add lxcconfig

rules.bzl

@@ -1,15 +1,28 @@
+_undocker_cli = attr.label(
+    doc = "undocker cli; private and may not be overridden",
+    cfg = "host",
+    default = Label("//src/undocker:undocker"),
+    allow_single_file = True,
+    executable = True,
+)
+_input_container = attr.label(
+    doc = "Input container tarball",
+    mandatory = True,
+    allow_single_file = [".tar"],
+)
+
 def _rootfs_impl(ctx):
-    outf = ctx.attr.name + ".tar"
-    out = ctx.actions.declare_file(outf)
+    out = ctx.actions.declare_file(ctx.attr.name + ".tar")
     ctx.actions.run(
         outputs = [out],
         inputs = ctx.files.src,
         executable = ctx.files._undocker[0],
         arguments = [
             "rootfs",
-            ctx.files.src.to_list()[0].path,
-            outf,
+            ctx.files.src[0].path,
+            out.path,
         ],
+        mnemonic = "RootFS",
     )
     return [DefaultInfo(
         files = depset([out]),
@@ -20,17 +33,34 @@ rootfs = rule(
     doc = "Generate a rootfs from a docker container image",
     implementation = _rootfs_impl,
     attrs = {
-        "src": attr.label(
-            doc = "Input container tarball",
-            mandatory = True,
-            allow_single_file = [".tar"],
-        ),
-        "_undocker": attr.label(
-            doc = "undocker cli; private and may not be overridden",
-            cfg = "host",
-            default = Label("//src/undocker:undocker"),
-            allow_single_file = True,
-            executable = True,
-        ),
+        "src": _input_container,
+        "_undocker": _undocker,
+    },
+)
+
+def _lxcconfig_impl(ctx):
+    out = ctx.actions.declare_file(ctx.attr.name + ".conf")
+    ctx.actions.run(
+        outputs = [out],
+        inputs = ctx.files.src,
+        executable = ctx.files._undocker[0],
+        arguments = [
+            "lxcconfig",
+            ctx.files.src[0].path,
+            out.path,
+        ],
+        mnemonic = "LXCConfig",
+    )
+    return [DefaultInfo(
+        files = depset([out]),
+        runfiles = ctx.runfiles(files = ctx.files.src),
+    )]
+
+lxcconfig = rule(
+    doc = "Generate lxc config from a docker container image",
+    implementation = _lxcconfig_impl,
+    attrs = {
+        "src": _input_container,
+        "_undocker": _undocker,
     },
 )