Pretty the help text

This modifies the "docker help" text so that it is no wider than 80 chars
and each description fits on one line. This will also try to use ~ when
possible

Added a test to make sure we don't go over 80 chars again.
Added a test to make sure we use ~

Applied rules/tests to all docker commands - not just main help text

Closes #10214

Signed-off-by: Doug Davis <dug@us.ibm.com>

mflag/flag.go

@@ -86,6 +86,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"runtime"
 	"sort"
 	"strconv"
 	"strings"
@@ -503,6 +504,10 @@ func Set(name, value string) error {
 // otherwise, the default values of all defined flags in the set.
 func (f *FlagSet) PrintDefaults() {
 	writer := tabwriter.NewWriter(f.Out(), 20, 1, 3, ' ', 0)
+	var home string
+	if runtime.GOOS != "windows" {
+		home = os.Getenv("HOME")
+	}
 	f.VisitAll(func(flag *Flag) {
 		format := "  -%s=%s"
 		if _, ok := flag.Value.(*stringValue); ok {
@@ -516,7 +521,13 @@ func (f *FlagSet) PrintDefaults() {
 			}
 		}
 		if len(names) > 0 {
-			fmt.Fprintf(writer, format, strings.Join(names, ", -"), flag.DefValue)
+			val := flag.DefValue
+
+			if home != "" && strings.HasPrefix(val, home) {
+				val = "~" + val[len(home):]
+			}
+
+			fmt.Fprintf(writer, format, strings.Join(names, ", -"), val)
 			for i, line := range strings.Split(flag.Usage, "\n") {
 				if i != 0 {
 					line = "  " + line