Feature request: command-line options for jq adapter

[titaniumtraveler]

Motivation

When writing jq queries it is sometimes necessary to configure some command-line
options for that connection. (In my case specifically --slurp)

Possible Solution

A possible solution would be to allow using the query parameter of the
connection for configuring these.

As an example how that could be done I patched the jq adapter to at least
support ?slurp=true to enable --slurp.
(It is not especially good code and the final interface to set those options
should probably be something better than just ?slurp=true, but it was what
enough to get done what I needed in the moment)

diff --git a/autoload/db/adapter/jq.vim b/autoload/db/adapter/jq.vim
index ffee3df..25c3904 100644
--- a/autoload/db/adapter/jq.vim
+++ b/autoload/db/adapter/jq.vim
@@ -11,16 +11,24 @@ function! db#adapter#jq#output_extension(...) abort
 endfunction
 
 function! s:path_args(url) abort
-  let input = db#url#file_path(a:url)
-  if input =~# '^[\/]\=$'
-    return ['--null-input']
+  let url = db#url#parse(a:url)
+
+  let args = []
+  if get(url.params, "slurp") ==? "true"
+    let args += ["--slurp"]
+  endif
+
+  if empty(url.opaque)
+    return args + ['--null-input']
   else
-    return ['--', input]
+    let args += ['--', url.opaque]
+    return args
   endif
 endfunction
 
 function! db#adapter#jq#input(url, in) abort
-  return ['jq', '--from-file', a:in] + s:path_args(a:url)
+  let args = ['jq', '--from-file', a:in] + s:path_args(a:url)
+  return args
 endfunction
 
 function! db#adapter#jq#auth_input() abort

The patch is on top of the current master. (9f0ca8b)