Phabricator guidance

[Herbert Valerio Riedel]

On 2014-10-07 at 10:57:00 +0200, Simon Peyton Jones wrote:
> I suppose I will have to look at this. But I have no clue how to do so.
>
> D202 itself seems to be a very small patch (only ten lines or so), so presumably it applies on top of some other patch?  But what?
>
> Someone said I could use
> 	arc patch D202
> to apply the patch in my own tree, which is crucial for reproducing
> the error that Jan is stuck on.  

> BUT the patch presumably applies to a
> particular commit, NOT the head of my current tree.  But what is the
> base commit to which it applies?  Does arc patch check out the base
> commit before applying?

If you actually perform 'arc patch D202', this is the output you
currently get:


,----
| Created and checked out branch arcpatch-D202.
| 
| 
|     This diff is against commit 3e17822f5f4e4d2f582dc0a053f532125f9777c7, but
|     the commit is nowhere in the working copy. Try to apply it against the
|     current working copy state? (3549c952b535803270872adaf87262f2df0295a4)
|     [Y/n] n
`----

So yes, 'arc' tries apply the code-revision on top of the commit is was
based on; and in this case, it is actually missing from ghc.git :-/

What's more, you can also declare that a code-revisions builds on top of
another code-revision, in which case 'arc' will automatically try to
(recursively) apply that other code-revision to your source-tree first, before
applying the one you are actually requesting on top.


I hope Austin or someone else may chime in to provide further assistance
if this doesn't help...