switch to use gliderlabs/ssh for builtin server (#7250)

resolves git conflicts from #3896 (credit to @belak, in case github doesn't keep original author during squash)

Co-Authored-By: Matti Ranta <techknowlogick@gitea.io>

vendor/github.com/anmitsu/go-shlex/.gitignore

@@ -0,0 +1 @@
+shlex.test

vendor/github.com/anmitsu/go-shlex/LICENSE

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+Copyright (c) anmitsu <anmitsu.s@gmail.com>
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

vendor/github.com/anmitsu/go-shlex/README.md

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+# go-shlex
+
+go-shlex is a library to make a lexical analyzer like Unix shell for
+Go.
+
+## Install
+
+    go get -u "github.com/anmitsu/go-shlex"
+
+## Usage
+
+```go
+package main
+
+import (
+    "fmt"
+    "log"
+
+    "github.com/anmitsu/go-shlex"
+)
+
+func main() {
+    cmd := `cp -Rdp "file name" 'file name2' dir\ name`
+    words, err := shlex.Split(cmd, true)
+    if err != nil {
+        log.Fatal(err)
+    }
+
+    for _, w := range words {
+        fmt.Println(w)
+    }
+}
+```
+
+## Documentation
+
+http://godoc.org/github.com/anmitsu/go-shlex
+

vendor/github.com/anmitsu/go-shlex/shlex.go

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+// Package shlex provides a simple lexical analysis like Unix shell.
+package shlex
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"strings"
+	"unicode"
+)
+
+var (
+	ErrNoClosing = errors.New("No closing quotation")
+	ErrNoEscaped = errors.New("No escaped character")
+)
+
+// Tokenizer is the interface that classifies a token according to
+// words, whitespaces, quotations, escapes and escaped quotations.
+type Tokenizer interface {
+	IsWord(rune) bool
+	IsWhitespace(rune) bool
+	IsQuote(rune) bool
+	IsEscape(rune) bool
+	IsEscapedQuote(rune) bool
+}
+
+// DefaultTokenizer implements a simple tokenizer like Unix shell.
+type DefaultTokenizer struct{}
+
+func (t *DefaultTokenizer) IsWord(r rune) bool {
+	return r == '_' || unicode.IsLetter(r) || unicode.IsNumber(r)
+}
+func (t *DefaultTokenizer) IsQuote(r rune) bool {
+	switch r {
+	case '\'', '"':
+		return true
+	default:
+		return false
+	}
+}
+func (t *DefaultTokenizer) IsWhitespace(r rune) bool {
+	return unicode.IsSpace(r)
+}
+func (t *DefaultTokenizer) IsEscape(r rune) bool {
+	return r == '\\'
+}
+func (t *DefaultTokenizer) IsEscapedQuote(r rune) bool {
+	return r == '"'
+}
+
+// Lexer represents a lexical analyzer.
+type Lexer struct {
+	reader          *bufio.Reader
+	tokenizer       Tokenizer
+	posix           bool
+	whitespacesplit bool
+}
+
+// NewLexer creates a new Lexer reading from io.Reader.  This Lexer
+// has a DefaultTokenizer according to posix and whitespacesplit
+// rules.
+func NewLexer(r io.Reader, posix, whitespacesplit bool) *Lexer {
+	return &Lexer{
+		reader:          bufio.NewReader(r),
+		tokenizer:       &DefaultTokenizer{},
+		posix:           posix,
+		whitespacesplit: whitespacesplit,
+	}
+}
+
+// NewLexerString creates a new Lexer reading from a string.  This
+// Lexer has a DefaultTokenizer according to posix and whitespacesplit
+// rules.
+func NewLexerString(s string, posix, whitespacesplit bool) *Lexer {
+	return NewLexer(strings.NewReader(s), posix, whitespacesplit)
+}
+
+// Split splits a string according to posix or non-posix rules.
+func Split(s string, posix bool) ([]string, error) {
+	return NewLexerString(s, posix, true).Split()
+}
+
+// SetTokenizer sets a Tokenizer.
+func (l *Lexer) SetTokenizer(t Tokenizer) {
+	l.tokenizer = t
+}
+
+func (l *Lexer) Split() ([]string, error) {
+	result := make([]string, 0)
+	for {
+		token, err := l.readToken()
+		if token != "" {
+			result = append(result, token)
+		}
+
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return result, err
+		}
+	}
+	return result, nil
+}
+
+func (l *Lexer) readToken() (string, error) {
+	t := l.tokenizer
+	token := ""
+	quoted := false
+	state := ' '
+	escapedstate := ' '
+scanning:
+	for {
+		next, _, err := l.reader.ReadRune()
+		if err != nil {
+			if t.IsQuote(state) {
+				return token, ErrNoClosing
+			} else if t.IsEscape(state) {
+				return token, ErrNoEscaped
+			}
+			return token, err
+		}
+
+		switch {
+		case t.IsWhitespace(state):
+			switch {
+			case t.IsWhitespace(next):
+				break scanning
+			case l.posix && t.IsEscape(next):
+				escapedstate = 'a'
+				state = next
+			case t.IsWord(next):
+				token += string(next)
+				state = 'a'
+			case t.IsQuote(next):
+				if !l.posix {
+					token += string(next)
+				}
+				state = next
+			default:
+				token = string(next)
+				if l.whitespacesplit {
+					state = 'a'
+				} else if token != "" || (l.posix && quoted) {
+					break scanning
+				}
+			}
+		case t.IsQuote(state):
+			quoted = true
+			switch {
+			case next == state:
+				if !l.posix {
+					token += string(next)
+					break scanning
+				} else {
+					state = 'a'
+				}
+			case l.posix && t.IsEscape(next) && t.IsEscapedQuote(state):
+				escapedstate = state
+				state = next
+			default:
+				token += string(next)
+			}
+		case t.IsEscape(state):
+			if t.IsQuote(escapedstate) && next != state && next != escapedstate {
+				token += string(state)
+			}
+			token += string(next)
+			state = escapedstate
+		case t.IsWord(state):
+			switch {
+			case t.IsWhitespace(next):
+				if token != "" || (l.posix && quoted) {
+					break scanning
+				}
+			case l.posix && t.IsQuote(next):
+				state = next
+			case l.posix && t.IsEscape(next):
+				escapedstate = 'a'
+				state = next
+			case t.IsWord(next) || t.IsQuote(next):
+				token += string(next)
+			default:
+				if l.whitespacesplit {
+					token += string(next)
+				} else if token != "" {
+					l.reader.UnreadRune()
+					break scanning
+				}
+			}
+		}
+	}
+	return token, nil
+}