Improve handling of the first Git revision

* lisp/vc/log-view.el (log-view-toggle-entry-display): When
there's no next entry, delete until the end of the buffer.
(log-view-end-of-defun-1): Stop at eob.

* lisp/vc/vc-annotate.el
(vc-annotate-show-diff-revision-at-line-internal): Don't give up
when previous-revision is nil.

* lisp/vc/vc-git.el (vc-git-expanded-log-entry): End the arguments
with `--' to avoid ambiguity.
(vc-git-annotate-extract-revision-at-line): Exclude `^' from the
returned revision string.
(vc-git-annotate-time): Expect `^' before the first revision.

* lisp/vc/vc-git.el (vc-git-diff): Diff against an empty tree if
REV1 is nil, and REV2 is not.

* lisp/vc/vc.el: Update the description of the `diff' function.

4 files changed, 30 insertions, 21 deletions

diff --git a/lisp/vc/log-view.el b/lisp/vc/log-view.el
index 042ea131a97..19bbc45f927 100644
--- a/lisp/vc/log-view.el
+++ b/lisp/vc/log-view.el
@@ -404,7 +404,9 @@ This calls `log-view-expanded-log-entry-function' to do the work."
               (unless (and pos (log-view-inside-comment-p pos))
                 (error "Broken markup in `log-view-toggle-entry-display'"))
               (delete-region pos
-                             (next-single-property-change pos 'log-view-comment))
+                             (or
+                              (next-single-property-change pos 'log-view-comment)
+                              (point-max)))
               (put-text-property beg (1+ beg) 'log-view-entry-expanded nil)
               (if (< opoint pos)
                   (goto-char opoint)))
@@ -469,7 +471,10 @@ It assumes that a log entry starts with a line matching
        ((looking-back "Show 2X entries    Show unlimited entries"
                       (line-beginning-position))
         (setq looping nil)
-        (forward-line -1))))))
+        (forward-line -1))
+       ;; There are no buttons if we've turned on unlimited entries.
+       ((eobp)
+        (setq looping nil))))))
 
 (defun log-view-end-of-defun (&optional arg)
   "Move forward to the next Log View entry.
diff --git a/lisp/vc/vc-annotate.el b/lisp/vc/vc-annotate.el
index d369c90915a..3a50c9b6a2d 100644
--- a/lisp/vc/vc-annotate.el
+++ b/lisp/vc/vc-annotate.el
@@ -582,17 +582,15 @@ the file in question, search for the log entry required and move point."
         (setq prev-rev
               (vc-call-backend vc-annotate-backend 'previous-revision
                                (if filediff fname nil) rev))
-        (if (not prev-rev)
-            (message "Cannot diff from any revision prior to %s" rev)
-          (vc-diff-internal
-           t
-           ;; The value passed here should follow what
-           ;; `vc-deduce-fileset' returns.
-           (list vc-annotate-backend
-                 (if filediff
-                     (list fname)
-                   nil))
-           prev-rev rev))))))
+        (vc-diff-internal
+         t
+         ;; The value passed here should follow what
+         ;; `vc-deduce-fileset' returns.
+         (list vc-annotate-backend
+               (if filediff
+                   (list fname)
+                 nil))
+         prev-rev rev)))))
 
 (defun vc-annotate-show-diff-revision-at-line ()
   "Visit the diff of the revision at line from its previous revision."
diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index cbf3da3003f..e3cd5d4e3dc 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -960,14 +960,13 @@ or BRANCH^ (where \"^\" can be repeated)."
 
 (defun vc-git-expanded-log-entry (revision)
   (with-temp-buffer
-    (apply 'vc-git-command t nil nil (list "log" revision "-1"))
+    (apply 'vc-git-command t nil nil (list "log" revision "-1" "--"))
     (goto-char (point-min))
     (unless (eobp)
       ;; Indent the expanded log entry.
       (indent-region (point-min) (point-max) 2)
       (buffer-string))))
 
-
 (defun vc-git-region-history (file buffer lfrom lto)
   (vc-git-command buffer 'async nil "log" "-p" ;"--follow" ;FIXME: not supported?
                   (format "-L%d,%d:%s" lfrom lto (file-relative-name file))))
@@ -1019,12 +1018,18 @@ or BRANCH^ (where \"^\" can be repeated)."
 
