make sure to tag the current local sha we are building from

build-system/tasks/changelog.js

@@ -73,12 +73,14 @@ function getGitMetadata() {
         if (isDryrun) {
           return;
         }
-        return submitReleaseNotes(argv.version, gitMetadata.changelog);
+        return getCurrentSha().then(
+          submitReleaseNotes.bind(null, version, gitMetadata.changelog)
+        );
       })
       .catch(errHandler);
 }
 
-function submitReleaseNotes(version, changelog) {
+function submitReleaseNotes(version, changelog, sha) {
   var name = String(version);
   var options = {
     url: 'https://api.github.com/repos/ampproject/amphtml/releases',
@@ -90,7 +92,7 @@ function submitReleaseNotes(version, changelog) {
     json: true,
     body: {
       'tag_name': name,
-      'target_commitish': branch,
+      'target_commitish': sha,
       'name': name,
       'body': changelog,
       'draft': true,
@@ -109,6 +111,10 @@ function submitReleaseNotes(version, changelog) {
   });
 }
 
+function getCurrentSha() {
+  return gitExec({ args: 'rev-parse HEAD' });
+}
+
 function buildChangelog(gitMetadata, githubMetadata) {
   var titles = githubMetadata
       .filter(function(data) {