Fix regression in handling flag-values starting with hyphen

Fix for a regression between v1.22.1 and v1.22.2, where
flag values starting with a hyphen would be parsed as a flag:

    runc update test_update --memory-swap -1
    Incorrect Usage: flag provided but not defined: -1

This problem was caused by `reorderArgs()` not properly checking
if the next arg in the list was a value for the flag (and not
the next flag);

Before this patch:

    args before reordering: --opt,--opt-value,arg1
    args after reordering:  --opt,arg1,--opt-value
    args before reordering: --opt,--opt-value,arg1,arg2
    args after reordering:  --opt,arg1,--opt-value,arg2
    args before reordering: arg1,--opt,--opt-value,arg2
    args after reordering:  --opt,arg2,arg1,--opt-value

After this patch is applied:

    args before reordering: --opt,--opt-value,arg1
    args after reordering:  --opt,--opt-value,arg1
    args before reordering: --opt,--opt-value,arg1,arg2
    args after reordering:  --opt,--opt-value,arg1,arg2
    args before reordering: arg1,--opt,--opt-value,arg2
    args after reordering:  --opt,--opt-value,arg1,arg2

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

command.go

@@ -235,7 +235,7 @@ func reorderArgs(commandFlags []Flag, args []string) []string {
 			break
 
 			// checks if this arg is a value that should be re-ordered next to its associated flag
-		} else if nextIndexMayContainValue && !strings.HasPrefix(arg, "-") {
+		} else if nextIndexMayContainValue && !argIsFlag(commandFlags, arg) {
 			nextIndexMayContainValue = false
 			reorderedArgs = append(reorderedArgs, arg)
 

command_test.go

@@ -114,6 +114,72 @@ func TestParseAndRunShortOpts(t *testing.T) {
 	}
 }
 
+// test-case for https://github.com/urfave/cli/issues/1092
+func TestParseAndRunHyphenValues(t *testing.T) {
+	cases := []struct {
+		testArgs     []string
+		expectedArgs []string
+		expectedOpt string
+	}{
+		{[]string{"foo", "test", "arg1"}, []string{"arg1"}, ""},
+		{[]string{"foo", "test", "arg1", "arg2"}, []string{"arg1", "arg2"}, ""},
+		{[]string{"foo", "test", "--opt", "opt-value"}, []string{}, "opt-value"},
+		{[]string{"foo", "test", "--opt", "opt-value", "arg1"}, []string{"arg1"}, "opt-value"},
+		{[]string{"foo", "test", "--opt", "opt-value", "arg1", "arg2"}, []string{"arg1", "arg2"}, "opt-value"},
+		{[]string{"foo", "test", "arg1", "--opt", "opt-value"}, []string{"arg1"}, "opt-value"},
+		{[]string{"foo", "test", "arg1", "--opt", "opt-value", "arg2"}, []string{"arg1", "arg2"}, "opt-value"},
+
+		{[]string{"foo", "test", "--opt", "-opt-value"}, []string{}, "-opt-value"},
+		{[]string{"foo", "test", "--opt", "-opt-value", "arg1"}, []string{"arg1"}, "-opt-value"},
+		{[]string{"foo", "test", "--opt", "-opt-value", "arg1", "arg2"}, []string{"arg1", "arg2"}, "-opt-value"},
+		{[]string{"foo", "test", "arg1", "--opt", "-opt-value"}, []string{"arg1"}, "-opt-value"},
+		{[]string{"foo", "test", "arg1", "--opt", "-opt-value", "arg2"}, []string{"arg1", "arg2"}, "-opt-value"},
+
+		{[]string{"foo", "test", "--opt", "--opt-value"}, []string{}, "--opt-value"},
+		{[]string{"foo", "test", "--opt", "--opt-value", "arg1"}, []string{"arg1"}, "--opt-value"},
+		{[]string{"foo", "test", "--opt", "--opt-value", "arg1", "arg2"}, []string{"arg1", "arg2"}, "--opt-value"},
+		{[]string{"foo", "test", "arg1", "--opt", "--opt-value"}, []string{"arg1"}, "--opt-value"},
+		{[]string{"foo", "test", "arg1", "--opt", "--opt-value", "arg2"}, []string{"arg1", "arg2"}, "--opt-value"},
+	}
+
+	for _, tc := range cases {
+		tc := tc
+		t.Run(strings.Join(tc.testArgs, "_"), func(t *testing.T){
+			var (
+				args []string
+				opt string
+			)
+
+			cmd := Command{
+				Name:        "test",
+				Usage:       "this is for testing",
+				Description: "testing",
+				Action: func(c *Context) error {
+					args = c.Args()
+					opt = c.String("opt")
+					return nil
+				},
+				Flags: []Flag{StringFlag{
+					Name:  "opt",
+					Usage: "opt; set '-1' to disable",
+				}},
+			}
+
+			app := NewApp()
+			app.Writer = ioutil.Discard
+			app.ErrWriter = ioutil.Discard
+			app.Commands = []Command{cmd}
+
+			err := app.Run(tc.testArgs)
+
+			expect(t, err, nil)
+			expect(t, args, tc.expectedArgs)
+			expect(t, opt, tc.expectedOpt)
+		})
+
+	}
+}
+
 func TestCommand_Run_DoesNotOverwriteErrorFromBefore(t *testing.T) {
 	app := NewApp()
 	app.Commands = []Command{