Fix context.IsSet()

Accidentally mangled the implementation when merging master into the
`v2` branch resulting in a dropped test.

context.go

@@ -78,7 +78,7 @@ func (c *Context) IsSet(name string) bool {
 	for _, envVar := range envVarValues.Interface().([]string) {
 		envVar = strings.TrimSpace(envVar)
 		if envVal := os.Getenv(envVar); envVal != "" {
-			continue
+			return true
 		}
 	}
 

context_test.go

@@ -2,6 +2,7 @@ package cli
 
 import (
 	"flag"
+	"os"
 	"sort"
 	"testing"
 	"time"
@@ -157,6 +158,68 @@ func TestContext_IsSet(t *testing.T) {
 	expect(t, ctx.IsSet("bogus"), false)
 }
 
+// XXX Corresponds to hack in context.IsSet for flags with EnvVar field
+// Should be moved to `flag_test` in v2
+func TestContext_IsSet_fromEnv(t *testing.T) {
+	var (
+		timeoutIsSet, tIsSet, noEnvVarIsSet, nIsSet             bool
+		globalTimeoutIsSet, TIsSet, globalNoEnvVarIsSet, NIsSet bool
+	)
+
+	os.Clearenv()
+	os.Setenv("GLOBAL_APP_TIMEOUT_SECONDS", "15.5")
+	os.Setenv("APP_TIMEOUT_SECONDS", "15.5")
+	a := App{
+		Flags: []Flag{
+			&Float64Flag{
+				Name:    "global-timeout",
+				Aliases: []string{"T"},
+				EnvVars: []string{"GLOBAL_APP_TIMEOUT_SECONDS"},
+			},
+			&Float64Flag{
+				Name:    "global-no-env-var",
+				Aliases: []string{"N"},
+			},
+		},
+		Commands: []*Command{
+			{
+				Name: "hello",
+				Flags: []Flag{
+					&Float64Flag{
+						Name:    "timeout",
+						Aliases: []string{"t"},
+						EnvVars: []string{"APP_TIMEOUT_SECONDS"},
+					},
+					&Float64Flag{
+						Name:    "no-env-var",
+						Aliases: []string{"n"},
+					},
+				},
+				Action: func(ctx *Context) error {
+					globalTimeoutIsSet = ctx.IsSet("global-timeout")
+					TIsSet = ctx.IsSet("T")
+					globalNoEnvVarIsSet = ctx.IsSet("global-no-env-var")
+					NIsSet = ctx.IsSet("N")
+					timeoutIsSet = ctx.IsSet("timeout")
+					tIsSet = ctx.IsSet("t")
+					noEnvVarIsSet = ctx.IsSet("no-env-var")
+					nIsSet = ctx.IsSet("n")
+					return nil
+				},
+			},
+		},
+	}
+	a.Run([]string{"run", "hello"})
+	expect(t, globalTimeoutIsSet, true)
+	expect(t, TIsSet, true)
+	expect(t, globalNoEnvVarIsSet, false)
+	expect(t, NIsSet, false)
+	expect(t, timeoutIsSet, true)
+	expect(t, tIsSet, true)
+	expect(t, noEnvVarIsSet, false)
+	expect(t, nIsSet, false)
+}
+
 func TestContext_NumFlags(t *testing.T) {
 	set := flag.NewFlagSet("test", 0)
 	set.Bool("myflag", false, "doc")