not set --env if thvariable is not present

close containers#3648

podman create and podman run do not set --env value if the environment is not present with a value

Signed-off-by: Qi Wang <qiwan@redhat.com>

cmd/podman/shared/parse/parse.go

@@ -126,8 +126,9 @@ func parseEnv(env map[string]string, line string) error {
 			}
 		} else {
 			// if only a pass-through variable is given, clean it up.
-			val, _ := os.LookupEnv(name)
-			env[name] = val
+			if val, ok := os.LookupEnv(name); ok {
+				env[name] = val
+			}
 		}
 	}
 	return nil

docs/podman-create.1.md

@@ -253,7 +253,7 @@ You need to specify multi option commands in the form of a json string.
 
 Set environment variables
 
-This option allows you to specify arbitrary environment variables that are available for the process that will be launched inside of the container. If you specify a environment variable without a value, podman will check the host environment for a value or set the environment to "". If you specify a environment variable ending in --*--, podman will search the host environment for variables starting with the prefix and add them to the container.  If you want to add an environment variable with a ***** following it, then you need to set a value.
+This option allows you to specify arbitrary environment variables that are available for the process that will be launched inside of the container. If you specify a environment variable without a value, podman will check the host environment for a value or not set the environment. If you specify a environment variable ending in --*--, podman will search the host environment for variables starting with the prefix and add them to the container.  If you want to add an environment variable with a ***** following it, then you need to set a value.
 
 See **Environment** note below for precedence.
 

docs/podman-run.1.md

@@ -260,7 +260,7 @@ You need to specify multi option commands in the form of a json string.
 
 Set environment variables
 
-This option allows you to specify arbitrary environment variables that are available for the process that will be launched inside of the container. If you specify a environment variable without a value, podman will check the host environment for a value or set the environment to "". If you specify a environment variable ending in --*--, podman will search the host environment for variables starting with the prefix and add them to the container.  If you want to add an environment variable with a ***** following it, then you need to set a value.
+This option allows you to specify arbitrary environment variables that are available for the process that will be launched inside of the container. If you specify a environment variable without a value, podman will check the host environment for a value or not set the environment. If you specify a environment variable ending in --*--, podman will search the host environment for variables starting with the prefix and add them to the container.  If you want to add an environment variable with a ***** following it, then you need to set a value.
 
 See **Environment** note below for precedence.
 

test/e2e/run_test.go

@@ -213,6 +213,12 @@ var _ = Describe("Podman run", func() {
 		Expect(match).Should(BeTrue())
 		os.Unsetenv("FOO")
 
+		session = podmanTest.Podman([]string{"run", "--rm", "--env", "FOO", ALPINE, "printenv", "FOO+test"})
+		session.WaitWithDefaultTimeout()
+		fmt.Println(session.OutputToString())
+		Expect(len(session.OutputToString())).To(Equal(0))
+		Expect(session.ExitCode()).To(Equal(0))
+
 		session = podmanTest.Podman([]string{"run", "--rm", ALPINE, "printenv"})
 		session.WaitWithDefaultTimeout()
 		Expect(session.ExitCode()).To(Equal(0))