Fixes T8236. I played around with a lot of variations of this but in the end it felt like the simple version was best.
- Maniphest Tasks
- T8236: `arc weld` should do something
- rARC8fe1d7701e5d: (stable) Promote 2018 Week 7
rARCbe1dd7e2ba23: Robustly fuse files together with `arc weld`
Ran arc weld a.txt b.txt, observed very robust fusion of materials.