bug#68364: Print log buttons fail with vc-log-mergebase

[Dmitry Gutov <dmitry@gutov.dev>]

On 10/01/2024 19:20, Juri Linkov wrote:
>>> Buttons to show more log entries is a nice feature,
>>> but after the recent change this doesn't work with
>>> 'C-x v M L' (vc-log-mergebase):
>>>     Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p
>>> "branch-2")
>>>       vc-print-log-setup-buttons("branch-1" t "branch-2" nil)
>>> Probably it requires a special handling for 'C-x v M L'.
>>
>> Does this help?
>>
>> Looks like the description of the LIMIT argument wasn't updated in the
>> vc-print-log-internal's docstring, when it started to be a string
>> sometimes.
> 
> The description of the LIMIT argument in vc-print-log-internal looks strange:
> 
>    "Show up to LIMIT entries (non-nil means unlimited)."
> 
> Maybe it should be "(nil means unlimited)"?

Probably. And a mention of allowed string values.

>> diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
>> index b8cc44fc3dc..7d5a5486250 100644
>> --- a/lisp/vc/vc.el
>> +++ b/lisp/vc/vc.el
>> @@ -2711,7 +2711,7 @@ vc-print-log-setup-buttons
>>     ;; In either case only one revision is wanted, no buttons.
>>     (when (and limit (not (eq 'limit-unsupported pl-return))
>>                (not (and is-start-revision
>> -                       (= limit 1))))
>> +                       (eql limit 1))))
>>       (let ((entries 0))
>>         (goto-char (point-min))
>>         (while (re-search-forward log-view-message-re nil t)
> 
> Sorry, still fails on another line:
> 
>        (if (< entries limit)
> 
> But this works:
> 
> diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
> index b8cc44fc3dc..d284b19fcf0 100644
> --- a/lisp/vc/vc.el
> +++ b/lisp/vc/vc.el
> @@ -2709,7 +2709,8 @@ vc-print-log-setup-buttons
>     ;; LIMIT=1 is set by vc-annotate-show-log-revision-at-line
>     ;; or by vc-print-root-log with current-prefix-arg=1.
>     ;; In either case only one revision is wanted, no buttons.
> -  (when (and limit (not (eq 'limit-unsupported pl-return))
> +  (when (and limit (not (stringp limit))
> +             (not (eq 'limit-unsupported pl-return))
>                (not (and is-start-revision
>                          (= limit 1))))
>       (let ((entries 0))

That would mean the "follow renames" button is never shown in 
vc-log-mergebase outputs.

I've pushed commit 1ecb53ad2fc, check it out.