Add support for using documentation siphons in multiple ways

Experiental support for generating  multiple output formats from the
same siphoned data.

Adds a contrived example to generate a plain list of all CLI commands
(the "itemlist" format).

Eventually we can consider moving the tempate procesisng into the
Output class as well as a way to override how the data is traversed
(ordered).

Change-Id: I77629a74a8fa0c7e583993469dc50491f72f13e7
Signed-off-by: Chris Luke <chrisy@flirble.org>

2 files changed, 153 insertions, 0 deletions

diff --git a/doxygen/siphon_templates/markdown/syscfg/index_header.md b/doxygen/siphon_templates/markdown/syscfg/index_header.md
new file mode 100644
index 00000000000..5d338a0472b
--- /dev/null
+++ b/doxygen/siphon_templates/markdown/syscfg/index_header.md
@@ -0,0 +1,111 @@
+{#
+# Copyright (c) 2016 Comcast Cable Communications Management, LLC.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#}
+# Startup Configuration    {{'{#'}}syscfg}
+
+The VPP network stack comes with several configuration options that can be
+provided either on the command line or in a configuration file.
+
+Specific applications built on the stack have been known to require a dozen
+arguments, depending on requirements. This section describes commonly-used
+options and parameters.
+
+You can find command-line argument parsers in the source code by searching for
+instances of the `VLIB_CONFIG_FUNCTION` macro. The invocation
+`VLIB_CONFIG_FUNCTION(foo_config, "foo")` will cause the function
+`foo_config` to receive all the options and values supplied in a parameter
+block named "`foo`", for example: `foo { arg1 arg2 arg3 ... }`.
+
+@todo Tell the nice people where this document lives so that the might
+help improve it!
+
+## Command-line arguments
+
+Parameters are grouped by a section name. When providing more than one
+parameter to a section all parameters for that section must be wrapped in
+curly braces.
+
+```
+/usr/bin/vpp unix { interactive cli-listen 127.0.0.1:5002 }
+```
+
+Which will produce output similar to this:
+
+    <startup diagnostic messages>
+        _______    _        _   _____  ___ 
+     __/ __/ _ \  (_)__    | | / / _ \/ _ \
+     _/ _// // / / / _ \   | |/ / ___/ ___/
+     /_/ /____(_)_/\___/   |___/_/  /_/    
+    
+    vpp# <start-typing>
+
+When providing only one such parameter the braces are optional. For example,
+the following command argument, `unix interactive` does not have braces:
+
+```
+/usr/bin/vpp unix interactive
+```
+
+The command line can be presented as a single string or as several; anything
+given on the command line is concatenated with spaces into a single string
+before parsing.
+
+VPP applications must be able to locate their own executable images. The
+simplest way to ensure this will work is to invoke a VPP application by giving
+its absolute path; for example: `/usr/bin/vpp <options>`. At startup, VPP
+applications parse through their own ELF-sections (primarily) to make lists
+of init, configuration, and exit handlers.
+
+When developing with VPP, in _gdb_ it's often sufficient to start an application
+like this at the `(gdb)` prompt:
+
+```
+run unix interactive
+```
+
+## Configuration file
+
+It is also possible to supply parameters in a startup configuration file the
+path of which is provided to the VPP application on its command line.
+
+The format of the configuration file is a simple text file with the same
+content as the command line but with the benefit of being able to use newlines
+to make the content easier to read. For example:
+
+```
+unix {
+  nodaemon
+  log /tmp/vpp.log
+  full-coredump
+  cli-listen localhost:5002
+}
+api-trace {
+  on
+}
+dpdk {
+  dev 0000:03:00.0
+}
+```
+
+VPP is then instructed to load this file with the `-c` option:
+
+```
+/usr/bin/vpp -c /etc/vpp/startup.conf
+```
+
+## Index of startup command sections
+
+[TOC]
+
diff --git a/doxygen/siphon_templates/markdown/syscfg/item_format.md b/doxygen/siphon_templates/markdown/syscfg/item_format.md
new file mode 100644
index 00000000000..53136115bbc
--- /dev/null
+++ b/doxygen/siphon_templates/markdown/syscfg/item_format.md
@@ -0,0 +1,42 @@
+{#
+# Copyright (c) 2016 Comcast Cable Communications Management, LLC.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#}
+{% set v = item['value'] %}
+{{ "@section %s %s" % (meta['label'], item['name']) }}
+{% if 'siphon_block' in item['meta'] %}
+{% set sb = item["meta"]["siphon_block"] %}
+{% if sb %}
+{# Extracted from the code in /*? ... ?*/ blocks #}
+
+### Description
+
+{{ sb }}
+{% endif %}
+{% endif %}
+{% if "name" in meta or "function" in item %}
+{# Gives some developer-useful linking #}
+
+### Declaration and implementation
+{% if "name" in meta %}
+
+{{ "Declaration: @ref %s (@ref %s line %d)" %
+   (meta['name'], meta["file"], item["meta"]["line_start"]) }}
+{% endif %}
+{% if "function" in item %}
+
+{{ "Implementation: @ref %s." % item["function"] }}
+{% endif %}
+{% endif %}
+