Fixing passing --database-url as global cli arg

--database-url is passed as global cli argument, this means it may be
not part of the current ArgMatches. To solve this we need to look recursivly
in all current subcommands for the database-url

diesel_cli/src/cli.rs

@@ -133,6 +133,7 @@ pub fn build_cli() -> App<'static, 'static> {
         .subcommand(generate_bash_completion_subcommand)
         .subcommand(infer_schema_subcommand)
         .setting(AppSettings::SubcommandRequiredElseHelp)
+        .setting(AppSettings::PropagateGlobalValuesDown)
 }
 
 fn migration_dir_arg<'a, 'b>() -> Arg<'a, 'b> {

diesel_cli/src/database.rs

@@ -312,10 +312,15 @@ pub fn schema_table_exists(database_url: &str) -> DatabaseResult<bool> {
     }.map_err(Into::into)
 }
 
-pub fn database_url(matches: &ArgMatches) -> String {
+fn database_url_from_cli(matches: &ArgMatches) -> Option<String> {
     matches
         .value_of("DATABASE_URL")
-        .map(|s| s.into())
+        .map(Into::into)
+        .or_else(|| matches.subcommand().1.and_then(|s| database_url_from_cli(s)))
+}
+
+pub fn database_url(matches: &ArgMatches) -> String {
+    database_url_from_cli(matches)
         .or_else(|| env::var("DATABASE_URL").ok())
         .unwrap_or_else(|| handle_error(DatabaseError::DatabaseUrlMissing))
 }