cmd/git(fix[Git.fetch,Git.pull]): Remove clone-only branch/origin params

why: The --branch and --origin flags only exist for git clone, not for
git fetch or git pull. Using these parameters would cause git to fail
with "unknown option 'branch'" or "unknown option 'origin'".
what:
- Remove branch and origin parameters from fetch() signature
- Remove branch and origin parameters from pull() signature
- Remove implementation code that emitted these invalid flags

Author: tony

src/libvcs/cmd/git.py

@@ -423,8 +423,6 @@ def fetch(
         reftag: t.Any | None = None,
         deepen: str | None = None,
         depth: str | None = None,
-        branch: str | None = None,
-        origin: str | None = None,
         upload_pack: str | None = None,
         shallow_since: str | None = None,
         shallow_exclude: str | None = None,
@@ -496,10 +494,6 @@ def fetch(
             local_flags.append(f"--filter={_filter}")
         if depth is not None:
             local_flags.extend(["--depth", depth])
-        if branch is not None:
-            local_flags.extend(["--branch", branch])
-        if origin is not None:
-            local_flags.extend(["--origin", origin])
         if upload_pack is not None:
             local_flags.extend(["--upload-pack", upload_pack])
         if shallow_since is not None:
@@ -780,8 +774,6 @@ def pull(
         repository: str | None = None,
         deepen: str | None = None,
         depth: str | None = None,
-        branch: str | None = None,
-        origin: str | None = None,
         upload_pack: str | None = None,
         shallow_since: str | None = None,
         shallow_exclude: str | None = None,
@@ -975,10 +967,6 @@ def pull(
             local_flags.append(f"--filter={_filter}")
         if depth is not None:
             local_flags.extend(["--depth", depth])
-        if branch is not None:
-            local_flags.extend(["--branch", branch])
-        if origin is not None:
-            local_flags.extend(["--origin", origin])
         if upload_pack is not None:
             local_flags.extend(["--upload-pack", upload_pack])
         if shallow_since is not None: