bug#34532: Unhandled errors in vc

[Juri Linkov]

> After ‘C-x v g’ (vc-annotate) typing ‘a’ 
> (vc-annotate-revision-previous-to-line)
> in the *Annotate* buffer on the earliest (initial) revision fails with:
>
>   Debugger entered--Lisp error: (error "Invalid argument to 
> vc-annotate-warp-revision")
>     signal(error ("Invalid argument to vc-annotate-warp-revision"))
>     error("Invalid argument to vc-annotate-warp-revision")
>     vc-annotate-warp-revision(nil "...")

This is now fixed.

Another problem is that ‘vc-root-version-diff’ can't be used when
fileset is not available.  But this command doesn't use fileset,
it uses the root directory, so this patch adds an optional
arg ‘fileset’ to ‘vc-diff-build-argument-list-internal’,
so ‘vc-root-version-diff’ can provide its own fake fileset
with the root directory:

diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index aae21ec45a..0a638ec7d7 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -1762,9 +1762,9 @@ vc-read-revision
                          nil nil initial-input 'vc-revision-history default)
       (read-string prompt initial-input nil default))))
 
-(defun vc-diff-build-argument-list-internal ()
+(defun vc-diff-build-argument-list-internal (&optional fileset)
   "Build argument list for calling internal diff functions."
-  (let* ((vc-fileset (vc-deduce-fileset t)) ;FIXME: why t?  --Stef
+  (let* ((vc-fileset (or fileset (vc-deduce-fileset t))) ;FIXME: why t?  --Stef
          (files (cadr vc-fileset))
          (backend (car vc-fileset))
          (first (car files))
@@ -1815,7 +1815,11 @@ vc-version-diff
 ;;;###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))
+  (interactive
+   (vc-diff-build-argument-list-internal
+    (or (ignore-errors (vc-deduce-fileset t))
+        (let ((backend (or (vc-deduce-backend) (vc-responsible-backend 
default-directory))))
+          (list backend (list (vc-call-backend backend 'root 
default-directory)))))))
   ;; This is a mix of `vc-root-diff' and `vc-version-diff'
   (when (and (not rev1) rev2)
     (error "Not a valid revision range"))