From: Derrick Stolee <dstolee@xxxxxxxxxxxxx> The partial clone feature has several modes, but only a few are quick for a server to process using reachability bitmaps: * Blobless: --filter=blob:none downloads all commits and trees and fetches necessary blobs on-demand. * Treeless: --filter=tree:0 downloads all commits and fetches necessary trees and blobs on demand. This treeles mode is most similar to a shallow clone in the total size (it only adds the commit objects for the full history). This makes treeless clones an interesting replacement for shallow clones. A user can run more commands in a treeless clone than in a shallow clone, especially 'git log' (no pathspec). In particular, servers can still serve 'git fetch' requests quickly by calculating the difference between commit wants and haves using bitmaps. I was testing this feature with this in mind, and I knew that some trees would be downloaded multiple times when checking out a new branch, but I did not expect to discover a significant issue with 'git fetch', at least in repostiories with submodules. I was testing these commands: $ git clone --filter=tree:0 --single-branch --branch=master \ https://github.com/git/git $ git -C git fetch origin "+refs/heads/*:refs/remotes/origin/*" This fetch command started downloading several pack-files of trees before completing the command. I never let it finish since I got so impatient with the repeated downloads. During debugging, I found that the stack triggering promisor_remote_get_direct() was going through fetch_populated_submodules(). Notice that I did not recurse my submodules in the original clone, so the sha1collisiondetection submodule is not initialized. Even so, my 'git fetch' was scanning commits for updates to submodules. I decided that even if I did populate the submodules, the nature of treeless clones makes me not want to care about the contents of commits other than those that I am explicitly navigating to. This loop of tree fetches can be avoided by adding --no-recurse-submodules to the 'git fetch' command or setting fetch.recurseSubmodules=no. To make this as painless as possible for future users of treeless clones, automatically set fetch.recurseSubmodules=no at clone time. Signed-off-by: Derrick Stolee <dstolee@xxxxxxxxxxxxx> --- clone: --filter=tree:0 implies fetch.recurseSubmodules=no While testing different partial clone options, I stumbled across this one. My initial thought was that we were parsing commits and loading their root trees unnecessarily, but I see that doesn't happen after this change. Here are some recent discussions about using --filter=tree:0: [1] https://lore.kernel.org/git/aa7b89ee-08aa-7943-6a00-28dcf344426e@xxxxxxxxxxx/ [2] https://lore.kernel.org/git/cover.1588633810.git.me@xxxxxxxxxxxx/[3] https://lore.kernel.org/git/58274817-7ac6-b6ae-0d10-22485dfe5e0e@xxxxxxxxxxx/ Thanks, -Stolee Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-797%2Fderrickstolee%2Ftree-0-v1 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-797/derrickstolee/tree-0-v1 Pull-Request: https://github.com/gitgitgadget/git/pull/797 list-objects-filter-options.c | 4 ++++ t/t5616-partial-clone.sh | 6 ++++++ 2 files changed, 10 insertions(+) diff --git a/list-objects-filter-options.c b/list-objects-filter-options.c index defd3dfd10..249939dfa5 100644 --- a/list-objects-filter-options.c +++ b/list-objects-filter-options.c @@ -376,6 +376,10 @@ void partial_clone_register( expand_list_objects_filter_spec(filter_options)); free(filter_name); + if (filter_options->choice == LOFC_TREE_DEPTH && + !filter_options->tree_exclude_depth) + git_config_set("fetch.recursesubmodules", "no"); + /* Make sure the config info are reset */ promisor_remote_reinit(); } diff --git a/t/t5616-partial-clone.sh b/t/t5616-partial-clone.sh index f4d49d8335..b2eaf78069 100755 --- a/t/t5616-partial-clone.sh +++ b/t/t5616-partial-clone.sh @@ -341,6 +341,12 @@ test_expect_success 'partial clone with sparse filter succeeds' ' ) ' +test_expect_success '--filter=tree:0 sets fetch.recurseSubmodules=no' ' + rm -rf dst && + git clone --filter=tree:0 "file://$(pwd)/src" dst && + test_config -C dst fetch.recursesubmodules no +' + test_expect_success 'partial clone with unresolvable sparse filter fails cleanly' ' rm -rf dst.git && test_must_fail git clone --no-local --bare \ base-commit: faefdd61ec7c7f6f3c8c9907891465ac9a2a1475 -- gitgitgadget
