bug#33650: 27.0.50; Root diffs between revisions

[Juri Linkov]

>> > Finally, we need documentation changes to go with this change of
>> > user-visible behavior.
>>
>> This feature is already documented in (info "(emacs) Old Revisions")
>>
>>   ‘C-x v D’
>>        Compare the entire working tree to the revision you started from
>>        (‘vc-root-diff’).  With a prefix argument, prompt for two revisions
>>        and compare their trees.
>>
>> It didn't work as documented before properly implemented by the patch.
>
> Isn't the result user-visible change in behavior?

Yes, this fix changes user-visible behavior, so perhaps it should be
mentioned in NEWS.

>>  (defun vc-version-diff (_files rev1 rev2)
>> -  "Report diffs between revisions of the fileset in the repository history."
>> +  "Report diffs between revisions of the fileset in the repository history.
>> +REV1 is an older revision, REV2 is a newer revision."
>
> We usually mention the arguments in the first line of the doc string.
> Something like this:
>
>   Report diffs between revisions REV1 and REV2 in the repository history.
>
> I wonder whether "fileset" needs to be mentioned at all, given your
> changes.  When does any "fileset" come into play here?

"fileset" is essential to be mentioned in `vc-version-diff'
whereas the text "in the repository history" is unnecessary.

>> +(defun vc-root-version-diff (_files rev1 rev2)
>> +  "Report diffs between revisions of the whole tree in the repository 
>> history.
>> +REV1 is an older revision, REV2 is a newer revision."
>
> Same here: please mention the arguments in the first sentence.

As "fileset" is essential for `vc-version-diff',
"whole tree" is essential for `vc-root-version-diff':

diff --git a/doc/emacs/maintaining.texi b/doc/emacs/maintaining.texi
index 4527c23d9e..e92db9e419 100644
--- a/doc/emacs/maintaining.texi
+++ b/doc/emacs/maintaining.texi
@@ -774,8 +774,7 @@ Old Revisions
 
 @item C-x v D
 Compare the entire working tree to the revision you started from
-(@code{vc-root-diff}).  With a prefix argument, prompt for two
-revisions and compare their trees.
+(@code{vc-root-diff}).
 
 @item C-x v ~
 Prompt for a revision of the current file, and visit it in a separate
@@ -829,7 +828,9 @@ Old Revisions
 it displays the changes in the entire current working tree (i.e., the
 working tree containing the current VC fileset).  If you invoke this
 command from a Dired buffer, it applies to the working tree containing
-the directory.
+the directory.  With a prefix argument, prompt for two revisions and
+compare the entire version-controlled directory trees (RCS, SCCS, CVS,
+and SRC do not support this feature).
 
 @vindex vc-diff-switches
   You can customize the @command{diff} options that @kbd{C-x v =} and
@@ -963,6 +964,7 @@ VC Change Log
 Directory Mode}) or a Dired buffer (@pxref{Dired}), it applies to the
 file listed on the current line.
 
+@kindex C-x v L
 @findex vc-print-root-log
 @findex log-view-toggle-entry-display
   @kbd{C-x v L} (@code{vc-print-root-log}) displays a
diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index dbbc3e2038..5ff9f4d5be 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -1817,7 +1817,7 @@ vc-diff-build-argument-list-internal
 
 ;;;###autoload
 (defun vc-version-diff (_files rev1 rev2)
-  "Report diffs between revisions of the fileset in the repository history."
+  "Report diffs between REV1 and REV2 revisions of the fileset."
   (interactive (vc-diff-build-argument-list-internal))
   ;; All that was just so we could do argument completion!
   (when (and (not rev1) rev2)
@@ -1827,6 +1827,28 @@ vc-version-diff
   (vc-diff-internal t (vc-deduce-fileset t) rev1 rev2
                    (called-interactively-p 'interactive)))
 
+;;;###autoload
+(defun vc-root-version-diff (_files rev1 rev2)
+  "Report diffs between REV1 and REV2 revisions of the whole tree."
+  (interactive (vc-diff-build-argument-list-internal))
+  ;; This is a mix of `vc-root-diff' and `vc-version-diff'
+  (when (and (not rev1) rev2)
+    (error "Not a valid revision range"))
+  (let ((backend (vc-deduce-backend))
+        (default-directory default-directory)
+        rootdir)
+    (if backend
+        (setq rootdir (vc-call-backend backend 'root default-directory))
+      (setq rootdir (read-directory-name "Directory for VC root-diff: "))
+      (setq backend (vc-responsible-backend rootdir))
+      (if backend
+          (setq default-directory rootdir)
+        (error "Directory is not version controlled")))
+    (let ((default-directory rootdir))
+      (vc-diff-internal
+       t (list backend (list rootdir)) rev1 rev2
+       (called-interactively-p 'interactive)))))
+
 ;;;###autoload
 (defun vc-diff (&optional historic not-urgent)
   "Display diffs between file revisions.
@@ -1900,10 +1922,8 @@ vc-root-diff
 saving the buffer."
   (interactive (list current-prefix-arg t))
   (if historic
-      ;; FIXME: this does not work right, `vc-version-diff' ends up
-      ;; calling `vc-deduce-fileset' to find the files to diff, and
-      ;; that's not what we want here, we want the diff for the VC root dir.
-      (call-interactively 'vc-version-diff)
+      ;; We want the diff for the VC root dir.
+      (call-interactively 'vc-root-version-diff)
     (when buffer-file-name (vc-buffer-sync not-urgent))
     (let ((backend (vc-deduce-backend))
          (default-directory default-directory)