treefile: Support inline postprocess element (for inheritance)

I'm trying to have a more opinionated model where custom builds
use inheritance, and currently one can only have a single
`postprocess-script`.

Further, in YAML it's very convenient to use inline vs external
data.

Closes: #1527
Approved by: jlebon

docs/manual/treefile.md

@@ -173,6 +173,16 @@ It supports the following parameters:
 
    Note this does not alter the RPM database, so `rpm -V` will complain.
 
+   If you want to depend on network access, or tools not in the target host,
+   you can use the split-up `rpm-ostree compose install`
+   and `rpm-ostree compose postprocess/commit` commands.
+
+ * `postprocess`: array of string, optional: This is an *inline* script
+   variant of `postprocess-script` that is also an array, so it works
+   correctly with inheritance.  If both `postprocess-script` and `postprocess`
+   are provided, then `postprocess-script` will be executed after all
+   other `postprocess`.
+
  * `include`: string, optional: Path to another treefile which will be
    used as an inheritance base.  The semantics for inheritance are:
    Non-array values in child values override parent values.  Array

rust/src/treefile.rs

@@ -318,8 +318,12 @@ pub struct TreeComposeConfig {
     // Content manipulation
     #[serde(skip_serializing_if = "Option::is_none")]
     #[serde(rename = "postprocess-script")]
+    // This one references an external filename
     pub postprocess_script: Option<String>,
     #[serde(skip_serializing_if = "Option::is_none")]
+    // This one is inline, and supports multiple (hence is useful for inheritance)
+    pub postprocess: Option<Vec<String>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     #[serde(rename = "add-files")]
     pub add_files: Option<Vec<String>>,
     #[serde(skip_serializing_if = "Option::is_none")]

src/libpriv/rpmostree-postprocess.c

@@ -1721,11 +1721,40 @@ rpmostree_treefile_postprocessing (int            rootfs_fd,
   if (!copy_additional_files (rootfs_fd, context_directory, treefile, cancellable, error))
     return FALSE;
 
+  if (json_object_has_member (treefile, "postprocess"))
+    {
+      JsonArray *postprocess_inlines = json_object_get_array_member (treefile, "postprocess");
+      guint len = json_array_get_length (postprocess_inlines);
+
+      for (guint i = 0; i < len; i++)
+        {
+          const char *script = _rpmostree_jsonutil_array_require_string_element (postprocess_inlines, i, error);
+          if (!script)
+            return FALSE;
+
+          g_autofree char* binpath = g_strdup_printf ("/usr/bin/rpmostree-postprocess-inline-%u", i);
+          const char *target_binpath = binpath + 1;
+
+          if (!glnx_file_replace_contents_with_perms_at (rootfs_fd, target_binpath,
+                                                         (guint8*)script, -1,
+                                                         0755, (uid_t)-1, (gid_t)-1,
+                                                         GLNX_FILE_REPLACE_NODATASYNC,
+                                                         cancellable, error))
+            return FALSE;
+          g_print ("Executing `postprocess` inline script '%u'\n", i);
+          char *child_argv[] = { binpath, NULL };
+          if (!run_bwrap_mutably (rootfs_fd, binpath, child_argv, unified_core_mode, cancellable, error))
+            return glnx_prefix_error (error, "While executing inline postprocessing script '%i'", i);
+
+          if (!glnx_unlinkat (rootfs_fd, target_binpath, 0, error))
+            return FALSE;
+        }
+    }
+
   const char *postprocess_script = NULL;
   if (!_rpmostree_jsonutil_object_get_optional_string_member (treefile, "postprocess-script",
                                                               &postprocess_script, error))
     return FALSE;
-
   if (postprocess_script)
     {
       const char *bn = glnx_basename (postprocess_script);

tests/compose-tests/test-misc-tweaks.sh

@@ -21,9 +21,16 @@ pysetjsonmember "add-files" '[["foo.txt", "/usr/etc/foo.txt"],
                               ["baz.txt", "/usr/share/baz.txt"],
                               ["bar.txt", "/etc/bar.txt"]]'
 pysetjsonmember "postprocess-script" \"$PWD/postprocess.sh\"
+pysetjsonmember "postprocess" '["""#!/bin/bash
+touch /usr/share/postprocess-testing""",
+"""#!/bin/bash
+rm /usr/share/postprocess-testing
+touch /usr/share/postprocess-testing-done"""]'
 cat > postprocess.sh << EOF
 #!/bin/bash
 set -xeuo pipefail
+# Ordering should be after postprocess
+rm /usr/share/postprocess-testing-done
 echo misc-tweaks-postprocess-done > /usr/share/misc-tweaks-postprocess-done.txt
 cp -a /usr/etc/foo.txt /usr/share/misc-tweaks-foo.txt
 EOF