col, err := positionFromOffset(l.file, offset)
+	return line, col, err
+}
+
+func (l *FileConverter) ToOffset(line, col int) (int, error) {
+	if line < 0 {
+		return -1, fmt.Errorf("line is not valid")
+	}
+	lineMax := l.file.LineCount() + 1
+	if line > lineMax {
+		return -1, fmt.Errorf("line is beyond end of file %v", lineMax)
+	} else if line == lineMax {
+		if col > 1 {
+			return -1, fmt.Errorf("column is beyond end of file")
+		}
+		// at the end of the file, allowing for a trailing eol
+		return l.file.Size(), nil
+	}
+	pos := lineStart(l.file, line)
+	if !pos.IsValid() {
+		return -1, fmt.Errorf("line is not in file")
+	}
+	// we assume that column is in bytes here, and that the first byte of a
+	// line is at column 1
+	pos += token.Pos(col - 1)
+	return offset(l.file, pos)
+}
diff --git a/vendor/github.com/hexops/gotextdiff/span/token111.go b/vendor/github.com/hexops/gotextdiff/span/token111.go
new file mode 100644
index 000000000..bf7a5406b
--- /dev/null
+++ b/vendor/github.com/hexops/gotextdiff/span/token111.go
@@ -0,0 +1,39 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !go1.12
+
+package span
+
+import (
+	"go/token"
+)
+
+// lineStart is the pre-Go 1.12 version of (*token.File).LineStart. For Go
+// versions <= 1.11, we borrow logic from the analysisutil package.
+// TODO(rstambler): Delete this file when we no longer support Go 1.11.
+func lineStart(f *token.File, line int) token.Pos {
+	// Use binary search to find the start offset of this line.
+
+	min := 0        // inclusive
+	max := f.Size() // exclusive
+	for {
+		offset := (min + max) / 2
+		pos := f.Pos(offset)
+		posn := f.Position(pos)
+		if posn.Line == line {
+			return pos - (token.Pos(posn.Column) - 1)
+		}
+
+		if min+1 >= max {
+			return token.NoPos
+		}
+
+		if posn.Line < line {
+			min = offset
+		} else {
+			max = offset
+		}
+	}
+}
diff --git a/vendor/github.com/hexops/gotextdiff/span/token112.go b/vendor/github.com/hexops/gotextdiff/span/token112.go
new file mode 100644
index 000000000..017aec9c1
--- /dev/null
+++ b/vendor/github.com/hexops/gotextdiff/span/token112.go
@@ -0,0 +1,16 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.12
+
+package span
+
+import (
+	"go/token"
+)
+
+// TODO(rstambler): Delete this file when we no longer support Go 1.11.
+func lineStart(f *token.File, line int) token.Pos {
+	return f.LineStart(line)
+}
diff --git a/vendor/github.com/hexops/gotextdiff/span/uri.go b/vendor/github.com/hexops/gotextdiff/span/uri.go
new file mode 100644
index 000000000..250492135
--- /dev/null
+++ b/vendor/github.com/hexops/gotextdiff/span/uri.go
@@ -0,0 +1,169 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package span
+
+import (
+	"fmt"
+	"net/url"
+	"os"
+	"path"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"unicode"
+)
+
+const fileScheme = "file"
+
+// URI represents the full URI for a file.
+type URI string
+
+func (uri URI) IsFile() bool {
+	return strings.HasPrefix(string(uri), "file://")
+}
+
+// Filename returns the file path for the given URI.
+// It is an error to call this on a URI that is not a valid filename.
+func (uri URI) Filename() string {
+	filename, err := filename(uri)
+	if err != nil {
+		panic(err)
+	}
+	return filepath.FromSlash(filename)
+}
+
+func filename(uri URI) (string, error) {
+	if uri == "" {
+		return "", nil
+	}
+	u, err := url.ParseRequestURI(string(uri))
+	if err != nil {
+		return "", err
+	}
+	if u.Scheme != fileScheme {
+		return "", fmt.Errorf("only file URIs are supported, got %q from %q", u.Scheme, uri)
+	}
+	// If the URI is a Windows URI, we trim the leading "/" and lowercase
+	// the drive letter, which will never be case sensitive.
