[PATCH 0/4] upload-pack: support a missing-action

`git pack-objects` already supports a `--missing=<missing-action>` option, so that it can avoid erroring out if some objects aren't available.

It is interesting to have `git upload-pack` support a similar way to avoid sending some objects in case they aren't available on the server.

For example, in case both the server and the client are using a separate promisor remote that contain some objects, it can be better if the server doesn't try to send such objects back to the client, but instead let the client get those objects separately from the promisor remote. (The client needs to have the separate promisor remote configured, for that to work.)

Another example could be a server where some objects have been corrupted or deleted. It could still be useful for clients who could get those objects from another source, like perhaps a different client, to be able to fetch or clone from the server.

As `git rev-list` also supports a `--missing=<missing-action>` option, the first 3 patches in this series are about refactoring related code from both `git rev-list` and `git pack-objects` into new "missing.{c,h}" files. Patch 4/4 then adds a new `uploadpack.missingAction` configuration variable.

Christian Couder (4):
  rev-list: refactor --missing=<missing-action>
  missing: support rejecting --missing=print
  pack-objects: use the missing action API
  upload-pack: allow configuring a missing-action

 Documentation/config/uploadpack.txt |   9 ++
 Makefile                            |   1 +
 builtin/pack-objects.c              |  46 +++++-----
 builtin/rev-list.c                  |  41 ++-------
 missing.c                           |  42 ++++++++++
 missing.h                           |  20 +++++
 t/t5706-upload-pack-missing.sh      | 125 ++++++++++++++++++++++++++++
 upload-pack.c                       |  19 +++++
 8 files changed, 244 insertions(+), 59 deletions(-)
 create mode 100644 missing.c
 create mode 100644 missing.h
 create mode 100755 t/t5706-upload-pack-missing.sh