Add node provider interfaace (#526)

This starts the work of having a `NodeProvider` which is responsible for
providing node details.
It splits the responsibilities of node management off to a new
controller.

The primary change here is to add the framework pieces for node
management and move the VK CLI to use this new controller.

It also adds support for node leases where available. This can be
enabled via the command line (disabled by default), but may fall back if
we find that leaess aren't supported on the cluster.

vendor/gotest.tools/internal/format/diff.go

@@ -0,0 +1,161 @@
+package format
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+	"unicode"
+
+	"gotest.tools/internal/difflib"
+)
+
+const (
+	contextLines = 2
+)
+
+// DiffConfig for a unified diff
+type DiffConfig struct {
+	A    string
+	B    string
+	From string
+	To   string
+}
+
+// UnifiedDiff is a modified version of difflib.WriteUnifiedDiff with better
+// support for showing the whitespace differences.
+func UnifiedDiff(conf DiffConfig) string {
+	a := strings.SplitAfter(conf.A, "\n")
+	b := strings.SplitAfter(conf.B, "\n")
+	groups := difflib.NewMatcher(a, b).GetGroupedOpCodes(contextLines)
+	if len(groups) == 0 {
+		return ""
+	}
+
+	buf := new(bytes.Buffer)
+	writeFormat := func(format string, args ...interface{}) {
+		buf.WriteString(fmt.Sprintf(format, args...))
+	}
+	writeLine := func(prefix string, s string) {
+		buf.WriteString(prefix + s)
+	}
+	if hasWhitespaceDiffLines(groups, a, b) {
+		writeLine = visibleWhitespaceLine(writeLine)
+	}
+	formatHeader(writeFormat, conf)
+	for _, group := range groups {
+		formatRangeLine(writeFormat, group)
+		for _, opCode := range group {
+			in, out := a[opCode.I1:opCode.I2], b[opCode.J1:opCode.J2]
+			switch opCode.Tag {
+			case 'e':
+				formatLines(writeLine, " ", in)
+			case 'r':
+				formatLines(writeLine, "-", in)
+				formatLines(writeLine, "+", out)
+			case 'd':
+				formatLines(writeLine, "-", in)
+			case 'i':
+				formatLines(writeLine, "+", out)
+			}
+		}
+	}
+	return buf.String()
+}
+
+// hasWhitespaceDiffLines returns true if any diff groups is only different
+// because of whitespace characters.
+func hasWhitespaceDiffLines(groups [][]difflib.OpCode, a, b []string) bool {
+	for _, group := range groups {
+		in, out := new(bytes.Buffer), new(bytes.Buffer)
+		for _, opCode := range group {
+			if opCode.Tag == 'e' {
+				continue
+			}
+			for _, line := range a[opCode.I1:opCode.I2] {
+				in.WriteString(line)
+			}
+			for _, line := range b[opCode.J1:opCode.J2] {
+				out.WriteString(line)
+			}
+		}
+		if removeWhitespace(in.String()) == removeWhitespace(out.String()) {
+			return true
+		}
+	}
+	return false
+}
+
+func removeWhitespace(s string) string {
+	var result []rune
+	for _, r := range s {
+		if !unicode.IsSpace(r) {
+			result = append(result, r)
+		}
+	}
+	return string(result)
+}
+
+func visibleWhitespaceLine(ws func(string, string)) func(string, string) {
+	mapToVisibleSpace := func(r rune) rune {
+		switch r {
+		case '\n':
+		case ' ':
+			return '·'
+		case '\t':
+			return '▷'
+		case '\v':
+			return '▽'
+		case '\r':
+			return '↵'
+		case '\f':
+			return '↓'
+		default:
+			if unicode.IsSpace(r) {
+				return '<27>'
+			}
+		}
+		return r
+	}
+	return func(prefix, s string) {
+		ws(prefix, strings.Map(mapToVisibleSpace, s))
+	}
+}
+
+func formatHeader(wf func(string, ...interface{}), conf DiffConfig) {
+	if conf.From != "" || conf.To != "" {
+		wf("--- %s\n", conf.From)
+		wf("+++ %s\n", conf.To)
+	}
+}
+
+func formatRangeLine(wf func(string, ...interface{}), group []difflib.OpCode) {
+	first, last := group[0], group[len(group)-1]
+	range1 := formatRangeUnified(first.I1, last.I2)
+	range2 := formatRangeUnified(first.J1, last.J2)
+	wf("@@ -%s +%s @@\n", range1, range2)
+}
+
+// Convert range to the "ed" format
+func formatRangeUnified(start, stop int) string {
+	// Per the diff spec at http://www.unix.org/single_unix_specification/
+	beginning := start + 1 // lines start numbering with one
+	length := stop - start
+	if length == 1 {
+		return fmt.Sprintf("%d", beginning)
+	}
+	if length == 0 {
+		beginning-- // empty ranges begin at line just before the range
+	}
+	return fmt.Sprintf("%d,%d", beginning, length)
+}
+
+func formatLines(writeLine func(string, string), prefix string, lines []string) {
+	for _, line := range lines {
+		writeLine(prefix, line)
+	}
+	// Add a newline if the last line is missing one so that the diff displays
+	// properly.
+	if !strings.HasSuffix(lines[len(lines)-1], "\n") {
+		writeLine("", "\n")
+	}
+}

vendor/gotest.tools/internal/format/format.go

@@ -0,0 +1,27 @@
+package format // import "gotest.tools/internal/format"
+
+import "fmt"
+
+// Message accepts a msgAndArgs varargs and formats it using fmt.Sprintf
+func Message(msgAndArgs ...interface{}) string {
+	switch len(msgAndArgs) {
+	case 0:
+		return ""
+	case 1:
+		return fmt.Sprintf("%v", msgAndArgs[0])
+	default:
+		return fmt.Sprintf(msgAndArgs[0].(string), msgAndArgs[1:]...)
+	}
+}
+
+// WithCustomMessage accepts one or two messages and formats them appropriately
+func WithCustomMessage(source string, msgAndArgs ...interface{}) string {
+	custom := Message(msgAndArgs...)
+	switch {
+	case custom == "":
+		return source
+	case source == "":
+		return custom
+	}
+	return fmt.Sprintf("%s: %s", source, custom)
+}