git-town has unnecessary warnings about conflicting commands

Summary

It seems the git-town package is configured to warn about providing the git-sync binary, but this is not true. git-town only supplies the git-town binary. This warning is not needed:

Error: Cannot install git-extras because conflicting formulae are installed.

git-town: because git-extras also ships a git-sync binary

Details

[X] Confirmed this is a problem with brew installing one, specific formula and not every time you run brew? If it's a general brew problem please file this issue at https://github.com/Homebrew/brew/issues/new. If it's a brew cask problem please file this issue at https://github.com/Homebrew/caskroom/homebrew-cask/new
[X] Ran brew update and retried your prior step?
[X] Ran brew doctor, fixed all issues and retried your prior step?
[X] Ran brew gist-logs <formula> (where <formula> is the name of the formula that failed) and included the output link?
[X] If brew gist-logs didn't work: ran brew config and brew doctor and included their output with your issue?

$ brew config
HOMEBREW_VERSION: 1.2.1-40-gdd5d4880d
ORIGIN: https://github.com/Homebrew/brew
HEAD: dd5d4880dc8518a987a5f0f0cbc43399180b7396
Last commit: 8 hours ago
Core tap ORIGIN: https://github.com/Homebrew/homebrew-core
Core tap HEAD: b746d2cc4fdcd29c5abdf2373c658d83de851713
Core tap last commit: 2 hours ago
HOMEBREW_PREFIX: /usr/local
HOMEBREW_REPOSITORY: /usr/local/Homebrew
HOMEBREW_CELLAR: /usr/local/Cellar
HOMEBREW_BOTTLE_DOMAIN: https://homebrew.bintray.com
CPU: quad-core 64-bit broadwell
Homebrew Ruby: 2.0.0-p648
Clang: 8.1 build 802
Git: 2.13.0 => /usr/local/bin/git
Perl: /usr/bin/perl
Python: /usr/local/bin/python => /usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/bin/python2.7
Ruby: /usr/local/bin/ruby => /usr/local/Cellar/ruby/2.4.1_1/bin/ruby
Java: 1.8.0_121
macOS: 10.12.4-x86_64
Xcode: 8.3.2
CLT: 8.3.2.0.1.1492020469
X11: N/A
$ brew doctor
Your system is ready to brew.

To help us debug your issue please explain:

What you were trying to do (and why)?

Install git-town, then upgrade git-extras
What happened (include command output)?

$ brew install git-town
Updating Homebrew...
==> Auto-updated Homebrew!
Updated Homebrew from 7000f50d5 to dd5d4880d.
Updated 5 taps (burntsushi/ripgrep, caskroom/cask, caskroom/versions, homebrew/core, homebrew/science).
==> New Formulae
twine-pypi
==> Updated Formulae
ammonite-repl              git-flow-avh               par2
antigen                    git-town                   parallel ✔
apache-archiva             gmime                      pmd
bandcamp-dl                grc                        redpen
caddy                      gtksourceview3             roswell
creduce                    homebrew/science/vigra     saltstack
diffutils                  jenkins                    varnish
firebase-cli               mkvtoolnix                 varnish@4
flint-checker              nano                       vim
fwup                       nativefier

==> Downloading https://homebrew.bintray.com/bottles/git-town-4.0.1.sierra.bottl
######################################################################## 100.0%
==> Pouring git-town-4.0.1.sierra.bottle.tar.gz
==> Using the sandbox
🍺  /usr/local/Cellar/git-town/4.0.1: 5 files, 5MB

$ brew upgrade
==> Upgrading 18 outdated packages, with result:
git-extras 4.3.0, git-lfs 2.1.1, glib 2.52.2, gobject-introspection 1.52.1, grafana 4.2.0, imagemagick 7.0.5-7, influxdb 1.2.4, mercurial 4.2, node 7.10.0, parallel 20170522, purescript 0.11.4, burntsushi/ripgrep/ripgrep-bin 0.5.2, syncthing 0.14.28, telegraf 1.3.0, terraform 0.9.5, the_silver_searcher 1.0.3, yarn 0.24.5, youtube-dl 2017.05.18.1
==> Upgrading git-extras
Error: Cannot install git-extras because conflicting formulae are installed.

  git-town: because git-extras also ships a git-sync binary

Please `brew unlink git-town` before continuing.

Unlinking removes a formula's symlinks from /usr/local. You can
link the formula again after the install finishes. You can --force this
install, but the build may fail or cause obscure side-effects in the
resulting software.

What you expected to happen

Upgrade should be performed.
Step-by-step reproduction instructions (by running brew install commands)
- Install git-extras
- Install git-town
- Upgrade git-extras

Homebrew / homebrew-core

git-town has unnecessary warnings about conflicting commands #13805

Summary

Details