This was put in place for Go < 1.11, which we no longer support in CI.

This reverts commit 75c54101.

remove bmizerany/assert

Add more Fish completions to pull-request

Add openSUSE and zypper to install instructions

Since the CI job runs without the full git history, and since we
commonly get release notes from the annotated git tag, eliminate the
obsolete code path that tried to generate the changelog.

https://github.com/github/hub/runs/488291084

Update snap install command.

Go 1.13: `Post <URL>: <message>`
Go 1.14: `Post "<URL>": <message>`

Since we have an existing test that includes this error message, make
sure that `url.Error`s are output without quotes around the URL.

Use `git symbolic-ref` to read the branch name for HEAD

This affects reading the current branch as well as reading the default
branch for a remote. Because we're no longer trying to read the ref
manually from the filesystem, this approach works with git worktrees.

Fixes #2467