minirst: find admonitions before pruning comments and adding margins

Lines with only a directive are not deleted anymore because they are detected
before comments are deleted by prunecomments().
addmargins() will be adapted later.

mercurial/minirst.py

@@ -633,9 +633,9 b' def parse(text, indent=0, keep=None):'
     blocks = splitparagraphs(blocks)
     blocks = updatefieldlists(blocks)
     blocks = updateoptionlists(blocks)
+    blocks = findadmonitions(blocks)
     blocks = addmargins(blocks)
     blocks = prunecomments(blocks)
-    blocks = findadmonitions(blocks)
     return blocks, pruned
 
 def formatblocks(blocks, width):