Closes #1464: Add support for libgit2's custom_headers

[beamerblvd]

Feedback welcome of course, and also this may need more work, because I do not know how to write an automated test for this. An automated test rather depends on having a remote that requires a specific header and fails without it (my particular use case), which isn't really amenable to an automated test. I would love thoughts on approaches I could take. Otherwise, the existing pytest suite, mypy, ruff, and subtests pass.

Manual test:

In [1]: import pathlib, pygit2

In [2]: from typing import override

In [3]: class BitbucketCallbacks(pygit2.RemoteCallbacks):
   ...:     @override
   ...:     def custom_headers(self) -> list[str] | None:
   ...:         return ["Authorization: Bearer BBDC-abc123def456ghi789+"]
   ...: 

In [4]: clone_dir = pathlib.Path("./bs_clone").resolve()

In [5]: clone_dir
Out[5]: PosixPath('/foo/bar/baz/bs_clone')

In [6]: repo = pygit2.clone_repository(url="https://www.example.com/bitbucket/scm/project/repo.git", path=clone_dir, callbacks=BitbucketCallbacks())

In [7]: repo
Out[7]: pygit2.Repository('/foo/bar/baz/bs_clone/.git/')

In [9]: list(repo.branches)
Out[9]: 
['main-3.4.0',
 'origin/1',
 'origin/1.0.0',
 ...]

In [10]: branch = repo.branches.local.create("nicktest-3.4.0", repo[repo.branches["main-3.4.0"].target])

In [11]: branch.is_checked_out()
Out[11]: False

In [14]: repo.set_head(branch.name)

In [15]: branch.is_checked_out()
Out[15]: True

In [16]: (clone_dir / "nicktest.txt").write_text("testing 1 2 3\n")
Out[16]: 13

In [17]: repo.status()
Out[17]: {'nicktest.txt': <FileStatus.WT_NEW: 128>}

In [19]: repo.index.add("nicktest.txt")

In [20]: repo.index.write()

In [21]: repo.status()
Out[21]: {'nicktest.txt': <FileStatus.INDEX_NEW: 1>}

In [22]: tree_id = repo.index.write_tree()

In [23]: author = pygit2.Signature('Nick Williams', 'nick.williams@example.com')

In [24]: parents = [repo.head.target]

In [25]: commit_id = repo.create_commit("HEAD", author, author, "#1234: This is just a test", tree_id, parents)

In [30]: repo.remotes["origin"].push([f"{repo.head.name}:{repo.head.name}"], callbacks=BitbucketCallbacks())

In [31]: branch.upstream = repo.branches.remote["origin/nicktest-3.4.0"]

In [32]: branch.upstream_name
Out[32]: 'refs/remotes/origin/nicktest-3.4.0'

In [37]: repo.status()
Out[37]: {}

In [38]: repo.remotes["origin"].fetch(callbacks=BitbucketCallbacks())
Out[38]: <pygit2.remotes.TransferProgress at 0x11127d5d0>

In [39]: heads = repo.remotes["origin"].list_heads(callbacks=BitbucketCallbacks())

In [40]: [head.name for head in heads]
Out[40]: 
['HEAD',
 'refs/heads/1',
 'refs/heads/1.0.0',
 ...,
 'refs/heads/main-3.4.0',
 'refs/heads/nicktest-3.4.0',
 ...]

[jdavid]

A full test will be difficult, maybe we can do something simple, AI suggested this...

Test that the headers are correctly copied into the C structs, similar to test_push_options in test/test_remote.py. Example:

def test_custom_headers(origin, clone, remote):
    class MyCallbacks(pygit2.RemoteCallbacks):
        def custom_headers(self):
            return ['Authorization: Bearer token', 'X-Other: foo']

    callbacks = MyCallbacks()
    remote.push(['refs/heads/master'], callbacks)
    assert callbacks.push_options.custom_headers.count == 2 

A corresponding fetch/connect test would also be valuable.