HomeBrew Dart version installer

install-dart-version.sh

#!/usr/bin/env bash

# install-dart-version.sh
#
# A script that installs a specific version of Dart using HomeBrew.
#
# Given a version, it'll first try to switch to a local install.
#
# If that version is not available, it will search through the Dart
# formula's history to find the right version.


# pipefail is important for `indent` to not swallow the exit code
set -o pipefail
indent() { sed 's/^/  /'; }

dart_version=$1

if [ -z "$dart_version" ]; then
    echo Installs the given Dart version using HomeBrew.
    echo
    echo "Usage: $0 <Dart version>"
    exit 0
fi

echo "Installing Dart \"$dart_version\"..."
echo
echo Trying to use previously installed version...

brew switch dart "$dart_version" 2>&1 | indent
brew_switch_exit_code=$?

if [ $brew_switch_exit_code -eq 0 ]; then
    echo
    echo "Dart \"$dart_version\" installed!"
    exit 0
fi

echo
echo "Dart \"$dart_version\" not already installed. Searching formula history..."
echo

cd $(dirname "$(brew formula dart)") || exit 1
# Finding revision based on this message search is brittle, but so far, all commit messages are formatted consistently.
REVISION=$(git log --pretty=format:%H --grep "Updated stable branch to revision $dart_version\$")

if [ -z "$REVISION" ]; then
    echo 'No matching Dart version found. Try running `brew update` and rerunning this script.'
    exit 1
fi

echo "Found formula revision with the matching Dart version!"
git log -1 "$REVISION" 2>&1 | indent

echo
echo Installing...
echo

# Update the working copy to the given revision
git checkout "$REVISION" -- . || exit 1

# Install the formula in the working copy
brew unlink dart
brew install dart

# Undo the working copy changes
git reset --hard