feat(release): bump the root crate in Cargo.toml and Cargo.lock

A repo whose Cargo.toml has a [package] section now gets its version set to the release version, and the matching local [[package]] entry in Cargo.lock (same name, no source line) follows in the same release commit, so cargo build --locked keeps passing. Workspaces without [package] and repos without Cargo.toml release as before; a Cargo.lock without the local entry aborts the release before any file is written.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/pkgmgr/actions/release/files/__init__.py

@@ -10,6 +10,7 @@ Keep this package stable so existing imports continue to work, e.g.:
 
 from __future__ import annotations
 
+from .cargo import update_cargo_version
 from .changelog_md import update_changelog
 from .debian import _get_debian_author, update_debian_changelog
 from .editor import _open_editor_for_changelog
@@ -22,6 +23,7 @@ from .rpm_spec import update_spec_version
 __all__ = [
     "_get_debian_author",
     "_open_editor_for_changelog",
+    "update_cargo_version",
     "update_changelog",
     "update_debian_changelog",
     "update_flake_version",

src/pkgmgr/actions/release/files/cargo.py

@@ -0,0 +1,76 @@
+from __future__ import annotations
+
+import os
+import re
+
+
+def _read(path: str) -> str:
+    with open(path, encoding="utf-8") as f:
+        return f.read()
+
+
+def _write(path: str, content: str) -> None:
+    with open(path, "w", encoding="utf-8") as f:
+        f.write(content)
+
+
+def update_cargo_version(
+    repo_root: str, new_version: str, preview: bool = False
+) -> list[str]:
+    """
+    Set the root crate's version in Cargo.toml and its entry in Cargo.lock.
+
+    Args:
+        repo_root: repository root that may hold Cargo.toml and Cargo.lock.
+        new_version: release version without the leading "v".
+        preview: only print what would change.
+
+    Returns:
+        The paths that were (or in preview would be) changed.
+    """
+    toml_path = os.path.join(repo_root, "Cargo.toml")
+    if not os.path.exists(toml_path):
+        print("[INFO] No Cargo.toml found. Skipping Cargo version update.")
+        return []
+
+    toml = _read(toml_path)
+    block = re.search(r"(?ms)^\[package\]\s*$.*?(?=^\s*\[|\Z)", toml)
+    if not block:
+        print("[INFO] Cargo.toml has no [package] section. Skipping.")
+        return []
+
+    name = re.search(r'(?m)^\s*name\s*=\s*"([^"]+)"', block.group(0))
+    if not name:
+        raise RuntimeError("Missing name key in [package] section of Cargo.toml")
+    new_block, count = re.subn(
+        r'(?m)^(\s*version\s*=\s*")[^"]+(")',
+        lambda m: f"{m.group(1)}{new_version}{m.group(2)}",
+        block.group(0),
+        count=1,
+    )
+    if count == 0:
+        raise RuntimeError("Missing version key in [package] section of Cargo.toml")
+    changes = {toml_path: toml[: block.start()] + new_block + toml[block.end() :]}
+
+    lock_path = os.path.join(repo_root, "Cargo.lock")
+    if os.path.exists(lock_path):
+        lock, count = re.subn(
+            rf'(?m)^(\[\[package\]\]\nname = "{re.escape(name.group(1))}"\n'
+            r'version = ")[^"]+("\n)(?!source = )',
+            lambda m: f"{m.group(1)}{new_version}{m.group(2)}",
+            _read(lock_path),
+        )
+        if count != 1:
+            raise RuntimeError(
+                f"Expected one local {name.group(1)!r} package in Cargo.lock, "
+                f"found {count}"
+            )
+        changes[lock_path] = lock
+
+    for path, content in changes.items():
+        if preview:
+            print(f"[PREVIEW] Would update {path} version to {new_version}")
+        else:
+            _write(path, content)
+            print(f"Updated {path} version to {new_version}")
+    return list(changes)

src/pkgmgr/actions/release/workflow.py

@@ -10,6 +10,7 @@ from pkgmgr.core.git.queries import get_current_branch
 from pkgmgr.core.repository.paths import resolve_repo_paths
 
 from .files import (
+    update_cargo_version,
     update_changelog,
     update_debian_changelog,
     update_flake_version,
@@ -74,6 +75,8 @@ def _release_impl(
 
     update_flake_version(paths.flake_nix, new_ver_str, preview=preview)
 
+    cargo_files = update_cargo_version(repo_root, new_ver_str, preview=preview)
+
     if paths.arch_pkgbuild:
         update_pkgbuild_version(paths.arch_pkgbuild, new_ver_str, preview=preview)
     else:
@@ -124,6 +127,7 @@ def _release_impl(
         paths.arch_pkgbuild,
         paths.rpm_spec,
         paths.debian_changelog,
+        *cargo_files,
     ]
     existing_files = [
         p for p in files_to_add if isinstance(p, str) and p and os.path.exists(p)