Improve block parameter parsing

The actual parameter parsing logic in emacs org mode is quite complex [1]. All
we want for now is to handle parameter values containing spaces [2]. Splitting
on ` :` gets us close enough for now. As I'm very opposed to copying 100 lines
of parameter parsing logic just to get exports right let's wait for use cases -
no hurt in gathering requirements as we go.

[1] https://github.com/bzg/org-mode/blob/master/lisp/ob-core.el#L1481
[2] I never ran into such parameters before and wrongly assumed that splitting
on spaces would be enough. boy was i wrong - just look at that massive
function [1]! that's why we can't have nice things!

org/block.go

@@ -54,7 +54,7 @@ func isRawTextBlock(name string) bool { return name == "SRC" || name == "EXAMPLE
 
 func (d *Document) parseBlock(i int, parentStop stopFn) (int, Node) {
 	t, start := d.tokens[i], i
-	name, parameters := t.content, strings.Fields(t.matches[3])
+	name, parameters := t.content, splitParameters(t.matches[3])
 	trim := trimIndentUpTo(d.tokens[i].lvl)
 	stop := func(d *Document, i int) bool {
 		return i >= len(d.tokens) || (d.tokens[i].kind == "endBlock" && d.tokens[i].content == name)
@@ -121,6 +121,19 @@ func trimIndentUpTo(max int) func(string) string {
 	}
 }
 
+func splitParameters(s string) []string {
+	parameters, parts := []string{}, strings.Split(s, " :")
+	lang, rest := strings.TrimSpace(parts[0]), parts[1:]
+	if lang != "" {
+		parameters = append(parameters, lang)
+	}
+	for _, p := range rest {
+		kv := strings.SplitN(p+" ", " ", 2)
+		parameters = append(parameters, ":"+kv[0], strings.TrimSpace(kv[1]))
+	}
+	return parameters
+}
+
 func (b Block) ParameterMap() map[string]string {
 	if len(b.Parameters) == 0 {
 		return nil

org/testdata/blocks.html

@@ -40,6 +40,9 @@ a source block with results
 a source block that only exports results
 </pre>
 <pre class="example">
+but the result block is
+</pre>
+<pre class="example">
 an example block with
 multiple lines including
 

org/testdata/blocks.org

@@ -38,6 +38,14 @@ echo a source block that only exports results
 #+RESULTS:
 : a source block that only exports results
 
+#+begin_src bash :cmdline -foo -bar :exports results
+# the code block is not rendered
+echo but the result block is
+#+end_src
+
+#+RESULTS:
+: but the result block is
+
 #+BEGIN_EXAMPLE foo bar baz
 an example block with
 multiple lines including

org/testdata/blocks.pretty_org

@@ -38,6 +38,14 @@ echo a source block that only exports results
 #+RESULTS:
 : a source block that only exports results
 
+#+BEGIN_SRC bash :cmdline -foo -bar :exports results
+# the code block is not rendered
+echo but the result block is
+#+END_SRC
+
+#+RESULTS:
+: but the result block is
+
 #+BEGIN_EXAMPLE foo bar baz
 an example block with
 multiple lines including