Import foreign commit prefixed instead of transplanting the tree

[kentfredric]

verbatim

This will help avoid problems with rebase.

NOTE: the .gitrepo file is still added at the merge stage, and that
file will be lost in subsequent rebases/merges.

Also, the equivalent code for pull is not in place yet.

It relies on knowledge of the internal format specification for the raw
tree blob object ( what you get if you do git cat-file tree <TREESHA> )
and writes one by hand with a bit of ninja tricks from perl's pack
function.

This is because silly git, unlike everywhere else in git, stores SHA1s
in TREE blobs in binary encoding instead of in Hex. :(

Tree Blob format is

  TYPE SPACE FILENAME NULL BINARYSHA1

Where TYPE is 040000 for directories/trees.

Signed-off-by: Kent Fredric kentfredric@gmail.com

[kentfredric]

I'm not entirely sure you'd want to stuff the .gitrepo file in the parent2 commit either, its doable, but a little bit of legwork, and it would require more code to remove.

Oh, and "Former" would be impossible if it was in that commit, because it would have to refer to itself.

[kentfredric]

In branch https://github.com/ingydotnet/git-subrepo/tree/transplant_prefix

[ingydotnet]

I rewrote the clone command to fetch the remote, checkout the content into the subdir as a WORK TREE, add the .gitrepo file and then do it all as one commit. I changed former to parent, as it now points to the mainline HEAD commit before the clone.

I also made the commit message look better (I hope) so the history is hopefully very nice.