extraction - How to extract one file with commit history from a git repo with index-filter & co

Question

My situation was, I have a git repo converted from SVN to HG to GIT, and I wanted to extract just one source file. I also had weird characters like aì (an encoding mismatch corrupted Unicode ?) and spaces in the filenames.

Seems it's not particularly easy, and that's the reason I'll be answering my own question despite many similar questions regarding git [index-filter|subdirectory-filter|filter-tree], as I needed to use all the previous to achieve this!

So the question is: "How can I extract one file from a repository and place it at the root of the new repo?"

Answer 1

A faster and easier-to-understand filter that accomplishes the same thing:

git filter-branch --index-filter '
                        git read-tree --empty
                        git reset $GIT_COMMIT -- $your $files $here
                ' 
        -- --all -- $your $files $here