As of July 21, 2020, Heroku supports deploying to the main branch: https://devcenter.heroku.com/changelog-items/1829

They also encourage customers to switch to main from master.

What command did you execute?

production deploy, on the main branch

What did you expect to happen?

Parity should run git push production main

What actually happened?

Parity couldn't find the nonexistent master branch and crashed.

$ git branch
* main
$ production deploy
error: src refspec master does not match any
error: failed to push some refs to 'https://git.heroku.com/hotline-webring-production.git'
zsh: exit 1     production deploy

Some information about your installation

• What's your operating system? macOS
• What's the output of which development, which staging, which production?
  Parity has had multiple installation channels, and it's not uncommon for an
  old version to be somewhere else in your path.
  • All are in /usr/local/bin/COMMAND
• If installed via Homebrew, what does brew list parity output?

  $ brew list parity
  /usr/local/Cellar/parity/3.3.0/bin/development
  /usr/local/Cellar/parity/3.3.0/bin/pr_app
  /usr/local/Cellar/parity/3.3.0/bin/production
  /usr/local/Cellar/parity/3.3.0/bin/staging
  /usr/local/Cellar/parity/3.3.0/lib/parity/ (5 files)
  /usr/local/Cellar/parity/3.3.0/lib/parity.rb
  

• If installed via Rubygems, what's the gem version?

N/A