Also, I want this (and others like DNR, etc) is documented in the contribution guideline.

Used R= in the commit message based on other CLs i had seen. e.g.
https://go-review.googlesource.com/c/go/+/86035

My intention is to remove them from my commit messages once the tree is open and before commit but I too see the problem that it is easy to forget.

I suppose we could also make the bot mark them as Do-Not-Submit (or just -2 them) until the R=go1.N tree is open too.

But do we care about commit message prettiness?

I do.

For those who are heavy git mail users, we could add a secret flag (like -trybot) to auto-add an R=go1.N comment.

A similar question exists for RELNOTE=yes. I would prefer to see them in gerrit but not commit messages, personally.

Does gerrit support pre-submit hooks? We could have gerrit rewrite away such lines in the commit message. Then out bot would just need to replicate the commit message annotations in gerrit comments.

Used R= in the commit message based on other CLs i had seen. [...]

My intention is to remove them from my commit messages once the tree is open and before commit but I too see the problem that it is easy to forget.

Same for me. Also, my idea was to save reviewer's time (even though https://golang.org/cl/91055 was then approved for go1.10) and for myself to keep track of my branches/CLs locally. Also being a git mail user, it would be nice to have a way to mark a CL targeting a specific R=go1.N locally as well as in gerrit (and have the two in sync).

I actually propose we stop using magic comments and start using CL-level tags in Gerrit. Gerrit calls the feature "hashtags", and it's now supported by the PolyGerrit UI. We're using them in Perkeep and they're great. It means we can search on them, too.

On their silly name: https://groups.google.com/forum/#!topic/repo-discuss/jZ0raMyuiG0

https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#get-hashtags
https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#set-hashtags

Example Gerrit search: https://camlistore-review.googlesource.com/q/is:open+-owner:mathieu+-hashtag:op (we use the "op" tag in Perkeep to mean that it's the CL author's turn to do something).

/cc @andybons

(we use the "op" tag in Perkeep to mean that it's the CL author's turn to do something).

This can also be achieved by setting the “assignee” field, right?

This can also be achieved by setting the “assignee” field, right?

Maybe. It was just an example.