Re: backwards compatibility, was Re: [PATCH v1 1/3] Introduce config variable "diff.primer"

[Keith Cascio <keith@CS.UCLA.EDU>]

On Mon, 26 Jan 2009, Jeff King wrote:

> Yep, that's what defaults are. And guess what: we _already_ have the same 
> thing. I have diff.renames set in my ~/.gitconfig. That does _exactly_ what
> 
>   git config --global diff.primer -M
> 
> would do. It's just a syntax that saves us from having to introduce a boatload 
> of new variables, one per command line option.


Great point, IOW, primer magnifies already existing pitfalls.  I like that about 
primer v1, however unsatisfying it is otherwise.  Rather than stick a piece of 
chewing gum in that chink in the dam, let's repair it and get the whole darn 
thing ready for the 21st century while we're at it.

> However, there are two other drawbacks of aliases that I can think of:
>   1. They are tied to a specific command, whereas diff options are tied
>      to the concept of diffing. So now I have to write an alias (with a
>      new name) for each command:
>        git config alias.mylog 'log -w'
>        git config alias.mydiff 'diff -w'
>        git config alias.myshow 'show -w'
>   2. They can't change defaults based on the file to be diffed. One of
>      the things Keith mentioned (and I don't remember if this was
>      implemented in his patch series) was supporting this for
>      gitattributes diff drivers. How do I do
>        git config diff.tex.primer -w
>      using aliases?

This scenario was specifically part of my motivation for imagining primer v1 as 
I did.

> But now you have me defending Keith's proposal

And well.

> which he should be doing himself ;P

True.  I'm at the point here where I will demand of myself one of two outcomes.  
Either I:

(1) Satisfy myself on a deep, foundational level why the inescapable structure 
of not just this particularly well-constituted software project (Git!), but 
software projects in general, since surely many a fearless development team has 
braved this philosophical sticky place before us, prevents one from getting 
everything one wants, i.e. forces a compromise, a.k.a. the "no silver bullet" 
interpretation.

(2) Write primer patch v2 that somehow does THE RIGHT THING, also satisfying on 
a deep level to at least myself, a.k.a. the silver bullet.

                                            -- Keith