Cohesion Git History explorer

cohesion_git_history.sh

#/bin/bash
# For an unknown reason, the Acquia Site Studio repositories package their
# releases in a way that prevents comparing code changes between releases.
# Maybe this is intentional as a kind of security through obscurity. Maybe it
# is unintentional and just a part of a flawed release practice. Either way,
# the source code is GPL'ed on Github which lends itself to being able to track
# the changes between versions. That is exactly what this script does.
##
## Usage:
##   ./cohesion_git_history.sh https://github.com/acquia/cohesion
##   ./cohesion_git_history.sh https://github.com/acquia/cohesion-theme
##
## After executing these commands you'll end up with two folders in the current
## directory, one for cohesion and one for cohesion-theme that contain a proper
## git history constructed between releases that can be used to understand and
## inspect code changes incurred for each release.
##
## You can then leverage git history exploration tooling such as Sublime Merge
## or `git` commands to see and compare differences between versions:
##
##   cd cohesion
##   git diff 7.3.1..7.3.2
##   cd ../cohesion-theme
##   git diff 7.3.1..7.3.2
#
# Uncomment to show commands output.
# set -x
set -e

# Silence output from pushd.
pushd () {
    command pushd "$@" > /dev/null
}

# Silence output from popd.
popd () {
    command popd "$@" > /dev/null
}

# Show usage text if no argument is specified.
if [ -z "$1" ]; then
    sed -n 's/^##//p' $(basename "$0")
    exit 1;
fi

repo=$1
project_name=$(echo $repo | cut -d"/" -f5)

rm -rf $project_name
mkdir -p $project_name
mkdir -p .cache/
pushd $project_name
git init . --quiet
popd

refs=$(git ls-remote --refs --tags $repo '*.*.*' | sed -E 's/^[[:xdigit:]]+[[:space:]]+refs\/tags\/(.+)/\1/g')

for ref in $refs; do
    if [[ ! -f ".cache/$project_name-$ref.tar.gz" ]]; then
        echo "downloading $repo/archive/$ref.tar.gz"
        curl --silent -L $repo/archive/$ref.tar.gz --output ".cache/$project_name-$ref.tar.gz"
    else
        echo "skipping $repo/archive/$ref.tar.gz - .cache/$project_name-$ref.tar.gz file exists"
    fi
    pushd $project_name
    find . -not -path "./.git/*" -not -name ".git" -delete
    popd
    tar zxf .cache/$project_name-$ref.tar.gz --strip-components 1 -C $project_name
    pushd $project_name
    git add .
    git commit -m "$ref"
    popd
done