Add support for partials and path segments for Handlebars.

This introduces support for some missing features to the Handlebars lexer:
Partials and path segments. Partials mostly appeared to work before, but the
`>` in `{{> ... }}` would appear as a syntax error, as could other
components of the partial. This change introduces support for:

* Standard partials: `{{> partialName}}`
* Partials with parameters: `{{> partialName varname="value"}}`
* Ddynamic partials: `{{> (partialFunc)}}`
* Ddynamic partials with lookups: `{{> (lookup ../path "partialName")}}`
* Partial blocks: `{{> @partial-block}}`
* Inline partials: `{{#*inline}}..{{/inline}}`

It also introduces support for path segments, which can reference content in
the current context or in a parent context. For instance, `this.name`,
`this/name`, `./name`, `../name`, `this/name`, etc. These are all now tracked
as variables.

1 files changed, 68 insertions, 0 deletions

diff --git a/pygments/plugin.py b/pygments/plugin.py
new file mode 100644
index 00000000..b1f17449
--- /dev/null
+++ b/pygments/plugin.py
@@ -0,0 +1,68 @@
+# -*- coding: utf-8 -*-
+"""
+    pygments.plugin
+    ~~~~~~~~~~~~~~~
+
+    Pygments setuptools plugin interface. The methods defined
+    here also work if setuptools isn't installed but they just
+    return nothing.
+
+    lexer plugins::
+
+        [pygments.lexers]
+        yourlexer = yourmodule:YourLexer
+
+    formatter plugins::
+
+        [pygments.formatters]
+        yourformatter = yourformatter:YourFormatter
+        /.ext = yourformatter:YourFormatter
+
+    As you can see, you can define extensions for the formatter
+    with a leading slash.
+
+    syntax plugins::
+
+        [pygments.styles]
+        yourstyle = yourstyle:YourStyle
+
+    filter plugin::
+
+        [pygments.filter]
+        yourfilter = yourfilter:YourFilter
+
+
+    :copyright: Copyright 2006-2015 by the Pygments team, see AUTHORS.
+    :license: BSD, see LICENSE for details.
+"""
+LEXER_ENTRY_POINT = 'pygments.lexers'
+FORMATTER_ENTRY_POINT = 'pygments.formatters'
+STYLE_ENTRY_POINT = 'pygments.styles'
+FILTER_ENTRY_POINT = 'pygments.filters'
+
+def iter_entry_points(group_name):
+    try:
+        import pkg_resources
+    except ImportError:
+        return []
+
+    return pkg_resources.iter_entry_points(group_name)
+
+def find_plugin_lexers():
+    for entrypoint in iter_entry_points(LEXER_ENTRY_POINT):
+        yield entrypoint.load()
+
+
+def find_plugin_formatters():
+    for entrypoint in iter_entry_points(FORMATTER_ENTRY_POINT):
+        yield entrypoint.name, entrypoint.load()
+
+
+def find_plugin_styles():
+    for entrypoint in iter_entry_points(STYLE_ENTRY_POINT):
+        yield entrypoint.name, entrypoint.load()
+
+
+def find_plugin_filters():
+    for entrypoint in iter_entry_points(FILTER_ENTRY_POINT):
+        yield entrypoint.name, entrypoint.load()