[master] bffb15e First stab at hit-for-pass documentation

[Dridi Boukelmoune]

commit bffb15e9f58c4e4056c39093f19d1286a5df6066
Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
Date:   Wed Mar 1 10:14:54 2017 +0100

    First stab at hit-for-pass documentation
    
    I wanted to update cache_fetch.dot to add the new transition from v_b_r
    but I wasn't sure how the 304 case would be handled. The documentation
    for built-in subs and the diagrams are also missing the fail transition.
    The latter may deserve a special treatment.

diff --git a/doc/sphinx/users-guide/vcl-built-in-subs.rst b/doc/sphinx/users-guide/vcl-built-in-subs.rst
index 0128233..a3106cd 100644
--- a/doc/sphinx/users-guide/vcl-built-in-subs.rst
+++ b/doc/sphinx/users-guide/vcl-built-in-subs.rst
@@ -335,6 +335,11 @@ The `vcl_backend_response` subroutine may terminate with calling
     delivery to any waiting client requests, possibly in parallel
     (streaming).
 
+  ``pass(duration)``
+    Mark the object as a hit-for-pass for the given duration. Subsequent
+    lookups hitting this object will be turned into passed transactions,
+    as if ``vcl_recv`` had returned ``pass``.
+
   ``abandon``
     Abandon the backend request. Unless the backend request was a
     background fetch, control is passed to :ref:`vcl_synth` on the
diff --git a/include/tbl/vsl_tags.h b/include/tbl/vsl_tags.h
index 93a2bfe..2231b17 100644
--- a/include/tbl/vsl_tags.h
+++ b/include/tbl/vsl_tags.h
@@ -219,7 +219,7 @@ SLTM(TTL, 0, "TTL set on object",
 	"\t|  |  |  +------------------ Keep\n"
 	"\t|  |  +--------------------- Grace\n"
 	"\t|  +------------------------ TTL\n"
-	"\t+--------------------------- \"RFC\" or \"VCL\"\n"
+	"\t+--------------------------- \"RFC\", \"VCL\" or \"HFP\"\n"
 	"\n"
 	"The last four fields are only present in \"RFC\" headers.\n\n"
 	"Examples::\n\n"