+	if isWindowsDriveURIPath(u.Path) {
+		u.Path = strings.ToUpper(string(u.Path[1])) + u.Path[2:]
+	}
+	return u.Path, nil
+}
+
+func URIFromURI(s string) URI {
+	if !strings.HasPrefix(s, "file://") {
+		return URI(s)
+	}
+
+	if !strings.HasPrefix(s, "file:///") {
+		// VS Code sends URLs with only two slashes, which are invalid. golang/go#39789.
+		s = "file:///" + s[len("file://"):]
+	}
+	// Even though the input is a URI, it may not be in canonical form. VS Code
+	// in particular over-escapes :, @, etc. Unescape and re-encode to canonicalize.
+	path, err := url.PathUnescape(s[len("file://"):])
+	if err != nil {
+		panic(err)
+	}
+
+	// File URIs from Windows may have lowercase drive letters.
+	// Since drive letters are guaranteed to be case insensitive,
+	// we change them to uppercase to remain consistent.
+	// For example, file:///c:/x/y/z becomes file:///C:/x/y/z.
+	if isWindowsDriveURIPath(path) {
+		path = path[:1] + strings.ToUpper(string(path[1])) + path[2:]
+	}
+	u := url.URL{Scheme: fileScheme, Path: path}
+	return URI(u.String())
+}
+
+func CompareURI(a, b URI) int {
+	if equalURI(a, b) {
+		return 0
+	}
+	if a < b {
+		return -1
+	}
+	return 1
+}
+
+func equalURI(a, b URI) bool {
+	if a == b {
+		return true
+	}
+	// If we have the same URI basename, we may still have the same file URIs.
+	if !strings.EqualFold(path.Base(string(a)), path.Base(string(b))) {
+		return false
+	}
+	fa, err := filename(a)
+	if err != nil {
+		return false
+	}
+	fb, err := filename(b)
+	if err != nil {
+		return false
+	}
+	// Stat the files to check if they are equal.
+	infoa, err := os.Stat(filepath.FromSlash(fa))
+	if err != nil {
+		return false
+	}
+	infob, err := os.Stat(filepath.FromSlash(fb))
+	if err != nil {
+		return false
+	}
+	return os.SameFile(infoa, infob)
+}
+
+// URIFromPath returns a span URI for the supplied file path.
+// It will always have the file scheme.
+func URIFromPath(path string) URI {
+	if path == "" {
+		return ""
+	}
+	// Handle standard library paths that contain the literal "$GOROOT".
+	// TODO(rstambler): The go/packages API should allow one to determine a user's $GOROOT.
+	const prefix = "$GOROOT"
+	if len(path) >= len(prefix) && strings.EqualFold(prefix, path[:len(prefix)]) {
+		suffix := path[len(prefix):]
+		path = runtime.GOROOT() + suffix
+	}
+	if !isWindowsDrivePath(path) {
+		if abs, err := filepath.Abs(path); err == nil {
+			path = abs
+		}
+	}
+	// Check the file path again, in case it became absolute.
+	if isWindowsDrivePath(path) {
+		path = "/" + strings.ToUpper(string(path[0])) + path[1:]
+	}
+	path = filepath.ToSlash(path)
+	u := url.URL{
+		Scheme: fileScheme,
+		Path:   path,
+	}
+	return URI(u.String())
+}
+
+// isWindowsDrivePath returns true if the file path is of the form used by
+// Windows. We check if the path begins with a drive letter, followed by a ":".
+// For example: C:/x/y/z.
