Rework label parsing

We attempted to share all logic for parsing labels and
environment variables, which on the surface makes lots of sense
(both are formatted key=value so parsing logic should be
identical) but has begun to fall apart now that we have added
additional logic to environment variable handling. Environment
variables that are unset, for example, are looked up against
environment variables set for the process. We don't want this for
labels, so we have to split parsing logic.

Fixes #3854

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

test/e2e/create_test.go

@@ -304,4 +304,42 @@ var _ = Describe("Podman create", func() {
 		session.WaitWithDefaultTimeout()
 		Expect(session).To(Not(Equal(0)))
 	})
+
+	It("podman create with unset label", func() {
+		// Alpine is assumed to have no labels here, which seems safe
+		ctrName := "testctr"
+		session := podmanTest.Podman([]string{"create", "--label", "TESTKEY1=", "--label", "TESTKEY2", "--name", ctrName, ALPINE, "top"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+
+		inspect := podmanTest.Podman([]string{"inspect", ctrName})
+		inspect.WaitWithDefaultTimeout()
+		data := inspect.InspectContainerToJSON()
+		Expect(len(data)).To(Equal(1))
+		Expect(len(data[0].Config.Labels)).To(Equal(2))
+		_, ok1 := data[0].Config.Labels["TESTKEY1"]
+		Expect(ok1).To(BeTrue())
+		_, ok2 := data[0].Config.Labels["TESTKEY2"]
+		Expect(ok2).To(BeTrue())
+	})
+
+	It("podman create with set label", func() {
+		// Alpine is assumed to have no labels here, which seems safe
+		ctrName := "testctr"
+		session := podmanTest.Podman([]string{"create", "--label", "TESTKEY1=value1", "--label", "TESTKEY2=bar", "--name", ctrName, ALPINE, "top"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+
+		inspect := podmanTest.Podman([]string{"inspect", ctrName})
+		inspect.WaitWithDefaultTimeout()
+		data := inspect.InspectContainerToJSON()
+		Expect(len(data)).To(Equal(1))
+		Expect(len(data[0].Config.Labels)).To(Equal(2))
+		val1, ok1 := data[0].Config.Labels["TESTKEY1"]
+		Expect(ok1).To(BeTrue())
+		Expect(val1).To(Equal("value1"))
+		val2, ok2 := data[0].Config.Labels["TESTKEY2"]
+		Expect(ok2).To(BeTrue())
+		Expect(val2).To(Equal("bar"))
+	})
 })