bug#16897: 24.3.50; vc-print-root-log doesn't show the top commit if it's a merge commit

[Dmitry Gutov]

On 28.02.2014 19:24, Stefan Monnier wrote:
> > > Yes, something like that is needed for other circumstances as well,
> > Do you mean other uses of `vc-git-print-log'?
>
> No: other circumstances where we pass a list of files to Git.
> IOW, maybe vc-git-command should support turning a (list
> default-directory) into nil.

This sort of assumes that default-directory is always the root dir. 
Which isn't true.

Of course it seems that in practice, whenever file-or-list is the same 
as (list default-directory), the latter *is* the root dir. But that's a 
shaky assumption.

I'm not sure I want to spend another process call to determine what the 
actual root dir is each time, so maybe we should limit the fix to 
`vc-git-print-log'.

At least, until any other command is known to exhibit a similar bug.