Re: bisect: "Needed a single revision" message is confusing

> Hi,
> 
> Suppose I'm doing a git bisect, say:
> 
> $ git bisect good 8c7a786b6c8eae8eac91083cdc9a6e337bc133b0
> 
> That works fine. The sha1 could also be a substring, as long as it's
> unambiguous, e.g.:
> 
> $ git bisect good 8c7a786b6c
> 
> Now if it's ambiguous, I get an error message:
> 
> $ git bisect good 8
> fatal: Needed a single revision
> Bad rev input: 8
> 
> All fine and good. But what if I somehow input a non-existing sha1 (in
> my case see [1]), e,g:
> 
> $ git bisect good 8c7a786b6c8eae8eac91083cdc9a6e337bc133b1
> fatal: Needed a single revision
> Bad rev input: 8c7a786b6c8eae8eac91083cdc9a6e337bc133b1
> 
> I understand that technically both "no revision" and "multiple
> revisions" qualify as "not a single revision", but they correspond to
> quite different situations. I think it would be more helpful to get
> different error messages, something like:
> 
> Bad rev input: 8 refers to multiple revisions
> Bad rev input: 8c7a786b6c8eae8eac91083cdc9a6e337bc133b1 does not refer
> to a valid revision
> 
> (and avoid outputing the "fatal: Needed a single revision" message).
> 
> Is this a good idea? Anybody can think of better error messages?
> 
> I'm not familiar with the code base at all, but I could give a try at
> implementing it, unless it's trivial enough that someone does it
> earlier. After a quick look, it looks like either git-bisect itself or
> rev-parse would need to be touched, any pointers and hints welcome.
> 
> Cheers,
> 
> Daniel
> 
> [1] if you want to know, I got a sha1 from one repository and used it
> in another, which probably should work, except that when using git-svn
> they don't. And the "single revision" error message lead me on a
> tangent.
>