added description of ccache feature in hammer in user guide

diff --git a/doc/guide/hammer.xml b/doc/guide/hammer.xml
index 610471e4a2864e36409b8e75598293f3854ed1d5..9d9f1fbccd0c8953344df0e62c001e1a57aa5ec3 100644 (file)
--- a/doc/guide/hammer.xml
+++ b/doc/guide/hammer.xml
@@ -112,6 +112,19 @@ freebsd:
     <screen><userinput>./hammer.py ssh -p virtualbox -s freebsd -r 12.0</userinput></screen>
   </para>
 
+  <para>
+    It is possible to speed up subsequent Hammer builds. To achieve this Hammer
+    employs <ulink url="https://ccache.samba.org/">CCache</ulink>. During compilation
+    CCache stores object to shared folder. In subsequent runs instead doing actuall
+    compilation CCache just returns stored earlier objects. Cache with objects for
+    reuse needs to be stored outside of VM or LXC. To indicate such folder Hammer
+    requires providing --ccache-dir parameter. In indicated folder there are stored
+    objects for each target operating system separatelly.
+    <screen><userinput>
+      ./hammer.py build -p lxc -s ubuntu -r 18.04 --ccache-dir ~/kea-ccache
+    </userinput></screen>
+  </para>
+
   <para>
     For more information check: <screen><userinput>./hammer.py --help</userinput></screen>
   </para>