如何分析 shell command 的输出？

Emacs-general
1

我想通过分析 git diff的结果，生成一些内容放到 magit 的commit-msg里面，现在第一步就没想明白， 如果把shell-command的结果放到一个buffer里，我能想到的是用switch-to-buffer来切换，处理完结果后再切换原来的状态，这样UI界面应该会闪烁吧，体验肯定不好，如果用shell-command-to-string的话，处理字符串好像比较麻烦，求赐教

2 
with-current-buffer is a macro defined in subr.el.gz.

Signature
(with-current-buffer BUFFER-OR-NAME &rest BODY)

Documentation
Execute the forms in BODY with BUFFER-OR-NAME temporarily current.

BUFFER-OR-NAME must be a buffer or the name of an existing buffer.
The value returned is the value of the last form in BODY.  See
also with-temp-buffer.

其实可以用process-lines

(let ((default-directory "/home/chino/.emacs.d/lib/site-lisp/ace-window"))
  (process-lines "git" "diff"))
;; =>
;; ("diff --git a/ace-window.el b/ace-window.el"
;;  "index 3a19324..306dd26 100644"
;;  "--- a/ace-window.el"
;;  "+++ b/ace-window.el"
;;  "@@ -1,3 +1,4 @@"
;;  "+FOOBAR"
;;  " ;;; ace-window.el --- Quickly switch windows. -*- lexical-binding: t -*-"
;;  " "
;;  " ;; Copyright (C) 2015  Free Software Foundation, Inc.")
3

哇，神速啊，谢谢，我尝试下再来汇报

4

目前可以提取出内容了，但还没有找到方法自动插入到 COMMIT_EDITMSG

(defun my-insert-change-log ()
" Inter change log from the result of `my-parse-git-diff'
"
  (interactive)
  (let* ((changes (my-parse-git-diff)))
    (dolist (file-changes changes)
      (insert (car file-changes))
      (insert "\n")
      (dolist (change (cadr file-changes))
        (insert (format "    %s\n" change))))))

(defun my-parse-git-diff ()
  "Parse change log from output of \"git diff\"
the change log should be style with :
 // 2020-12-14 comment string
or
 // 2020-12-14 12:12:12 comment string

Return alist with structure: '( (fn1 (log-str log-str)) (fn2 (log-str log-str)) )
"
  (let* ((fn nil)
         (log-strings)
         (file-result);; '(fn (log-str1 ...))
         (alist (process-lines  "git" "--no-pager" "diff" "--no-color" "-U0" "--cached")))
    (dolist (line alist)
      (and (string-prefix-p "diff --git a/" line)
           (or (and fn
                    (add-to-list 'file-result (list fn log-strings)))
               t)
           ;; save filename
           (setq fn (substring (nth 2 (split-string line)) 2))
           (setq log-strings '()))
      (and (string-match (concat "\\(//\\s-?+"
                                 (format-time-string "%Y-%m-%d");; date 2020-12-14
                                 "\\)"
                                 "\\(\\s-?+[0-9:]+\\)?";; time h:m:s
                                 "\\s-?\\(.*$\\)") line)
           (add-to-list 'log-strings (match-string 3 line))))
    (add-to-list 'file-result (list fn log-strings))))