portable: add flag to return extension-releases in GetImageMetadataWithExtensions

Return the name of each extension and the associated extension-release
file, and pretty-print them in 'portablectl inspect', if a new flag
is passed.

$ portablectl inspect --extension app2 --extension app0  minimal app0 app1
(Matching unit files with prefixes 'app0', 'app1'.)
Image:
        /run/portables/minimal.raw
Portable Service:
        n/a
Operating System:
        Debian GNU/Linux 10 (buster)
Extension:
        /run/portables/app2.raw
        Extension Scope:
                n/a
        Extension Compatibility Level:
                n/a
        Portable Service:
                n/a
        Portable Prefixes:
                n/a
        Operating System:
                n/a (debian 10)
Extension:
        /run/portables/app0.raw
        Extension Scope:
                n/a
        Extension Compatibility Level:
                n/a
        Portable Service:
                n/a
        Portable Prefixes:
                n/a
        Operating System:
                n/a (debian 10)
Unit files:
        app0.service

1 files changed, 9 insertions, 1 deletions

diff --git a/man/org.freedesktop.portable1.xml b/man/org.freedesktop.portable1.xml
index a63b6aeebe..4842885c0c 100644
--- a/man/org.freedesktop.portable1.xml
+++ b/man/org.freedesktop.portable1.xml
@@ -193,7 +193,15 @@ node /org/freedesktop/portable1 {
       This method is a superset of <function>GetImageMetadata()</function> with the addition of
       a list of extensions as input parameter, which were overlaid on top of the main
       image via <function>AttachImageWithExtensions()</function>.
-      The <varname>flag</varname> parameter is currently unused and reserved for future purposes.</para>
+      The <varname>flag</varname> parameter can be used to request that, before the units, the path of
+      each extension and an array of bytes with the content of the respective extension-release file
+      are sent. One such structure will be sent for each extension named in the input arguments. The
+      flag value to enable this functionality is defined as follows:</para>
+
+      <programlisting>
+#define PORTABLE_INSPECT_EXTENSION_RELEASES  (UINT64_C(1) &lt;&lt; 1)
+      </programlisting>
+
 
       <para><function>GetImageState()</function> retrieves the image state as one of the following
       strings: