Add MotherDuck adapter

README.markdown

@@ -14,6 +14,7 @@ take on [dbext.vim][], improving on it on the following ways:
   - Impala
   - jq
   - MongoDB
+  - MotherDuck
   - MySQL
   - MariaDB
   - Oracle

autoload/db/adapter/duckdb.vim

@@ -33,7 +33,7 @@ function! db#adapter#duckdb#command(url) abort
 endfunction
 
 function! db#adapter#duckdb#interactive(url) abort
-  return db#adapter#duckdb#command(a:url) + ['-column', '-header']
+  return db#adapter#duckdb#command(a:url) + ['-cmd', '.output']
 endfunction
 
 function! db#adapter#duckdb#tables(url) abort

autoload/db/adapter/md.vim

@@ -0,0 +1,34 @@
+function! db#adapter#md#canonicalize(url) abort
+  return a:url
+endfunction
+
+function! s:dbname(url) abort
+  let parsed = db#url#parse(a:url)
+  if has_key(parsed, 'opaque')
+    return parsed.opaque
+  endif
+  return ''
+endfunction
+
+function! db#adapter#md#dbext(url) abort
+  return {'dbname': s:dbname(a:url)}
+endfunction
+
+function! db#adapter#md#command(url) abort
+  if a:url != ''
+    return ['duckdb', a:url]
+  endif
+  return ['duckdb', 'md:']
+endfunction
+
+function! db#adapter#md#interactive(url) abort
+  return db#adapter#md#command(a:url) + ['-cmd', '.output']
+endfunction
+
+function! db#adapter#md#tables(url) abort
+  return split(join(db#systemlist(db#adapter#md#command(a:url) + ['-noheader', '-c', '.tables'])))
+endfunction
+
+function! db#adapter#md#massage(input) abort
+  return a:input . "\n;"
+endfunction

doc/dadbod.txt

@@ -143,6 +143,20 @@ MongoDB ~
 <
 Any valid MongoDB connection string URI can be used.
 
+                                                *dadbod-md*
+MotherDuck ~
+>
+    md:
+    md:[<database>]
+<
+MotherDuck authenticates using a token stored as an environment variable
+`motherduck_token`. If this environment variable is missing, all invocations
+will open a browser and prompt the user to login to the MotherDuck console.
+
+If the database is provided, it will be used as the default database (so
+queries do not have to specify a database. If not, queries must specify a
+database.
+
                                                 *dadbod-mysql*
 MySQL ~
 >