repart: Add --split option to generate split artifacts

For use with sysupdate or other systemd tooling, it's useful to be
able to generate split artifacts from disk images, where each
partition is written to a separate file. Let's support this with
a --split switch for repart and a SplitName= configuration option.

--split enables split artifacts generation, and SplitName= configures
for which partition to generate split artifacts, and which suffix to
add to the split artifact name.

For SplitName=, we add support for some extra specifiers, more specifically
the partition Type UUID and the partition UUID.

1 files changed, 51 insertions, 2 deletions

diff --git a/man/repart.d.xml b/man/repart.d.xml
index df5338c92a..280ce6b8ea 100644
--- a/man/repart.d.xml
+++ b/man/repart.d.xml
@@ -669,6 +669,15 @@
         all partition types that support it, except if the partition is marked read-only (and thus
         effectively, defaults to off for Verity partitions).</para></listitem>
       </varlistentry>
+
+      <varlistentry>
+        <term><varname>SplitName=</varname></term>
+
+        <listitem><para>Configures the suffix to append to split artifacts when the <option>--split</option>
+        option of <command>systemd-repart</command> is used. Simple specifier expansion is supported, see
+        below. Defaults to <literal>%t</literal>. To disable split artifact generation for a partition, set
+        <varname>SplitName=</varname> to <literal>-</literal>.</para></listitem>
+      </varlistentry>
     </variablelist>
   </refsect1>
 
@@ -676,8 +685,8 @@
     <title>Specifiers</title>
 
     <para>Specifiers may be used in the <varname>Label=</varname>, <varname>CopyBlocks=</varname>,
-    <varname>CopyFiles=</varname>, <varname>MakeDirectories=</varname> settings. The following expansions are
-    understood:</para>
+    <varname>CopyFiles=</varname>, <varname>MakeDirectories=</varname>, <varname>SplitName=</varname>
+    settings. The following expansions are understood:</para>
       <table class='specifiers'>
         <title>Specifiers available</title>
         <tgroup cols='3' align='left' colsep='1' rowsep='1'>
@@ -710,6 +719,46 @@
           </tbody>
         </tgroup>
       </table>
+
+    <para>Additionally, for the <varname>SplitName=</varname> setting, the following specifiers are also
+    understood:</para>
+      <table class='specifiers'>
+        <title>Specifiers available</title>
+        <tgroup cols='3' align='left' colsep='1' rowsep='1'>
+          <colspec colname="spec" />
+          <colspec colname="mean" />
+          <colspec colname="detail" />
+          <thead>
+            <row>
+              <entry>Specifier</entry>
+              <entry>Meaning</entry>
+              <entry>Details</entry>
+            </row>
+          </thead>
+          <tbody>
+            <row id='T'>
+              <entry><literal>%T</literal></entry>
+              <entry>Partition Type UUID</entry>
+              <entry>The partition type UUID, as configured with <varname>Type=</varname></entry>
+            </row>
+            <row id='t'>
+              <entry><literal>%t</literal></entry>
+              <entry>Partition Type Identifier</entry>
+              <entry>The partition type identifier corresponding to the partition type UUID</entry>
+            </row>
+            <row id='U'>
+              <entry><literal>%U</literal></entry>
+              <entry>Partition UUID</entry>
+              <entry>The partition UUID, as configured with <varname>UUID=</varname></entry>
+            </row>
+            <row id='n'>
+              <entry><literal>%n</literal></entry>
+              <entry>Partition Number</entry>
+              <entry>The partition number assigned to the partition</entry>
+            </row>
+          </tbody>
+        </tgroup>
+      </table>
   </refsect1>
 
   <refsect1>