Replace save-excursion, set-buffer with with-current-buffer

When byte-compiling magit.el, Emacs throws several warnings saying
`save-excursion' defeated by `set-buffer'. Eliminate these warnings by
replacing calls to save-excursion followed by set-buffer with
with-current-buffer.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>

magit.el

@@ -1257,8 +1257,7 @@ FUNC should leave point at the end of the modified region"
     (magit-set-mode-line-process
      (magit-process-indicator-from-command cmd-and-args))
     (setq magit-process-client-buffer (current-buffer))
-    (save-excursion
-      (set-buffer buf)
+    (with-current-buffer buf
       (view-mode 1)
       (set (make-local-variable 'view-no-disable-on-exit) t)
       (setq view-exit-action
@@ -1719,8 +1718,7 @@ Please see the manual for a complete description of Magit.
 (defun magit-find-buffer (submode &optional dir)
   (let ((topdir (magit-get-top-dir (or dir default-directory))))
     (dolist (buf (buffer-list))
-      (if (save-excursion
-	    (set-buffer buf)
+      (if (with-current-buffer buf
 	    (and default-directory
 		 (equal (expand-file-name default-directory) topdir)
 		 (eq major-mode 'magit-mode)
@@ -1732,8 +1730,7 @@ Please see the manual for a complete description of Magit.
 
 (defun magit-for-all-buffers (func &optional dir)
   (dolist (buf (buffer-list))
-    (save-excursion
-      (set-buffer buf)
+    (with-current-buffer buf
       (if (and (eq major-mode 'magit-mode)
 	       (or (null dir)
 		   (equal default-directory dir)))
@@ -3027,8 +3024,7 @@ Prefix arg means justify as well."
 	(replace-match "\n" nil nil))))
 
 (defun magit-log-edit-append (str)
-  (save-excursion
-    (set-buffer (get-buffer-create magit-log-edit-buffer-name))
+  (with-current-buffer (get-buffer-create magit-log-edit-buffer-name)
     (goto-char (point-max))
     (insert str "\n")))
 
@@ -3038,8 +3034,7 @@ Prefix arg means justify as well."
   (let ((buf (get-buffer magit-log-edit-buffer-name))
 	(result nil))
     (if buf
-	(save-excursion
-	  (set-buffer buf)
+	(with-current-buffer buf
 	  (goto-char (point-min))
 	  (while (looking-at "^\\([A-Za-z0-9-_]+\\): *\\(.*\\)$")
 	    (setq result (acons (intern (downcase (match-string 1)))
@@ -3052,8 +3047,7 @@ Prefix arg means justify as well."
 
 (defun magit-log-edit-set-fields (fields)
   (let ((buf (get-buffer-create magit-log-edit-buffer-name)))
-    (save-excursion
-      (set-buffer buf)
+    (with-current-buffer buf
       (goto-char (point-min))
       (if (search-forward-regexp (format "^\\([A-Za-z0-9-_]+:.*\n\\)+%s"
 					 (regexp-quote magit-log-header-end))
@@ -3637,8 +3631,7 @@ With a non numeric prefix ARG, show all entries"
 	     (args (magit-rev-range-to-git range))
 	     (buf (get-buffer-create "*magit-diff*")))
 	(display-buffer buf)
-	(save-excursion
-	  (set-buffer buf)
+	(with-current-buffer buf
 	  (magit-mode-init dir 'diff #'magit-refresh-diff-buffer range args)
 	  (magit-diff-mode t)))))
 
@@ -4120,8 +4113,7 @@ With prefix force the removal even it it hasn't been merged."
 (defun magit-list-buffers ()
   "Returns a list of magit buffers."
   (delq nil (mapcar (lambda (b)
-                      (save-excursion
-                        (set-buffer b)
+                      (with-current-buffer b
                         (when (eq major-mode 'magit-mode)
                           b)))
                     (buffer-list))))
@@ -4140,8 +4132,7 @@ With prefix force the removal even it it hasn't been merged."
   (remove-dupes
    (sort
     (mapcar (lambda (b)
-              (save-excursion
-                (set-buffer b)
+              (with-current-buffer b
                 (directory-file-name default-directory)))
             (magit-list-buffers))
     'string=)))