Delay inserting and washing of big diffs.

* magit.el (magit-set-section-needs-refresh-on-show): New.
(magit-section-set-hidden): Call magit-refresh when a
'needs-refresh-on-show' section is shown.
(magit-show-level): Wrap it in magit-with-refresh.
(magit-wash-diff, magit-wash-diff-section): Factored washing and
section construction into seperate functions.
(magit-insert-diff, magit-wash-numstat-diffs,
magit-wash-numstat-diff): New.  Use magit-insert-diff for visible
sections or for small changes.
(magit-insert-unstaged-changes): Use a numstat diff instead of a full diff.
(magit-insert-staged-changes): Likewise.

magit.el

@@ -463,7 +463,8 @@ Many Magit faces inherit from this one by default."
 ;; parent and grand-parent, etc provide the context.
 
 (defstruct magit-section
-  parent title beginning end children hidden type info)
+  parent title beginning end children hidden type info
+  needs-refresh-on-show)
 
 (defvar magit-top-section nil)
 (make-variable-buffer-local 'magit-top-section)
@@ -513,6 +514,11 @@ Many Magit faces inherit from this one by default."
 (defun magit-set-section-info (info &optional section)
   (setf (magit-section-info (or section magit-top-section)) info))
 
+(defun magit-set-section-needs-refresh-on-show (flag &optional section)
+  (setf (magit-section-needs-refresh-on-show
+	 (or section magit-top-section))
+	flag))
+
 (defmacro magit-create-buffer-sections (&rest body)
   (declare (indent 0))
   `(let ((inhibit-read-only t))
@@ -695,6 +701,9 @@ Many Magit faces inherit from this one by default."
 
 (defun magit-section-set-hidden (section hidden)
   (setf (magit-section-hidden section) hidden)
+  (if (and (not hidden)
+	   (magit-section-needs-refresh-on-show section))
+      (magit-refresh)
     (let ((inhibit-read-only t)
 	  (beg (save-excursion
 		 (goto-char (magit-section-beginning section))
@@ -704,7 +713,7 @@ Many Magit faces inherit from this one by default."
       (put-text-property beg end 'invisible hidden))
     (if (not hidden)
 	(dolist (c (magit-section-children section))
-	(magit-section-set-hidden c (magit-section-hidden c)))))
+	  (magit-section-set-hidden c (magit-section-hidden c))))))
 
 (defun magit-section-any-hidden (section)
   (or (magit-section-hidden section)
@@ -791,10 +800,11 @@ Many Magit faces inherit from this one by default."
 	(magit-section-show-level c (1+ level) threshold nil)))))
 
 (defun magit-show-level (level all)
+  (magit-with-refresh
     (if all
 	(magit-section-show-level magit-top-section 0 level nil)
       (let ((path (reverse (magit-section-lineage (magit-current-section)))))
-      (magit-section-show-level (car path) 0 level (cdr path)))))
+	(magit-section-show-level (car path) 0 level (cdr path))))))
 
 (defun magit-show-only-files ()
   (interactive)
@@ -1456,17 +1466,13 @@ Please see the manual for a complete description of Magit.
 
 (defvar magit-hide-diffs nil)
 
-(defun magit-wash-diff ()
+(defun magit-wash-diff-section ()
   (cond ((looking-at "^\\* Unmerged path \\(.*\\)")
-	 (let ((file (match-string-no-properties 1)))
-	   (magit-with-section file 'diff
 	 (delete-region (point) (line-end-position))
 	 (insert "\tUnmerged " file "\n")
-	     (magit-set-section-info (list 'unmerged file nil))))
+	 (magit-set-section-info (list 'unmerged file nil))
 	 t)
 	((looking-at "^diff")
-	 (let ((magit-section-hidden-default magit-hide-diffs))
-	   (magit-with-section (magit-current-line) 'diff
 	 (let ((file (magit-diff-line-file))
 	       (end (save-excursion
 		      (forward-line) ;; skip over "diff" line
@@ -1516,11 +1522,15 @@ Please see the manual for a complete description of Magit.
 	     (insert "\t" status-text "\n")
 	     (goto-char end)
 	     (let ((magit-section-hidden-default nil))
-		   (magit-wash-sequence #'magit-wash-hunk))
+	       (magit-wash-sequence #'magit-wash-hunk))))
-		 t)))))
+	 t)
 	(t
 	 nil)))
 
