Aha, that helps. And looking further at https://phabricator.haskell.org/D202, I can see under "Revision update history" that there are four diffs all stashed in this on Phab ticket. (That contradicts my previous model which was one patch per Phab ticket; people have been complaining about that.) So my new questions are: * How can I apply "Diff 1" or "Diff 2"? Using "arc patch" only applies "Diff 4" * How can I apply all of "Diff 1" ... "Diff 4" in one go? Simon | -----Original Message----- | From: Herbert Valerio Riedel [mailto:hvriedel@gmail.com] | Sent: 07 October 2014 10:05 | To: Simon Peyton Jones | Cc: ghc-devs@haskell.org | Subject: Re: Phabricator guidance | | 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...