git_fetch: Optional initialization/update of Git submodules

prelude/decls/git_rules.bzl

@@ -43,6 +43,12 @@ git_fetch = prelude_rule(
             "rev": attrs.string(doc = """
                 Commit hash. 40 hex digits for sha1, 64 hex digits for sha256.
             """),
+            "update_submodules": attrs.bool(
+                default = False,
+                doc = """
+                Whether to initialize and update Git submodules after there worktree checkout.
+                """
+            ),
             "sub_targets": attrs.list(
                 attrs.string(),
                 default = [],

prelude/git/git_fetch.bzl

@@ -38,12 +38,18 @@ def git_fetch_impl(ctx: AnalysisContext) -> list[Provider]:
         short_path = "work-tree"
     work_tree = ctx.actions.declare_output(short_path, dir = True)
 
+    if ctx.attrs.update_submodules:
+        update_submodules = cmd_args("--update-submodules")
+    else:
+        update_submodules = cmd_args()
+
     cmd = [
         ctx.attrs._git_fetch_tool[RunInfo],
         cmd_args("--git-dir=", git_dir.as_output(), delimiter = ""),
         cmd_args("--work-tree=", work_tree.as_output(), delimiter = ""),
         cmd_args("--repo=", ctx.attrs.repo, delimiter = ""),
         cmd_args("--rev=", rev, delimiter = ""),
+        update_submodules,
     ]
     if object_format != None:
         cmd.append(cmd_args("--object-format=", object_format, delimiter = ""))

prelude/git/tools/git_fetch.py

@@ -7,6 +7,7 @@
 # above-listed licenses.
 
 import argparse
+import os
 import subprocess
 import sys
 import time
@@ -51,13 +52,15 @@ class Args(NamedTuple):
     object_format: ObjectFormat
     repo: str
     rev: str
+    update_submodules: bool
 
 
 def arg_parse() -> Args:
     parser = argparse.ArgumentParser()
     parser.add_argument("--git-dir", type=Path, required=True)
     parser.add_argument("--work-tree", type=Path, required=True)
     parser.add_argument("--object-format", type=ObjectFormat, required=False)
+    parser.add_argument("--update-submodules", action='store_true', required=False)
     parser.add_argument("--repo", type=str, required=True)
     parser.add_argument("--rev", type=str, required=True)
     return Args(**vars(parser.parse_args()))
@@ -76,7 +79,7 @@ def main() -> None:
 
     args.work_tree.mkdir(exist_ok=True)
 
-    git = ["git", f"--git-dir={args.git_dir}", f"--work-tree={args.work_tree}"]
+    git = ["git", "--git-dir", args.git_dir, "--work-tree", args.work_tree]
     if args.object_format is None:
         object_format_args = []
     else:
@@ -97,6 +100,10 @@ def main() -> None:
 
     run([*git, "checkout", "FETCH_HEAD"], check=True)
 
+    if args.update_submodules:
+        git_in_worktree = ["git", "--git-dir", os.path.abspath(args.git_dir), "-C", args.work_tree]
+        run([*git_in_worktree, "submodule", "update", "--init"], check=True)
+
 
 if __name__ == "__main__":
     main()