How to reopen a closed "arc diff"?

Question

Our team uses Git for code management & Phabricator's Differential tool, and the command-line tool Arcanist on each developer's machine, to generate nice-looking code-review dashboards. I created a diff D1 and it got successfully closed after being reviewed by my fellow developer. I created another branch from a separate git branch B2. Merged the code from the closed revision D1. When I tried to create a new diff D2 using arc diff, I get the error

Exception ERR_CLOSED: This revision has already been closed.

Is there a way to create a new diff D2.

Answer 1

If somehow you cannot create a new diff, even using arc diff --create, Perhaps you have a saved revision message fom earlier arc diff executions in .git/arc/create-message, with a line that say

Differential Revision: ... (some url)

Try to delete that line, or just an url after the colon. According to this comment and my experience, this can help.