--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/git_serve.py	Sat Feb 14 18:41:52 2026 -0500
@@ -0,0 +1,235 @@
+from __future__ import annotations
+
+import binascii
+import email.parser
+import email.policy
+import os
+import pathlib
+import re
+import shutil
+import subprocess
+import threading
+import typing as t
+
+import dulwich.refs
+import mercurial.error as hgerr
+from mercurial import extensions
+from mercurial import registrar
+from mercurial import wireprotoserver
+
+if t.TYPE_CHECKING:
+    import hggit.git_handler
+    import mercurial.hgweb.hgweb_mod_inner as web_inner
+    import mercurial.hgweb.request as hgreq
+    import mercurial.interfaces.repository as hgrepo
+    import mercurial.ui as hgui
+
+    class GittyRepo(hgrepo.IRepo, t.Protocol):
+        githandler: hggit.git_handler.GitHandler
+
+    PermissionCheck = t.Callable[
+        [web_inner.requestcontext, hgreq.parsedrequest, bytes],
+        None,
+    ]
+    GitPrelude = t.Sequence[bytes | str | os.PathLike]
+
+
+_CGI_VAR = re.compile(rb'[A-Z0-9_]+$')
+"""Environment variables that we need to pass to git-as-cgi."""
+
+
+def _build_git_environ(
+    req_ctx: web_inner.requestcontext,
+    request: hgreq.parsedrequest,
+) -> dict[bytes, bytes]:
+    """Builds the environment to be sent to Git to serve HTTP."""
+    fixed = {
+        k: v
+        for (k, v) in request.rawenv.items()
+        if isinstance(v, bytes) and _CGI_VAR.match(k)
+    }
+    fixed[b'GIT_HTTP_EXPORT_ALL'] = b'yes'
+    fixed[b'GIT_PROJECT_ROOT'] = req_ctx.repo.path
+    fixed[b'PATH_INFO'] = b'/git/' + request.dispatchpath
+    return fixed
+
+
+def _parse_cgi_response(
+    output: t.IO[bytes],
+) -> tuple[bytes, dict[bytes, bytes], t.IO[bytes]]:
+    parser = email.parser.BytesFeedParser(policy=email.policy.HTTP)
+    while line := output.readline():
+        if not line.rstrip(b'\r\n'):
+            # We've reached the end of the headers.
+            # Leave the rest in the output for later.
+            break
+        parser.feed(line)
+    msg = parser.close()
+    status = msg.get('Status', '200 OK I guess').encode('utf-8')
+    del msg['Status']  # this won't raise an exception
+    byte_headers = {
+        k.encode('utf-8'): v.encode('utf-8') for (k, v) in msg.items()
+    }
+    return status, byte_headers, output
+
+
+_feeds = 0
+_feeder_lock = threading.Lock()
+
+
+def feed_count() -> int:
+    global _feeds
+    with _feeder_lock:
+        _feeds += 1
+        return _feeds
+
+
+def git_binary(ui: hgui.ui) -> bytes:
+    return ui.config(b'git-serve', b'git', default=b'git')
+
+
+def handle_git_protocol(
+    original: t.Callable[..., bool],
+    req_ctx: web_inner.requestcontext,
+    request: hgreq.parsedrequest,
+    response: hgreq.wsgiresponse,
+    check_permission: PermissionCheck,
+) -> bool:
+    repo = req_ctx.repo
+    if not is_gitty(repo) or b'git-protocol' not in request.headers:
+        # We only handle Git requests; everything else is normal.
+        return original(req_ctx, request, response, check_permission)
+    check_permission(req_ctx, request, b'pull')
+    # If a request is git, we assume we should be the one handling it.
+    cgi_env = _build_git_environ(req_ctx, request)
+    http_backend = req_ctx.repo.ui.configlist(
+        b'git-serve', b'http-backend', default=(b'git', b'http-backend')
+    )
+    is_post = request.method == b'POST'
+    call = subprocess.Popen(
+        http_backend,
+        close_fds=True,
+        stdin=subprocess.PIPE if is_post else None,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.DEVNULL,
+        env=cgi_env,
+        text=False,
+    )
+    assert call.stdout
+
+    def feed():
+        try:
+            with call.stdin as stdin:
+                shutil.copyfileobj(request.bodyfh, stdin)
+        except (OSError, BrokenPipeError):
+            pass  # Expected; this just means it's closed.
