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+# Homebrew
+
+## TL;DR
+
+```shell
+# install/uninstall on os x
+/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
+/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall)"
+
+# prevent a formula from upgrading
+brew pin gnupg2
+
+# bring an installation up to speed from a Brewfile
+brew bundle
+brew bundle --global
+brew bundle --file $HOME/Brewfile --no-lock
+
+# dump all installed casks/formulae/images/taps into a Brewfile in the current directory
+brew bundle dump
+```
+
+## Configuration
+
+```shell
+# require SHA check for casks
+# change cask installation dir to the Application folder in the user HOME
+export HOMEBREW_CASK_OPTS="--require-sha --appdir $HOME/Applications"
+
+# print install times for each formula at the end of the run
+export HOMEBREW_DISPLAY_INSTALL_TIMES=1
+
+# do not automatically update before running some commands
+export HOMEBREW_NO_AUTO_UPDATE=1
+
+# do not print HOMEBREW_INSTALL_BADGE on a successful build
+export HOMEBREW_NO_EMOJI=1
+
+# do not use the GitHub API
+# avoid searches or fetching relevant issues after a failed install
+export HOMEBREW_NO_GITHUB_API=1
+
+# forbid redirects from secure HTTPS to insecure HTTP
+export HOMEBREW_NO_INSECURE_REDIRECT=1
+
+# only list updates to installed software
+export HOMEBREW_UPDATE_REPORT_ONLY_INSTALLED=1
+
+# pass the -A option when calling sudo
+export SUDO_ASKPASS=1
+```
+
+## Downgrade an application to a non-managed version
+
+### The easy way
+
+```sh
+brew unlink kubernetes-helm
+#install version 2.13.0
+brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/ed9dcb2cb455a816f744c3ad4ab5c18a0d335763/Formula/kubernetes-helm.rb
+brew switch kubernetes-helm 2.13.0
+```
+
+### The hard way
+
+[source](https://stackoverflow.com/questions/3987683/homebrew-install-specific-version-of-formula)
+[alternative source](https://www.fernandomc.com/posts/brew-install-legacy-hugo-site-generator/)
+
+```sh
+formula_name='kubernetes-helm'
+formula_version='2.13.1'
+
+cd $(brew --repository)/Library/Tapshomebrew/homebrew-core
+git log master -S${formula_version} -- Formula/${formula_name}.rb
+commit_id='<something>'  # insert commit id
+
+git checkout -b ${formula_name}-${formula_version} ${commit_id}
+HOMEBREW_NO_AUTO_UPDATE=1 brew install ${formula_name}
+# pin application if needed
+
+git checkout master
+git branch -d ${formula_name}-${formula_version}
+```
+
+## Gotchas
+
+- `moreutils` installs its own old version of `parallel`, which conflicts with the `parallel` formulae; install the standalone `gettext`, `parallel` and `sponge` to have their recent version
+
+## Further readings
+
+- [How to stop homebrew from upgrading itself on every run]
+- [macOS migrations with Brewfile]
+- [manpage]
+- Homebrew [bundle]
+
+[bundle]: https://github.com/Homebrew/homebrew-bundle
+[how to stop homebrew from upgrading itself on every run]: https://superuser.com/questions/1209053/how-do-i-tell-homebrew-to-stop-running-brew-update-every-time-i-want-to-install/1209068#1209068
+[macos migrations with brewfile]: https://openfolder.sh/macos-migrations-with-brewfile
+[manpage]: https://docs.brew.sh/Manpage