Shallow clones don't seem to work for local clones

[ehuss]

From what I can tell, shallow clones don't seem to work with local clones. Am I missing some option? I'm guessing they only work with the smart transport. I would expect it to work like the git CLI, which can support shallow clones when using file:// URLs.

git clone --depth=1 file:///path/to/test

Reproduction steps

#include <assert.h>
#include <git2/repository.h>
#include <git2/errors.h>
#include <git2/global.h>
#include <git2/signature.h>
#include <git2/index.h>
#include <git2/commit.h>
#include <git2/clone.h>
#include <git2/diff.h>
#include <stdio.h>
#include <unistd.h>

int main() {
  assert(git_libgit2_init() == 1);

  git_repository *repo;
  assert(git_repository_init(&repo, "repo", 0) == 0);

  FILE *fp;
  fp = fopen("repo/file", "w");
  fputs("this is a test\n", fp);
  fclose(fp);

  git_index *index;
  assert(git_repository_index(&index, repo) == 0);
  assert(git_index_add_bypath(index, "file") == 0);
  assert(git_index_write(index) == 0);

  git_oid tree_id;
  git_tree *tree;
  assert(git_index_write_tree(&tree_id, index) == 0);
  assert(git_tree_lookup(&tree, repo, &tree_id) == 0);
  git_signature *sig;
  assert(git_signature_default(&sig, repo) == 0);
  git_oid first_commit_id;
  assert(git_commit_create_v(&first_commit_id, repo, "HEAD", sig, sig, NULL, "first", tree, 0) == 0);

  truncate("repo/file", 0);
  assert(git_repository_index(&index, repo) == 0);
  assert(git_index_add_bypath(index, "file") == 0);
  assert(git_index_write(index) == 0);
  assert(git_tree_lookup(&tree, repo, &tree_id) == 0);
  git_oid second_commit_id;
  assert(git_commit_create_v(&second_commit_id, repo, "HEAD", sig, sig, NULL, "second", tree, 1, first_commit_id) == 0);

  git_repository *repo2;
  git_clone_options clone_opts = GIT_CLONE_OPTIONS_INIT;
  clone_opts.fetch_opts.depth = 1;
  // It doesn't seem to matter how `local` is set.
  clone_opts.local = GIT_CLONE_LOCAL_NO_LINKS;
  assert(git_clone(&repo2, "repo", "repo2", &clone_opts) == 0);

  assert(git_repository_is_shallow(repo2) == 1);

  return 0;
}

Expected behavior

Local repos can be shallow cloned.

Actual behavior

It seems to ignore the depth parameter.

Version of libgit2 (release number or SHA1)

4939fa7

Operating system(s) tested

macOS

[ethomson]

Yes, there's a lot of disappointment all around in local remotes. git will either invoke git-upload-pack and git-receive-pack or do some hardlinking magic, depending on how you specify the local path. (file:///tmp/foo behaves differently than /tmp/foo).

We do neither of those things. We open up the remote as our own object database and sling files over. I think that this is in many ways a very clever solution, but as capabilities are added to the smart protocol, it would mean that they would need to be independently implemented in the local transport, which is a bummer.

I've coincidentally been playing around with refactoring the smart protocol handling a bit - and the local transport has been my test case for it - invoking git-upload-pack and using the smart protocol. That would get us parity between https/ssh and local. I can try to get it into a state where I can push it up this weekend.

[ethomson]

In the meantime, should the depth parameter error on local transports? That seems more polite than ignoring it.

[ethomson]

We now error on depth with local transports (with #6757). Actually making this work is something that I've started on, but is a (much) bigger dig.