`arc patch --nocommit --nobranch` is buggy

[thomie]

Currently, harbormaster chokes on D1187 with Usage Exception: Unable to apply patch!.

The funny thing is, the following commands all work:

• arc patch D1187
• arc patch --nocommit D1187
• arc patch --nobranch D1187

The only command that doesn't work is:

• arc patch --nocommit --nobranch D1187

This happens to be the command that run.sh uses.

I don't understand what's going on, but the workaround is easy: don't use --nocommit and --nobranch at the same time.

[thomie]

The current state of the branch I used to to create D1187 is saved here, in case you want to investigate or report upstream: https://github.com/thomie/ghc/tree/arc-bug-nocommit-nobranch

Edit: to reproduce, create a Diff from that branch using arc diff HEAD^.

The problem is that the 2 patches have a small overlap, which arc patch can handle just fine, but arc patch --nobranch --nocommit can not.

[adamse]

Possibly related error in this build: https://phabricator.haskell.org/harbormaster/build/6282/?l=0