Make subdirs of git repository their own git repos

Question

As it turns out, this question asked the same thing http://stackoverflow.com/questions/359424/detach-subdirectory-into-separate-git-repository

I decided to learn git and to keep my programming homework in a git repo. I think it was a good idea. Now I'm wondering about something:

I had a single git repo with a subdirectory for each assignment. I'm wondering if there's a sane way to make each of the subdirectories into its own git repo, retaining the history associated with those files. It seems like "git filter-branch --subirectory-filter" is part of the answer, but I'm not sure what to do.

EDIT

To clarify: My structure is like this

superdir  
  .git  
  subdir1
  subdir2
  subdir3

I'd like my structure to be more like this

superdir    
  subdir1
    .git
  subdir2
    .git
  subdir3
    .git

Can I do it?

Answer 1

You're probably looking for git submodules, but I'd just change your layout to have the top level not be a git repo and just have the subdir repos managed independently.

Answer 2

Why not place each class as it's own repo and each assignment as it's own branch? As I look back on my college coursework, that is how I would organize things.

Answer 3

Use a script such as the one below:

#! /bin/bash

superdir=file:///tmp/superdir
subdirs=(subdir1 subdir2 subdir3)

for dir in ${subdirs[@]}; do
  echo "Rewriting $dir..."
  git clone --quiet $superdir "$dir" || exit 1
  cd "$dir"

  # workaround for git-1.6.4.2 on Cygwin 1.7
  # otherwise, git-filter-branch complains about a dirty branch
  git reset --hard -q

  git filter-branch --subdirectory-filter "$dir" HEAD >/dev/null
  git reflog expire --expire=0 --all
  git gc --quiet --prune=0
  cd ..
done

Starting with a superdir repo whose structure is

$ ls -a . *
.:
.  ..  .git  subdir1  subdir2  subdir3

subdir1:
.  ..  file1

subdir2:
.  ..  file2

subdir3:
.  ..  file3

the result is

$ ls -a . *
.:
.  ..  subdir1 subdir2  subdir3

subdir1:
.  ..  .git  file1

subdir2:
.  ..  .git  file2

subdir3:
.  ..  .git  file3