Add missing functions to contrib/emacs/vc-git.el

This is necessary to make several editing functions work, like
C-u C-x v =

Signed-off-by: David Kastrup <dak@gnu.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/contrib/emacs/vc-git.el b/contrib/emacs/vc-git.el
index e456ab9712e0574c712e5f79b0dc55cac167d9b1..b8f6be5c0af64dfbe7e136f984404f22aea68130 100644 (file)
--- a/contrib/emacs/vc-git.el
+++ b/contrib/emacs/vc-git.el
@@ -81,6 +81,71 @@
         (match-string 2 str)
       str)))
 
+(defun vc-git-symbolic-commit (commit)
+  "Translate COMMIT string into symbolic form.
+Returns nil if not possible."
+  (and commit
+       (with-temp-buffer
+        (and
+         (zerop
+          (call-process "git" nil '(t nil) nil "name-rev"
+                        "--name-only" "--tags"
+                        commit))
+         (goto-char (point-min))
+         (= (forward-line 2) 1)
+         (bolp)
+         (buffer-substring-no-properties (point-min) (1- (point-max)))))))
+
+(defun vc-git-previous-version (file rev)
+  "git-specific version of `vc-previous-version'."
+  (let ((default-directory (file-name-directory (expand-file-name file)))
+       (file (file-name-nondirectory file)))
+    (vc-git-symbolic-commit
+     (with-temp-buffer
+       (and
+       (zerop
+        (call-process "git" nil '(t nil) nil "rev-list"
+                      "-2" rev "--" file))
+       (goto-char (point-max))
+       (bolp)
+       (zerop (forward-line -1))
+       (not (bobp))
+       (buffer-substring-no-properties
+          (point)
+          (1- (point-max))))))))
+
+(defun vc-git-next-version (file rev)
+  "git-specific version of `vc-next-version'."
+  (let* ((default-directory (file-name-directory
+                            (expand-file-name file)))
+       (file (file-name-nondirectory file))
+       (current-rev
+        (with-temp-buffer
+          (and
+           (zerop
+            (call-process "git" nil '(t nil) nil "rev-list"
+                          "-1" rev "--" file))
+           (goto-char (point-max))
+           (bolp)
+           (zerop (forward-line -1))
+           (bobp)
+           (buffer-substring-no-properties
+            (point)
+            (1- (point-max)))))))
+    (and current-rev
+        (vc-git-symbolic-commit
+         (with-temp-buffer
+           (and
+            (zerop
+             (call-process "git" nil '(t nil) nil "rev-list"
+                           "HEAD" "--" file))
+            (goto-char (point-min))
+            (search-forward current-rev nil t)
+            (zerop (forward-line -1))
+            (buffer-substring-no-properties
+             (point)
+             (progn (forward-line 1) (1- (point))))))))))
+
 (defun vc-git-revert (file &optional contents-done)
   "Revert FILE to the version stored in the git repository."
   (if contents-done