+(defun magit-wash-diff ()
+  (magit-with-section (magit-current-line) 'diff
+    (magit-wash-section-diff)))
+
 (defun magit-diff-item-kind (diff)
   (car (magit-section-info diff)))
 
@@ -1552,6 +1562,41 @@ Please see the manual for a complete description of Magit.
 	(t
 	 nil)))
 
+(defun magit-insert-diff (file)
+  (let ((cmd magit-git-executable)
+	(args (append magit-git-standard-options 
+		      (list "diff")
+		      magit-diff-options
+		      (list "--" file))))
+    (let ((p (point)))
+      (apply 'process-file cmd nil t nil args)
+      (if (not (eq (char-before) ?\n))
+	  (insert "\n"))
+      (save-restriction
+	(narrow-to-region p (point))
+	(goto-char p)
+	(magit-wash-diff-section)
+	(goto-char (point-max))))))
+
+(defun magit-wash-numstat-diffs ()
+  (magit-wash-sequence #'magit-wash-numstat-diff))
+
+(defun magit-wash-numstat-diff ()
+  (if (looking-at "\\(^[0-9-]+\\)\t\\([0-9-]+\\)\t\\(.*\\)$")
+      (let ((added (string-to-number (match-string 1)))
+	    (deleted (string-to-number (match-string 2)))
+	    (file (match-string-no-properties 3)))
+	(magit-with-section file 'diff
+	  (delete-region (point) (+ (line-end-position) 1))
+	  (if (or (not (magit-section-hidden magit-top-section))
+		  (< (+ added deleted) 20))
+	      (magit-insert-diff file)
+	    (magit-set-section-info (list 'modified file nil))
+	    (magit-set-section-needs-refresh-on-show t)
+	    (insert (format "\tModified %s (+%d -%d)\n" file added deleted))))
+	t)
+    nil))
+
 (defun magit-hunk-item-diff (hunk)
   (let ((diff (magit-section-parent hunk)))
     (or (eq (magit-section-type diff) 'diff)
@@ -1654,18 +1699,19 @@ Please see the manual for a complete description of Magit.
 
 (defun magit-insert-unstaged-changes (title)
   (let ((magit-hide-diffs t))
-    (magit-git-section 'unstaged title 'magit-wash-diffs
+    (let ((magit-diff-options '()))
-		       "diff" (magit-diff-U-arg))))
+      (magit-git-section 'unstaged title 'magit-wash-numstat-diffs
+			 "diff" "--numstat"))))
 
 (defun magit-insert-staged-changes (no-commit)
-  (let ((magit-hide-diffs t))
+  (let ((magit-hide-diffs t)
-    (if no-commit
+	(base (if no-commit
-        (let ((null-tree (magit-git-string "mktree </dev/null")))
+		  (magit-git-string "mktree </dev/null")
-          (magit-git-section 'staged "Staged changes:" 'magit-wash-diffs
+		"HEAD")))
-			     "diff" "--cached" (magit-diff-U-arg)
+    (let ((magit-diff-options '("--cached")))
-			     null-tree))
+      (magit-git-section 'staged "Staged changes:" 'magit-wash-numstat-diffs
-      (magit-git-section 'staged "Staged changes:" 'magit-wash-diffs
+			 "diff" "--cached" "--numstat"
-			 "diff" "--cached" (magit-diff-U-arg)))))
+			 base))))
 
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