man: add note regarding editing user groups

Currently the manual doesn't clearly say whether `homectl update username -G group` will append the group to the user, or overwrite the list and remove user from the groups that aren't specified.

Fix this by updating the manual, basing the change on the usermod manual.

diff --git a/man/homectl.xml b/man/homectl.xml
index 14877a0cde047e24265139e170443e624e671c8a..3a4c6e5f5b1de0bd6ac8df5b0603e03ddebfcfea 100644 (file)
--- a/man/homectl.xml
+++ b/man/homectl.xml
@@ -268,7 +268,8 @@
         independently, for example with <citerefentry
         project='man-pages'><refentrytitle>groupadd</refentrytitle><manvolnum>8</manvolnum></citerefentry>. If
         non-existent groups that are listed there are ignored. This option may be used more than once, in
-        which case all specified group lists are combined.</para></listitem>
+        which case all specified group lists are combined. If the user is currently a member of a group
+        which is not listed, the user will be removed from the group.</para></listitem>
       </varlistentry>
 
       <varlistentry>