Make a new repo from a subdirectory of an original repo

filter_subdir.sh

# Please don't just RUN this. Do it step-by-step.

user=bocoup
orig_repo=training
new_repo=training-jquery
subdir=jquery-conference

# Pull down the original repo.
git clone git@github.com:$user/$orig_repo.git $new_repo
# Repo, I'm in you.
cd $new_repo

# Rewrite history, removing everything but files in the "subdir" directory.
# This moves all those files into the root as well. Not sure that this
# handles all refs, not sure that I care.
git filter-branch --subdirectory-filter $subdir -- --all
# Verify there aren't any missing renamed files, et (per man page).
git log --name-only --follow --all -- filename

# In the GitHub admin, create a new repo for "user" with name "new_repo".

# Remove the "orig_repo" origin remote.
git remote rm origin
# Add the new "new_repo" origin remote.
git remote add origin git@github.com:$user/$new_repo.git
# Push to GitHub.
git push -u origin master