Improve LaTeX option parsing...

in cases where we run into trouble parsing inlines til the
closing `]`, e.g. quotes, we return a plain string with the
option contents. Previously we mistakenly included the brackets
in this string.

Closes #6869.

src/Text/Pandoc/Readers/LaTeX.hs

@@ -559,7 +559,9 @@ tok = try $ spaces >> grouped inline <|> inlineCommand' <|> singleChar'
           return $ str t
 
 opt :: PandocMonad m => LP m Inlines
-opt = bracketed inline <|> (str <$> rawopt)
+opt = bracketed inline
+      <|>
+      (str . T.dropWhile (=='[') . T.dropWhileEnd (==']') <$> rawopt)
 
 paropt :: PandocMonad m => LP m Inlines
 paropt = parenWrapped inline

test/command/6869.md

@@ -0,0 +1,6 @@
+```
+% pandoc -f latex -t native
+\cite[„Aber“]{key}
+^D
+[Para [Cite [Citation {citationId = "key", citationPrefix = [], citationSuffix = [Str "\8222Aber\8220"], citationMode = NormalCitation, citationNoteNum = 0, citationHash = 0}] [RawInline (Format "latex") "\\cite[\8222Aber\8220]{key}"]]]
+```