brew update can be terribly slow for stale taps

[boblail]

brew config output

HOMEBREW_VERSION: 3.4.10-3-gbb3d970-dirty
ORIGIN: https://github.com/Homebrew/brew
HEAD: bb3d97030c68ed6d3074b4689a39a0ebb556fbf4
Last commit: 6 hours ago
Core tap ORIGIN: https://github.com/Homebrew/homebrew-core
Core tap HEAD: dbc32b7ea38309f8b0b91e9f1ecf68e17c8a519d
Core tap last commit: 8 minutes ago
Core tap branch: master
HOMEBREW_PREFIX: /usr/local
HOMEBREW_CASK_OPTS: []
HOMEBREW_CORE_GIT_REMOTE: https://github.com/Homebrew/homebrew-core
HOMEBREW_MAKE_JOBS: 16
HOMEBREW_NO_ANALYTICS: set
Homebrew Ruby: 2.6.8 => /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/ruby
CPU: 16-core 64-bit kabylake
Clang: 13.1.6 build 1316
Git: 2.35.1 => /usr/local/bin/git
Curl: 7.79.1 => /usr/bin/curl
macOS: 12.3.1-x86_64
CLT: 13.3.0.0.1.1645755326
Xcode: N/A

brew doctor output

Please note that these warnings are just used to help the Homebrew maintainers
with debugging if you file an issue. If everything you use Homebrew for is
working fine: please don't worry or file an issue; just ignore this. Thanks!

Warning: Some installed formulae are deprecated or disabled.
You should find replacements for the following formulae:
  bazaar

Warning: You have unlinked kegs in your Cellar.
Leaving kegs unlinked can lead to build-trouble and cause formulae that depend on
those kegs to fail to run properly once built. Run `brew link` on these:
  kubernetes-cli

Warning: You have uncommitted modifications to Homebrew/brew.
If this is a surprise to you, then you should stash these modifications.
Stashing returns Homebrew to a pristine state but can be undone
should you later need to do so for some reason.
  cd /usr/local/Homebrew && git stash && git clean -d -f

Uncommitted files:
   M Library/Homebrew/cmd/update-report.rb
   M Library/Homebrew/cmd/update.sh

Verification

• I ran brew update and am still able to reproduce my issue.
• I have resolved all warnings from brew doctor and that did not fix my problem.

What were you trying to do (and why)?

If you run brew update on a very stale tap, the update-report takes a long time.

For example,

git -C "$(brew --repo homebrew/core)" reset --hard e27948a0f03 # commit on master from Dec 2021
time brew update

takes 2m40s on my MacBook Pro (2.3 GHz 8-Core Intel Core i9)

If I comment out just the call to brew update-report, the same operation takes 3.8s — so the expense is entirely in brew update-report.

Alternately, if I comment out just lines 373-383 in update-report.rb, the same operation takes 10.3s.

brew update --preinstall also bypasses these lines; but it cuts corners in update.sh as well.

What happened (include all command output)?

(Described above)

What did you expect to happen?

I would expect brew update not to take minutes, even for stale taps

Step-by-step reproduction instructions (by running brew commands)

(Described above)

[MikeMcQuaid]

Will review and consider accepting a PR that either:

• maintains current functionality and speeds this up
• removes this behaviour entirely and has another maintainer than just me agree with it

[boblail]

I think this is resolved by #13299 and #13375