+
+    if is_post:
+        threading.Thread(target=feed, name=f'git-feeder-{feed_count()}').start()
+    status, headers, rest = _parse_cgi_response(call.stdout)
+    response.status = status
+    for k, v in headers.items():
+        response.headers[k] = v
+
+    def write_the_rest():
+        with call, rest:
+            while more := rest.read(64 * 1024):
+                yield more
+
+    response.setbodygen(write_the_rest())
+    response.sendresponse()
+    return True
+
+
+def clean_all_refs(refs: dulwich.refs.RefsContainer) -> None:
+    for ref in refs.allkeys():
+        refs.remove_if_equals(ref, None)
+
+
+def set_head(repo: GittyRepo) -> None:
+    """Creates a HEAD reference in Git referring to the current HEAD."""
+    # By default, we use '@', since that's what will be auto checked out.
+    current = b'@'
+    if current not in repo._bookmarks:
+        current = repo._bookmarks.active or current
+
+    # We'll be moving this (possibly fake) bookmark into Git.
+    git_current = current
+    if current == b'@':
+        # @ is a special keyword in Git, so we can't use it as a bookmark.
+        git_current = b'__default__'
+    git_branch = dulwich.refs.LOCAL_BRANCH_PREFIX + git_current
+    if not dulwich.refs.check_ref_format(git_branch):
+        # We can't export this ref to Git. Give up.
+        return
+    refs = repo.githandler.git.refs
+    if git_branch not in refs:
+        # This means our bookmark isn't actually in Git (usually because
+        # there's no real bookmark called '@'). We need to fake it.
+        try:
+            # Maybe this is a real bookmark?
+            hgsha = repo._bookmarks[current]
+        except KeyError:
+            # Not a real bookmark. Assume we want the tip of the current branch.
+            branch = repo.dirstate.branch()
+            try:
+                tip = repo.branchtip(branch)
+            except hgerr.RepoLookupError:
+                # This branch somehow doesn't exist???
+                return
+            hgsha = binascii.hexlify(tip)
+        gitsha = repo.githandler.map_git_get(hgsha)
+        if not gitsha:
+            # No Git SHA to match this Hg sha. Give up.
+            return
+        refs.add_packed_refs({git_branch: gitsha})
+    refs.set_symbolic_ref(b'HEAD', git_branch)
+
+
+def export_hook(ui: hgui.ui, repo: GittyRepo, **__: object) -> None:
+    never_export = ui.configbool(b'git-serve', b'never-export')
+    if never_export:
+        return
+    git_repo = pathlib.Path(repo.githandler.gitdir)
+    always_export = ui.configbool(b'git-serve', b'always-export', False)
+    if always_export or git_repo.exists():
+        export_repo(repo)
+
+
+def export_repo(repo: GittyRepo) -> None:
+    clean_all_refs(repo.githandler.git.refs)
+    repo.githandler.export_commits()
+    set_head(repo)
+
+
+def is_gitty(repo: hgrepo.IRepo) -> t.TypeGuard[GittyRepo]:
+    return hasattr(repo, 'githandler')
+
+
+# Interfacing with Mercurial
+
+__version__ = '0.1'
+
+cmdtable: dict[bytes, object] = {}
+
+command = registrar.command(cmdtable)
+
+
+@command(b'git-serve-export')
+def git_serve_export(_: hgui.ui, repo: hgrepo.IRepo, **__: object) -> None:
+    if not is_gitty(repo):
+        raise hgerr.Abort(b'this extension depends on the `hggit` extension')
+    export_repo(repo)
+
+
+def uisetup(_: hgui.ui) -> None:
+    extensions.wrapfunction(
+        wireprotoserver, 'handlewsgirequest', handle_git_protocol
+    )
+
+
+def reposetup(ui: hgui.ui, _: hgrepo.IRepo) -> None:
+    ui.setconfig(b'hooks', b'txnclose.__gitserve_internal__', export_hook)
+
+
+__all__ = ('__version__', 'cmdtable', 'command', 'uisetup', 'reposetup')