Bazel: Add lfs_archives function

misc/bazel/lfs.bzl

@@ -28,29 +28,42 @@ def lfs_smudge(repository_ctx, srcs, *, extract = False, stripPrefix = None, exe
             res = repository_ctx.download([], src.basename, sha256 = info, allow_fail = True, executable = executable)
             if not res.success:
                 remote.append(src)
-        if remote:
-            infos = probe(remote)
-            for src, info in zip(remote, infos):
-                sha256, _, url = info.partition(" ")
-                repository_ctx.report_progress("downloading remote %s" % src.basename)
-                repository_ctx.download(url, src.basename, sha256 = sha256, executable = executable)
-        if extract:
-            for src in srcs:
-                repository_ctx.report_progress("extracting %s" % src.basename)
-                repository_ctx.extract(src.basename, stripPrefix = stripPrefix)
-                repository_ctx.delete(src.basename)
+    if remote:
+        infos = probe(remote)
+        for src, info in zip(remote, infos):
+            sha256, _, url = info.partition(" ")
+            repository_ctx.report_progress("downloading remote %s" % src.basename)
+            repository_ctx.download(url, src.basename, sha256 = sha256, executable = executable)
+    if extract:
+        for src in srcs:
+            repository_ctx.report_progress("extracting %s" % src.basename)
+            repository_ctx.extract(src.basename, stripPrefix = stripPrefix)
+            repository_ctx.delete(src.basename)
 
-def _download_and_extract_lfs(repository_ctx):
+def _add_build_file(repository_ctx):
     attr = repository_ctx.attr
-    src = repository_ctx.path(attr.src)
     if attr.build_file_content and attr.build_file:
         fail("You should specify only one among build_file_content and build_file for rule @%s" % repository_ctx.name)
-    lfs_smudge(repository_ctx, [src], extract = True, stripPrefix = attr.strip_prefix)
     if attr.build_file_content:
         repository_ctx.file("BUILD.bazel", attr.build_file_content)
     elif attr.build_file:
         repository_ctx.symlink(attr.build_file, "BUILD.bazel")
 
+def _download_and_extract_lfs_archive(repository_ctx):
+    attr = repository_ctx.attr
+    lfs_smudge(repository_ctx, [repository_ctx.path(attr.src)], extract = True, stripPrefix = attr.strip_prefix)
+    _add_build_file(repository_ctx)
+
+def _download_and_extract_lfs_archives(repository_ctx):
+    for src in repository_ctx.attr.srcs:
+        lfs_smudge(
+            repository_ctx,
+            [repository_ctx.path(src)],
+            extract = True,
+            stripPrefix = repository_ctx.attr.strip_prefix,
+        )
+    _add_build_file(repository_ctx)
+
 def _download_lfs(repository_ctx):
     attr = repository_ctx.attr
     if int(bool(attr.srcs)) + int(bool(attr.dir)) != 1:
@@ -83,18 +96,30 @@ def _download_lfs(repository_ctx):
         'alias(name = "file", actual = "//:%s", visibility = ["//visibility:public"])\n' % name,
     )
 
+_lfs_archive_attrs = {
+    "build_file": attr.label(doc = "The file to use as the BUILD file for this repository. " +
+                                   "Either build_file or build_file_content can be specified, but not both."),
+    "build_file_content": attr.string(doc = "The content for the BUILD file for this repository. " +
+                                            "Either build_file or build_file_content can be specified, but not both."),
+    "strip_prefix": attr.string(default = "", doc = "A directory prefix to strip from the extracted files."),
+}
+
 lfs_archive = repository_rule(
     doc = "Export the contents from an on-demand LFS archive. The corresponding path should be added to be ignored " +
           "in `.lfsconfig`.",
-    implementation = _download_and_extract_lfs,
+    implementation = _download_and_extract_lfs_archive,
     attrs = {
         "src": attr.label(mandatory = True, doc = "Local path to the LFS archive to extract."),
-        "build_file_content": attr.string(doc = "The content for the BUILD file for this repository. " +
-                                                "Either build_file or build_file_content can be specified, but not both."),
-        "build_file": attr.label(doc = "The file to use as the BUILD file for this repository. " +
-                                       "Either build_file or build_file_content can be specified, but not both."),
-        "strip_prefix": attr.string(default = "", doc = "A directory prefix to strip from the extracted files. "),
-    },
+    } | _lfs_archive_attrs,
+)
+
+lfs_archives = repository_rule(
+    doc = "Overlay the contents from on-demand LFS archives. The corresponding paths should be added to be ignored " +
+          "in `.lfsconfig`.",
+    implementation = _download_and_extract_lfs_archives,
+    attrs = {
+        "srcs": attr.label_list(doc = "Local paths to the LFS archives to extract in order.", mandatory = True),
+    } | _lfs_archive_attrs,
 )
 
 lfs_files = repository_rule(