[RFC PATCH 0/3] Partial clone: promised blobs (formerly "missing blobs")

These patches are part of a set of patches implementing partial clone, as you can see here:

https://github.com/jonathantanmy/git/tree/partialclone

In that branch, clone with batch checkout works, as you can see in the README. The code and tests are generally done, but some patches are still missing documentation and commit messages.

These 3 patches implement the foundational concept - formerly known as "missing blobs" in the "missing blob manifest", I decided to call them "promised blobs". The repo knows their object names and sizes. It also does not have the blobs themselves, but can be configured to know how to fetch them.

An older version of these patches was sent as a single demonstration patch in versions 1 to 3 of [1]. In there, Junio suggested that I have only one file containing missing blob information. I have made that suggested change in this version.

One thing remaining is to add a repository extension [2] so that older versions of Git fail immediately instead of trying to read missing blobs, but I thought I'd send these first in order to get some initial feedback.

[1] https://public-inbox.org/git/cover.1497035376.git.jonathantanmy@google.com/ [2] Documentation/technical/repository-version.txt

Jonathan Tan (3):
  promised-blob, fsck: introduce promised blobs
  sha1-array: support appending unsigned char hash
  sha1_file: add promised blob hook support

 Documentation/config.txt               |   8 ++
 Documentation/gitrepository-layout.txt |   8 ++
 Makefile                               |   1 +
 builtin/cat-file.c                     |   9 ++
 builtin/fsck.c                         |  13 +++
 promised-blob.c                        | 170 +++++++++++++++++++++++++++++++++
 promised-blob.h                        |  27 ++++++
 sha1-array.c                           |   7 ++
 sha1-array.h                           |   1 +
 sha1_file.c                            |  44 ++++++---
 t/t3907-promised-blob.sh               |  65 +++++++++++++
 t/test-lib-functions.sh                |   6 ++
 12 files changed, 345 insertions(+), 14 deletions(-)
 create mode 100644 promised-blob.c
 create mode 100644 promised-blob.h
 create mode 100755 t/t3907-promised-blob.sh