If a filter is changed on a partial clone repository, for example from
blob:none to blob:limit=1m, there is currently no straightforward way to
bulk-refetch the objects that match the new filter for existing local
commits. This is because the client will report commits as "have" during
fetch negotiation and any dependent objects won't be included in the
transferred pack. Another use case is discussed at [1].

This patch series introduces a --repair option to fetch & fetch-pack to
enable doing a full fetch without performing any commit negotiation with the
remote, as for a fresh clone. It builds upon cbe566a071 ("negotiator/noop:
add noop fetch negotiator", 2020-08-18). While a key use case is described
above for partial clones, a user could also use --repair to fix a corrupted
object database by performing a refetch of objects that should already be
present, establishing a better workflow than deleting the local repository
and re-cloning.

 * Using --repair will produce duplicated objects between the existing and
   newly fetched packs, but maintenance will clean them up when it runs
   automatically post-fetch (if enabled).
 * If a user fetches with --repair applying a more restrictive partial clone
   filter than previously (eg: blob:limit=1m then blob:limit=1k) the
   eventual state is a no-op, since any referenced object already in the
   local repository is never removed. More advanced repacking which could
   improve this scenario is currently proposed at [2].

[1]
https://public-inbox.org/git/aa7b89ee-08aa-7943-6a00-28dcf344426e@syntevo.com/
[2]
https://public-inbox.org/git/21ED346B-A906-4905-B061-EDE53691C586@gmail.com/

Changes since RFC (v1):

 * Changed the name from "refilter" to "repair"
 * Removed dependency between server-side support for filtering and repair
 * Added a test case for a shallow clone
 * Post-fetch auto maintenance now strongly encourages
   repacking/consolidation

Robert Coup (8):
  fetch-negotiator: add specific noop initializor
  fetch-pack: add repairing
  builtin/fetch-pack: add --repair option
  fetch: add --repair option
  t5615-partial-clone: add test for fetch --repair
  maintenance: add ability to pass config options
  fetch: after repair, encourage auto gc repacking
  doc/partial-clone: mention --repair fetch option

 Documentation/fetch-options.txt           | 10 +++++
 Documentation/git-fetch-pack.txt          |  4 ++
 Documentation/technical/partial-clone.txt |  3 ++
 builtin/am.c                              |  2 +-
 builtin/commit.c                          |  2 +-
 builtin/fetch-pack.c                      |  4 ++
 builtin/fetch.c                           | 38 ++++++++++++++--
 builtin/merge.c                           |  2 +-
 builtin/rebase.c                          |  2 +-
 fetch-negotiator.c                        |  5 +++
 fetch-negotiator.h                        |  8 ++++
 fetch-pack.c                              | 50 +++++++++++++--------
 fetch-pack.h                              |  1 +
 remote-curl.c                             |  6 +++
 run-command.c                             |  8 +++-
 run-command.h                             |  5 ++-
 t/t5616-partial-clone.sh                  | 54 ++++++++++++++++++++++-
 transport-helper.c                        |  3 ++
 transport.c                               |  4 ++
 transport.h                               |  4 ++
 20 files changed, 186 insertions(+), 29 deletions(-)

base-commit: dab1b7905d0b295f1acef9785bb2b9cbb0fdec84

Submitted-As: https://lore.kernel.org/git/pull.1138.v2.git.1645719218.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.1138.git.1643730593.gitgitgadget@gmail.com