fixup! fix(git-node): fix handling of existing trailers

Author: aduh95

lib/session.js

@@ -127,6 +127,7 @@ export default class Session {
     writeJson(this.sessionPath, {
       state: STARTED,
       prid: this.prid,
+      backport: this.backport,
       // Filter out getters, those are likely encrypted data we don't need on the session.
       config: Object.entries(Object.getOwnPropertyDescriptors(this.config))
         .reduce((pv, [key, desc]) => {
@@ -271,6 +272,7 @@ export default class Session {
     const sess = this.session;
     if (sess.prid) {
       this.prid = sess.prid;
+      this.backport = sess.backport;
       this.config = sess.config;
     }
     return this;