[O] [Discuss] make :tangle header argument respect :dir could save info typing

[stardiviner]

I realized one thing, the combination of ~:mkdir~, ~:dir~, and ~:tangle~ does 
not work
good enough. Can make ~:tangle~ respect ~:dir~ too. WDYT?

Here is an example:

#+begin_src clojure :mkdirp yes :dir "data/code/clj-crawler-demo" :tangle 
"src/clj_crawler_demo/core.clj"
(ns clj-crawler-demo.core
  (:require [clj-http.client :as http])
  (:require [net.cgrand.enlive-html :as html]))

(html/select
 (-> (http/get "https://www.baidu.com";)
     :body
     html/html-snippet)
 [:div])
#+end_src

Why need this? If ~:tangle~ respect ~:dir~, it will don't need the complete 
path to
tangled file. And when the source block has other header argument need dir like
~:file~, this will make ~:tangle~ and other related header arguments shorter.

If ~:tangle~ does not respect ~:dir~, user need to repeat the path:

#+begin_src clojure :mkdirp yes :dir "data/code/clj-crawler-demo" :tangle 
"data/code/clj-crawler-demo/src/clj_crawler_demo/core.clj"
(ns clj-crawler-demo.core
  (:require [clj-http.client :as http])
  (:require [net.cgrand.enlive-html :as html]))

(html/select
 (-> (http/get "https://www.baidu.com";)
     :body
     html/html-snippet)
 [:div])
#+end_src

This is long, I know there is ~#+headers:~ for source block. But reduce info 
would
be better. I also consider the disadvantage of this change. Some user's existing
source block might be broken.

Let's level this change for discussion.

-- 
[ stardiviner ]
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