feature/package+vc d33998ed3b 09/10: Have 'last-change' accept a line number instead of a range

[Philip Kaludercic]

branch: feature/package+vc
commit d33998ed3b5e05a40b9c4c1799b6e911b582ef01
Author: Philip Kaludercic <philipk@posteo.net>
Commit: Philip Kaludercic <philipk@posteo.net>

    Have 'last-change' accept a line number instead of a range
    
    * lisp/emacs-lisp/package-vc.el (package-vc-release-rev): Use new
    signature.
    * lisp/vc/vc-git.el (vc-git-last-change): Update signature
    * lisp/vc/vc.el (vc-default-last-change): Update signature and use
    'annotate-command'.
---
 lisp/emacs-lisp/package-vc.el |  4 ++--
 lisp/vc/vc-git.el             | 10 +++-------
 lisp/vc/vc.el                 | 29 ++++++++++++++++-------------
 3 files changed, 21 insertions(+), 22 deletions(-)

diff --git a/lisp/emacs-lisp/package-vc.el b/lisp/emacs-lisp/package-vc.el
index c3f54c1be8..52e7e25e9f 100644
--- a/lisp/emacs-lisp/package-vc.el
+++ b/lisp/emacs-lisp/package-vc.el
@@ -507,8 +507,8 @@ If no such revision can be found, return nil."
           (ignore-error vc-not-supported
             (vc-call-backend (vc-backend (buffer-file-name))
                              'last-change
-                             (match-beginning 0)
-                             (match-end 0))))))))
+                             (buffer-file-name)
+                             (line-number-at-pos nil t))))))))
 
 ;;;###autoload
 (defun package-vc-install (name-or-url &optional name rev backend)
diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index cd62effd08..376892c720 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -1632,17 +1632,13 @@ This requires git 1.8.4 or later, for the \"-L\" option 
of \"git log\"."
                    (expand-file-name fname (vc-git-root default-directory))))
          revision)))))
 
-(defun vc-git-last-change (from to)
+(defun vc-git-last-change (file line)
   (vc-buffer-sync)
-  (let ((file (file-relative-name
-               (buffer-file-name)
-               (vc-git-root (buffer-file-name))))
-        (start (line-number-at-pos from t))
-        (end (line-number-at-pos to t)))
+  (let ((file (file-relative-name file (vc-git-root (buffer-file-name)))))
     (with-temp-buffer
       (when (vc-git--out-ok
              "blame" "--porcelain"
-             (format "-L%d,%d" start end)
+             (format "-L%d,+1" line)
              file)
         (goto-char (point-min))
         (save-match-data
diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index c8d28c144b..d655a1c625 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -449,10 +449,10 @@
 ;;
 ;;   Return the common ancestor between REV1 and REV2 revisions.
 ;;
-;; - last-change (from to)
+;; - last-change (file line)
 ;;
-;;   Return the most recent revision that made a change between FROM
-;;   and TO.
+;;   Return the most recent revision of FILE that made a change
+;;   on LINE.
 
 ;; TAG/BRANCH SYSTEM
 ;;
@@ -3590,17 +3590,20 @@ it indicates a specific revision to check out."
             (throw 'ok res)))))))
 
 (declare-function log-view-current-tag "log-view" (&optional pos))
-(defun vc-default-last-change (_backend from to)
+(defun vc-default-last-change (_backend file line)
   "Default `last-change' implementation.
-FROM and TO are used as region markers"
-  (save-window-excursion
-    (let* ((buf (window-buffer (vc-region-history from to)))
-           (proc (get-buffer-process buf)))
-      (cl-assert (processp proc))
-      (while (accept-process-output proc))
-      (with-current-buffer buf
-        (prog1 (log-view-current-tag)
-          (kill-buffer))))))
+It returns the last revision that changed LINE number in FILE."
+  (unless (file-exists-p file)
+    (signal 'file-error "File doesn't exist"))
+  (with-temp-buffer
+    (vc-call-backend (vc-backend file) 'annotate-command
+                     file (current-buffer))
+    (goto-char (point-min))
+    (forward-line (1- line))
+    (let ((rev (vc-call-backend
+                (vc-backend file)
+                'annotate-extract-revision-at-line)))
+      (if (consp rev) (car rev) rev))))