On 08/29, Jonathan Nieder wrote: > Hi, > > Most of the credit for this series should go to Stefan Beller. I just > decided to pull the trigger on sending out what we have so far. > > This series is about API. It makes no functional change yet. > > Today, when a git command wants to operate on some objects from another > repository (e.g., a submodule), it has two choices: > > A. Use run_command to operate on that repository in a separate process. > > B. Use add_to_alternates_memory to pretend the repository is an > alternate. This has a number of downsides. Aside from aesthetics, > one particularly painful consequence is that as alternates > accumulate, the number of packs git has to check for objects > increases, which can cause significant slowdowns. > > Brandon Williams's recent work to introduce "struct repository" points > to a better way. Encapsulating object access in struct repository > would mean: > > i. The API for accessing objects in another repository becomes more > simple and familiar (instead of using the CLI or abusing alternates). > > ii. Operations on one repository do not interfere with another, > neither in semantics (e.g. replace objects do not work correctly > with the approach (B) above) nor performance (already described > above). > > iii. Resources associated with access to a repository could be freed > when done with that repo. > > iv. Thread-safe multiple readers to a single repository also become > straightforward, by using multiple repository objects for the same > repo. > > This series is a small step in that direction. > > At the end of this series, sha1_loose_object_info takes a repository > argument and can be independently called for multiple repositories. > Not incredibly useful on its own, but a future series will do the same > for sha1_object_info, which will be enough to migrate a caller in > submodule.c (which uses the object store for commit existence checks). > > This series has a few phases: > > 1. Patch 1 is a cleanup that made some of the later patches easier. > > 2. Patches 2-6 create a struct object_store field inside struct > repository and move some globals to it. > > 3. Patches 7-24 are mechanical changes that update some functions to > accept a repository argument. The only goal is to make the later > patches that teach these functions to actual handle a repository > other than the_repository easier to review. The patches enforce > at compile time that no caller passes a repository other than > the_repository --- see patch 7 in particular for details on how > that works. > > 4. Patches 25-39 update the implementations of those functions to > handle a repository other than the_repository. This means the > safety check introduced in phase 3 goes away completely --- all > functions that gained a repository argument are safe to use with > a repository argument other than the_repository. > > Patches 2-6 and 25-39 should be the most interesting to review. I'd > particularly appreciate if people can look over 25-39 carefully. We > were careful not to leave any calls to functions that assume they are > operating on the_repository, but a triple-check is always welcome. > > Thanks as well to brian m. carlson, who showed us how such a long and > potentially tedius series can be made bearable for reviewers. > > Thoughts of all kinds welcome, as always. Just finished looking through the series. Thanks for keeping each commit very short and to the point, it made reviewing it much easier. I couldn't see anything wrong these transformations and I am very happy to see this work getting done. One thing that needs to be noted is that currently the object_store is only really being used by the_repository so this series didn't need to create any object_store_init() or object_store_clear() type functions. So these types of functions will need to be added once submodules are using their own object store, in their own struct repository. > > Thanks, > Jonathan Nieder (24): > pack: make packed_git_mru global a value instead of a pointer > object-store: move packed_git and packed_git_mru to object store > struct > pack: move prepare_packed_git_run_once to object store struct > pack: move approximate object count to object store struct > pack: add repository argument to install_packed_git > pack: add repository argument to prepare_packed_git_one > pack: add repository argument to rearrange_packed_git > pack: add repository argument to prepare_packed_git_mru > pack: add repository argument to prepare_packed_git > pack: add repository argument to reprepare_packed_git > pack: add repository argument to sha1_file_name > pack: add repository argument to map_sha1_file > pack: allow install_packed_git to handle arbitrary repositories > pack: allow rearrange_packed_git to handle arbitrary repositories > pack: allow prepare_packed_git_mru to handle arbitrary repositories > pack: allow prepare_packed_git_one to handle arbitrary repositories > pack: allow prepare_packed_git to handle arbitrary repositories > pack: allow reprepare_packed_git to handle arbitrary repositories > pack: allow sha1_file_name to handle arbitrary repositories > pack: allow stat_sha1_file to handle arbitrary repositories > pack: allow open_sha1_file to handle arbitrary repositories > pack: allow map_sha1_file_1 to handle arbitrary repositories > pack: allow map_sha1_file to handle arbitrary repositories > pack: allow sha1_loose_object_info to handle arbitrary repositories > > Stefan Beller (15): > repository: introduce object store field > object-store: move alt_odb_list and alt_odb_tail to object store > struct > sha1_file: add repository argument to alt_odb_usable > sha1_file: add repository argument to link_alt_odb_entry > sha1_file: add repository argument to read_info_alternates > sha1_file: add repository argument to link_alt_odb_entries > sha1_file: add repository argument to stat_sha1_file > sha1_file: add repository argument to open_sha1_file > sha1_file: add repository argument to map_sha1_file_1 > sha1_file: add repository argument to sha1_loose_object_info > object-store: add repository argument to prepare_alt_odb > object-store: add repository argument to foreach_alt_odb > sha1_file: allow alt_odb_usable to handle arbitrary repositories > object-store: allow prepare_alt_odb to handle arbitrary repositories > object-store: allow foreach_alt_odb to handle arbitrary repositories > > builtin/count-objects.c | 10 ++- > builtin/fsck.c | 15 ++-- > builtin/gc.c | 8 +- > builtin/index-pack.c | 1 + > builtin/pack-objects.c | 23 +++-- > builtin/pack-redundant.c | 8 +- > builtin/receive-pack.c | 4 +- > builtin/submodule--helper.c | 4 +- > bulk-checkin.c | 3 +- > cache.h | 50 ++--------- > contrib/coccinelle/packed_git.cocci | 15 ++++ > fast-import.c | 10 ++- > fetch-pack.c | 3 +- > http-backend.c | 8 +- > http-push.c | 1 + > http-walker.c | 4 +- > http.c | 9 +- > mru.h | 1 + > object-store.h | 71 ++++++++++++++++ > pack-bitmap.c | 6 +- > pack-check.c | 1 + > pack-revindex.c | 1 + > packfile.c | 94 ++++++++++---------- > packfile.h | 6 +- > reachable.c | 1 + > repository.c | 4 +- > repository.h | 7 ++ > server-info.c | 8 +- > sha1_file.c | 165 ++++++++++++++++++++---------------- > sha1_name.c | 11 ++- > streaming.c | 5 +- > transport.c | 4 +- > 32 files changed, 344 insertions(+), 217 deletions(-) > create mode 100644 contrib/coccinelle/packed_git.cocci > create mode 100644 object-store.h > > -- > 2.14.1.581.gf28d330327 > -- Brandon Williams
