dev-cmd/pr-pu{ll,blish}: handle PRs with an autosquash label

- request `autosquash` from the publish job in `pr-publish` if the PR is
  labelled with `autosquash`
- show a warning in `pr-pull` if called without `--autosquash` on a PR
  with the autosquash label.

Library/Homebrew/dev-cmd/pr-publish.rb

@@ -67,6 +67,10 @@ module Homebrew
 
       inputs[:pull_request] = issue
 
+      pr_labels = GitHub.pull_request_labels(user, repo, issue)
+      oh1 "Found `autosquash` label on ##{issue}. Requesting autosquash."
+      inputs[:autosquash] = true if pr_labels.include?("autosquash")
+
       if args.tap.present? && !T.must("#{user}/#{repo}".casecmp(tap.full_name)).zero?
         odie "Pull request URL is for #{user}/#{repo} but `--tap=#{tap.full_name}` was specified!"
       end

Library/Homebrew/dev-cmd/pr-pull.rb

@@ -308,11 +308,9 @@ module Homebrew
     Utils::Git.cherry_pick!(path, "--ff", "--allow-empty", *commits, verbose: args.verbose?, resolve: args.resolve?)
   end
 
-  def self.formulae_need_bottles?(tap, original_commit, user, repo, pull_request, args:)
+  def self.formulae_need_bottles?(tap, original_commit, labels, args:)
     return if args.dry_run?
 
-    labels = GitHub.pull_request_labels(user, repo, pull_request)
-
     return false if labels.include?("CI-syntax-only") || labels.include?("CI-no-bottles")
 
     changed_packages(tap, original_commit).any? do |f|
@@ -456,6 +454,11 @@ module Homebrew
         opoo "Current branch is #{tap.path.git_branch}: do you need to pull inside #{tap.path.git_origin_branch}?"
       end
 
+      pr_labels = GitHub.pull_request_labels(user, repo, pr)
+      if pr_labels.include?("autosquash") && !args.autosquash?
+        opoo "Pull request is labelled `autosquash`: do you need to pass `--autosquash`?"
+      end
+
       pr_check_conflicts("#{user}/#{repo}", pr)
 
       ohai "Fetching #{tap} pull request ##{pr}"
@@ -478,7 +481,7 @@ module Homebrew
             signoff!(tap.path, pull_request: pr, dry_run: args.dry_run?) unless args.clean?
           end
 
-          unless formulae_need_bottles?(tap, original_commit, user, repo, pr, args: args)
+          unless formulae_need_bottles?(tap, original_commit, pr_labels, args: args)
             ohai "Skipping artifacts for ##{pr} as the formulae don't need bottles"
             next
           end