Flatten AST form for pipelines

* geesh/parser.scm (make-parser): Splice in commands to keep
'<sh-pipeline>' flat.
* tests/parser.scm: Adjust and add tests accordingly.

geesh/parser.scm

@@ -281,15 +281,19 @@ the same number of times.)"
 
    (pipeline
     (pipe-sequence)
-    : (if (null? (cdr $1)) (car $1) $1)
+    : (if (null? (cdr $1))
+          (car $1)
+          `(<sh-pipeline> ,@(reverse! $1)))
     (Bang pipe-sequence)
-    : `(<sh-not> ,$2))
+    : `(<sh-not> ,(if (null? (cdr $2))
+                      (car $2)
+                      `(<sh-pipeline> ,@(reverse! $2)))))
 
    (pipe-sequence
     (command)
     : `(,$1)
     (pipe-sequence PIPE linebreak command)
-    : `(<sh-pipeline> ,(append $1 (list $4))))
+    : (cons $4 $1))
 
    (command
     (simple-command)

tests/parser.scm

@@ -123,11 +123,20 @@
              (<sh-exec> "echo" "baz"))
   (parse "echo foo || echo bar && echo baz"))
 
+(test-equal "Parses negations"
+  '(<sh-not> (<sh-exec> "echo" "foo"))
+  (parse "! echo foo"))
+
+(test-equal "Parses negated pipelines"
+  '(<sh-not> (<sh-pipeline> (<sh-exec> "echo" "foo")
+                            (<sh-exec> "echo" "bar")))
+  (parse "! echo foo | echo bar"))
+
 ;; Pipelines
 
 (test-equal "Parses pipelines"
-  '(<sh-pipeline> ((<sh-exec> "cat" "foo.txt")
-                   (<sh-exec> "grep" "bar")))
+  '(<sh-pipeline> (<sh-exec> "cat" "foo.txt")
+                  (<sh-exec> "grep" "bar"))
   (parse "cat foo.txt | grep bar"))
 
 ;; Brace groups and subshells