 (defun vc-git-diff (files &optional rev1 rev2 buffer async)
   "Get a difference report using Git between two revisions of FILES."
-  (let (process-file-side-effects)
+  (let (process-file-side-effects
+        (command "diff-tree"))
+    (if rev2
+        ;; Diffing against the empty tree.
+        (unless rev1 (setq rev1 "4b825dc642cb6eb9a060e54bf8d69288fbee4904"))
+      (setq command "diff-index")
+      (unless rev1 (setq rev1 "HEAD")))
     (if vc-git-diff-switches
         (apply #'vc-git-command (or buffer "*vc-diff*")
                (if async 'async 1)
                files
-               (if (and rev1 rev2) "diff-tree" "diff-index")
+               command
                "--exit-code"
                (append (vc-switches 'git 'diff)
                        (list "-p" (or rev1 "HEAD") rev2 "--")))
@@ -1033,7 +1038,7 @@ or BRANCH^ (where \"^\" can be repeated)."
                       (concat "diff "
                               (mapconcat 'identity
                                          (vc-switches nil 'diff) " "))
-                      (or rev1 "HEAD") rev2 "--"))))
+                      rev1 rev2 "--"))))
 
 (defun vc-git-revision-table (_files)
   ;; What about `files'?!?  --Stef
@@ -1061,7 +1066,7 @@ or BRANCH^ (where \"^\" can be repeated)."
 (declare-function vc-annotate-convert-time "vc-annotate" (&optional time))
 
 (defun vc-git-annotate-time ()
-  (and (re-search-forward "^[0-9a-f]+[^()]+(.*?\\([0-9]+\\)-\\([0-9]+\\)-\\([0-9]+\\) \\(:?\\([0-9]+\\):\\([0-9]+\\):\\([0-9]+\\) \\([-+0-9]+\\)\\)? *[0-9]+) " nil t)
+  (and (re-search-forward "^[0-9a-f^]+[^()]+(.*?\\([0-9]+\\)-\\([0-9]+\\)-\\([0-9]+\\) \\(:?\\([0-9]+\\):\\([0-9]+\\):\\([0-9]+\\) \\([-+0-9]+\\)\\)? *[0-9]+) " nil t)
        (vc-annotate-convert-time
         (apply #'encode-time (mapcar (lambda (match)
                                        (if (match-beginning match)
@@ -1072,7 +1077,7 @@ or BRANCH^ (where \"^\" can be repeated)."
 (defun vc-git-annotate-extract-revision-at-line ()
   (save-excursion
     (beginning-of-line)
-    (when (looking-at "\\([0-9a-f^][0-9a-f]+\\) \\(\\([^(]+\\) \\)?")
+    (when (looking-at "\\^?\\([0-9a-f]+\\) \\(\\([^(]+\\) \\)?")
       (let ((revision (match-string-no-properties 1)))
         (if (match-beginning 2)
             (let ((fname (match-string-no-properties 3)))
diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index d5d0abe6517..1bd04e13430 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -367,7 +367,8 @@
 ;;   BUFFER is nil.  If ASYNC is non-nil, run asynchronously.  If REV1
 ;;   and REV2 are non-nil, report differences from REV1 to REV2.  If
 ;;   REV1 is nil, use the working revision (as found in the
-;;   repository) as the older revision; if REV2 is nil, use the
+;;   repository) as the older revision if REV2 is nil as well;
+;;   otherwise, diff against an empty tree.  If REV2 is nil, use the
 ;;   current working-copy contents as the newer revision.  This
 ;;   function should pass the value of (vc-switches BACKEND 'diff) to
 ;;   the backend command.  It should return a status of either 0 (no