triagebot: tweak welcome message

CONTRIBUTING.md

@@ -19,10 +19,14 @@ When you get a review, please take care of the requested changes in new commits.
 existing commits. Generally avoid force-pushing. The only time you should force push is when there
 is a conflict with the master branch (in that case you should rebase across master, not merge), and
 all the way at the end of the review process when the reviewer tells you that the PR is done and you
-should squash the commits. If you are unsure how to use `git rebase` to squash commits, use `./miri
-squash` which automates the process but leaves little room for customization. (All this is to work
-around the fact that Github is quite bad at dealing with force pushes and does not support `git
-range-diff`. Maybe one day Github will be good at git and then life can become easier.)
+should squash the commits. (All this is to work around the fact that Github is quite bad at
+dealing with force pushes and does not support `git range-diff`.)
+
+The recommended way to squash commits is to use `./miri squash`, which will make everything into a
+single commit. You will be asked for the commit message; please ensure it describes the entire PR.
+You can also use `git rebase` manually if you need more control (e.g. if there should be more than
+one commit at the end), but then please use `--keep-base` to ensure the PR remains based on the same
+upstream commit.
 
 Most PRs bounce back and forth between the reviewer and the author several times, so it is good to
 keep track of who is expected to take the next step. We are using the `S-waiting-for-review` and

triagebot.toml

@@ -16,17 +16,12 @@ allow-unauthenticated = [
 # Enables assigning users to issues and PRs.
 [assign]
 warn_non_default_branch = true
-contributing_url = "https://github.com/rust-lang/miri/blob/master/CONTRIBUTING.md"
+contributing_url = "https://github.com/rust-lang/miri/blob/master/CONTRIBUTING.md#pr-review-process"
 [assign.custom_welcome_messages]
-welcome-message = """
-Welcome, and thank you for contributing to Miri!
-To ensure a smooth reviewing experience, please read https://github.com/rust-lang/miri/blob/master/CONTRIBUTING.md#pr-review-process.
-In particular, please do not force-push to the PR branch except when you need to rebase due to a conflict or when the reviewer asks you for it.
-"""
+welcome-message = "(unused)"
 welcome-message-no-reviewer = """
-Welcome, and thank you for contributing to Miri!
-To ensure a smooth reviewing experience, please read https://github.com/rust-lang/miri/blob/master/CONTRIBUTING.md#pr-review-process.
-In particular, please do not force-push to the PR branch except when you need to rebase due to a conflict or when the reviewer asks you for it.
+Thank you for contributing to Miri!
+Please remember to not force-push to the PR branch except when you need to rebase due to a conflict or when the reviewer asks you for it.
 """
 
 [no-merges]
@@ -49,6 +44,12 @@ remove = []
 add = ["S-waiting-on-author"]
 unless = ["S-blocked", "S-waiting-on-team", "S-waiting-on-review"]
 
+[autolabel."S-waiting-on-review"]
+new_pr = true
+
+[autolabel."S-waiting-on-author"]
+new_draft = true
+
 # Automatically close and reopen PRs made by bots to run CI on them
 [bot-pull-requests]