Gerrit workflow - push single commit to topic branch -

i want push single commit gerrit without affecting other commits in same topic branch. unfortunately don't have test instance of gerrit experiment with.

scenario: have contributed topic branch project, in review, , other developers have updated parts of it. wish make changes on top of updates.

to pull changes other developer in commit wish edit, interactive rebase locally make own changes, push gerrit, making sure change-id still same. adds new version of file patchset review.

problem: when tried push single commit gerrit, other commits in topic-branch pushed, overwriting changes other developers.

here syntax used:

git push gerrit 3089c9f56542461dce738a9aa17bb743ed36e038:refs/publish/master/my-topic-branch 

i presume other commits in topic-branch pushed because of dependencies created gerrit.

would approach work instead, leaving out topic branch title?:

git push gerrit 3089c9f56542461dce738a9aa17bb743ed36e038:refs/publish/master 

i tried approach previously, pushing specific changeset:

git push gerrit a95cc0dcd7a8fd3e70b1243aa466a96de08ae731:refs/changes/12345 

however, in trying again getting unpack error:

error: unpack failed: error missing tree 9172313b907b160d15e260d5f7d51689f467b858 

related question: when pull other developers' changes gerrit, how can make sure have pulled files contributed in topic-branch? if select topmost change in gerrit in topic-branch, , use pull command stated in web ui, seems of files in topic-branch updated locally, not all. need go through every single commit in topic-branch , issue relevant pull command?

i don't know commands of hand this:

1. make new branch of topic branch
2. merge commit want add topic branch new branch
3. push newly created merge gerrit