git.el: Added a command to amend a commit.

It reverts the commit and sets up the status and edit log buffer to
allow making changes and recommitting it. Bound to C-c C-a.

Signed-off-by: Alexandre Julliard <julliard@winehq.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/emacs/git.el

@@ -740,6 +740,27 @@ Return the list of files that haven't been handled."
     (git-refresh-files)
     (git-refresh-ewoc-hf git-status)))
 
+(defun git-mark-files (status files)
+  "Mark all the specified FILES, and unmark the others."
+  (setq files (sort files #'string-lessp))
+  (let ((file (and files (pop files)))
+        (node (ewoc-nth status 0)))
+    (while node
+      (let ((info (ewoc-data node)))
+        (if (and file (string-equal (git-fileinfo->name info) file))
+            (progn
+              (unless (git-fileinfo->marked info)
+                (setf (git-fileinfo->marked info) t)
+                (setf (git-fileinfo->needs-refresh info) t))
+              (setq file (pop files))
+              (setq node (ewoc-next status node)))
+          (when (git-fileinfo->marked info)
+            (setf (git-fileinfo->marked info) nil)
+            (setf (git-fileinfo->needs-refresh info) t))
+          (if (and file (string-lessp file (git-fileinfo->name info)))
+              (setq file (pop files))
+            (setq node (ewoc-next status node))))))))
+
 (defun git-marked-files ()
   "Return a list of all marked files, or if none a list containing just the file at cursor position."
   (unless git-status (error "Not in git-status buffer."))
@@ -1218,7 +1239,8 @@ Return the list of files that haven't been handled."
       (goto-char (point-min))
       (when (re-search-forward "\n+\\'" nil t)
         (replace-match "\n" t t))
-      (when sign-off (git-append-sign-off committer-name committer-email)))))
+      (when sign-off (git-append-sign-off committer-name committer-email)))
+    buffer))
 
 (defun git-commit-file ()
   "Commit the marked file(s), asking for a commit message."
@@ -1251,6 +1273,52 @@ Return the list of files that haven't been handled."
       (setq buffer-file-coding-system coding-system)
       (re-search-forward (regexp-quote (concat git-log-msg-separator "\n")) nil t))))
 
+(defun git-setup-commit-buffer (commit)
+  "Setup the commit buffer with the contents of COMMIT."
+  (let (author-name author-email subject date msg)
+    (with-temp-buffer
+      (let ((coding-system (git-get-logoutput-coding-system)))
+        (git-call-process-env t nil "log" "-1" commit)
+        (goto-char (point-min))
+        (when (re-search-forward "^Author: *\\(.*\\) <\\(.*\\)>$" nil t)
+          (setq author-name (match-string 1))
+          (setq author-email (match-string 2)))
+        (when (re-search-forward "^Date: *\\(.*\\)$" nil t)
+          (setq date (match-string 1)))
+        (while (re-search-forward "^    \\(.*\\)$" nil t)
+          (push (match-string 1) msg))
+        (setq msg (nreverse msg))
+        (setq subject (pop msg))
+        (while (and msg (zerop (length (car msg))) (pop msg)))))
+    (git-setup-log-buffer (get-buffer-create "*git-commit*")
+                          author-name author-email subject date
+                          (mapconcat #'identity msg "\n"))))
+
+(defun git-get-commit-files (commit)
+  "Retrieve the list of files modified by COMMIT."
+  (let (files)
+    (with-temp-buffer
+      (git-call-process-env t nil "diff-tree" "-r" "-z" "--name-only" "--no-commit-id" commit)
+      (goto-char (point-min))
+      (while (re-search-forward "\\([^\0]*\\)\0" nil t 1)
+        (push (match-string 1) files)))
+    files))
+
+(defun git-amend-commit ()
+  "Undo the last commit on HEAD, and set things up to commit an
+amended version of it."
+  (interactive)
+  (unless git-status (error "Not in git-status buffer."))
+  (when (git-empty-db-p) (error "No commit to amend."))
+  (let* ((commit (git-rev-parse "HEAD"))
+         (files (git-get-commit-files commit)))
+    (git-call-process-env nil nil "reset" "--soft" "HEAD^")
+    (git-update-status-files (copy-sequence files) 'uptodate)
+    (git-mark-files git-status files)
+    (git-refresh-files)
+    (git-setup-commit-buffer commit)
+    (git-commit-file)))
+
 (defun git-find-file ()
   "Visit the current file in its own buffer."
   (interactive)
@@ -1329,6 +1397,7 @@ Return the list of files that haven't been handled."
 
 (unless git-status-mode-map
   (let ((map (make-keymap))
+        (commit-map (make-sparse-keymap))
         (diff-map (make-sparse-keymap))
         (toggle-map (make-sparse-keymap)))
     (suppress-keymap map)
@@ -1337,6 +1406,7 @@ Return the list of files that haven't been handled."
     (define-key map " "   'git-next-file)
     (define-key map "a"   'git-add-file)
     (define-key map "c"   'git-commit-file)
+    (define-key map "\C-c" commit-map)
     (define-key map "d"    diff-map)
     (define-key map "="   'git-diff-file)
     (define-key map "f"   'git-find-file)
@@ -1362,6 +1432,8 @@ Return the list of files that haven't been handled."
     (define-key map "x"   'git-remove-handled)
     (define-key map "\C-?" 'git-unmark-file-up)
     (define-key map "\M-\C-?" 'git-unmark-all)
+    ; the commit submap
+    (define-key commit-map "\C-a" 'git-amend-commit)
     ; the diff submap
     (define-key diff-map "b" 'git-diff-file-base)
     (define-key diff-map "c" 'git-diff-file-combined)