Git Presentation Demo: tree hashes

git-demo-tree-hashes.sh

# More info at http://unix.stackexchange.com/questions/165369/whats-the-difference-between-commit-hash-parent-hash-and-tree-hash-in-gi
# Make two git repositories with the same first commit and compare logs
for dir in {a,b}; do
    mkdir $dir
    (
        cd $dir
        (
            git init
            echo 'foo' > foo
            git add foo
            git commit --message 'Add foo'
        ) &>/dev/null
        git log --pretty=oneline
    )
done
# Make one commit to a, and the same to b but with an empty commit before it
(
    cd a
    (
        git commit --allow-empty --message 'Empty'
        git commit --allow-empty --message 'Empty'
        echo 'bar' >> foo
        git diff
        git commit --all --message 'Add bar to foo'
    ) &>/dev/null
    git log --pretty=oneline
)
(
    cd b
    (
        git commit --allow-empty --message 'Empty'
        git commit --allow-empty --message 'Empty again'
        echo 'bar' >> foo
        git diff
        git commit --all --message 'Add bar to foo'
    ) &>/dev/null
    git log --pretty=oneline
)