guilt: export current state of patch queue

This feature allow us easily create guilt queue snapshot.
I use this snapshots for document purposes.
Each time i'm compile a kernel i'm create the snapshot
and attach it to binarry tarball. This is similar to
well known kernel identification (mainstream_commit + patchset)
Let's use git style patch format here because it contains
parent commit id, and parent commit of the first patch refers
to original_commit_id, So patch-set queue becomes self document.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
guilt: add import support for mbox files

This tiny feature dramatically simplify patch-set management.Patches
from mailbox imported to guilt control with corresponding fancy names.
Every day use case may looks like follows:
1: #read mail, select and save some interested patches to mbox.
2: guilt import -m patch-set.mbox  # feed mbox to guilt.
3: quilt push -a                   # push the patch set.
4: $EDITOR    			   # dive in to new stuff

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
guilt: Start editor at the line of current a top patch

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>