+func isWindowsDrivePath(path string) bool {
+	if len(path) < 3 {
+		return false
+	}
+	return unicode.IsLetter(rune(path[0])) && path[1] == ':'
+}
+
+// isWindowsDriveURI returns true if the file URI is of the format used by
+// Windows URIs. The url.Parse package does not specially handle Windows paths
+// (see golang/go#6027), so we check if the URI path has a drive prefix (e.g. "/C:").
+func isWindowsDriveURIPath(uri string) bool {
+	if len(uri) < 4 {
+		return false
+	}
+	return uri[0] == '/' && unicode.IsLetter(rune(uri[1])) && uri[2] == ':'
+}
diff --git a/vendor/github.com/hexops/gotextdiff/span/utf16.go b/vendor/github.com/hexops/gotextdiff/span/utf16.go
new file mode 100644
index 000000000..f06a2468b
--- /dev/null
+++ b/vendor/github.com/hexops/gotextdiff/span/utf16.go
@@ -0,0 +1,91 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package span
+
+import (
+	"fmt"
+	"unicode/utf16"
+	"unicode/utf8"
+)
+
+// ToUTF16Column calculates the utf16 column expressed by the point given the
+// supplied file contents.
+// This is used to convert from the native (always in bytes) column
+// representation and the utf16 counts used by some editors.
+func ToUTF16Column(p Point, content []byte) (int, error) {
+	if !p.HasPosition() {
+		return -1, fmt.Errorf("ToUTF16Column: point is missing position")
+	}
+	if !p.HasOffset() {
+		return -1, fmt.Errorf("ToUTF16Column: point is missing offset")
+	}
+	offset := p.Offset()      // 0-based
+	colZero := p.Column() - 1 // 0-based
+	if colZero == 0 {
+		// 0-based column 0, so it must be chr 1
+		return 1, nil
+	} else if colZero < 0 {
+		return -1, fmt.Errorf("ToUTF16Column: column is invalid (%v)", colZero)
+	}
+	// work out the offset at the start of the line using the column
+	lineOffset := offset - colZero
+	if lineOffset < 0 || offset > len(content) {
+		return -1, fmt.Errorf("ToUTF16Column: offsets %v-%v outside file contents (%v)", lineOffset, offset, len(content))
+	}
+	// Use the offset to pick out the line start.
+	// This cannot panic: offset > len(content) and lineOffset < offset.
+	start := content[lineOffset:]
+
+	// Now, truncate down to the supplied column.
+	start = start[:colZero]
+
+	// and count the number of utf16 characters
+	// in theory we could do this by hand more efficiently...
+	return len(utf16.Encode([]rune(string(start)))) + 1, nil
+}
+
+// FromUTF16Column advances the point by the utf16 character offset given the
+// supplied line contents.
+// This is used to convert from the utf16 counts used by some editors to the
+// native (always in bytes) column representation.
+func FromUTF16Column(p Point, chr int, content []byte) (Point, error) {
+	if !p.HasOffset() {
+		return Point{}, fmt.Errorf("FromUTF16Column: point is missing offset")
+	}
+	// if chr is 1 then no adjustment needed
+	if chr <= 1 {
+		return p, nil
+	}
+	if p.Offset() >= len(content) {
+		return p, fmt.Errorf("FromUTF16Column: offset (%v) greater than length of content (%v)", p.Offset(), len(content))
+	}
+	remains := content[p.Offset():]
+	// scan forward the specified number of characters
+	for count := 1; count < chr; count++ {
+		if len(remains) <= 0 {
+			return Point{}, fmt.Errorf("FromUTF16Column: chr goes beyond the content")
+		}
+		r, w := utf8.DecodeRune(remains)
+		if r == '\n' {
+			// Per the LSP spec:
+			//
+			// > If the character value is greater than the line length it
+			// > defaults back to the line length.
+			break
+		}
+		remains = remains[w:]
+		if r >= 0x10000 {
+			// a two point rune
+			count++
+			// if we finished in a two point rune, do not advance past the first
+			if count >= chr {
+				break
+			}
+		}
+		p.v.Column += w
+		p.v.Offset += w
+	}
+	return p, nil
+}