On 11/28/15 18:09, Dmitry Gutov wrote:

Please try this definition and see if it resolves the problem:

(defun vc-hg-previous-revision (_file rev)
(let ((newrev (1- (string-to-number rev))))
    (when (>= newrev 0)
      (with-temp-buffer
        (vc-hg-command t 0 nil
                       "id" "--hidden" "-n" "-r"
                       (format "first(%d:0 and not hidden())" newrev))
        ;; Trim the trailing newline.
        (buffer-substring (point-min) (1- (point-max)))))))

This says to look at all non-hidden revs from X down to zero, choose the
first one, and print its numeric rev number. If the current rev is X+1,
that gives the first previous non-hidden rev. But I'm sure there must
be a better way, without having to examine all previous changesets.

If you anticipated that we'd have to make one process call per revision, then I think the above definition does better.

I tried this, and it works fine. But I discovered another problem for VC with the changeset evolution features: if a repository has any changesets that are marked 'obsolete', and any mercurial command is issued by a user who hasn't enabled the extension, a warning message is printed to stderr:

obsolete feature not enabled but <N> markers found!

If VC grabs this output as part of the mercurial response, and uses it in subsequent commands, it (unsurprisingly) fails:

hg: parse error at 9: invalid token

Looking at mercurial sources, there's no way to suppress this warning. I guess one workaround would be to have vc-hg-command skip over it if it's there.

Glenn