Possible to mark a task as a duplicate of another twice

IMPORTANT

  • Bug reports MUST include reproduction instructions which allow someone who does not have access to your environment to reproduce the issue you’re encountering.
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Reproduction Instructions

  • Create 2 tasks
  • Close T1 as a duplicate of T2
  • Go back to T1 and close as a duplicate of T2
    This should in my opinion produce an error saying that this task has already been merged into T2.
    See https://phab.wmflabs.org/T80
    Phabricator/Arcanist Version
    Output from Config > Version Information or arc version.
    82a0d4251ae61e2387d9e4abc17992db8c9e40db (Feb 12 2020)

This is intended behavior. Tasks may be merged into other tasks zero or more times, and the tasks they are merged into do not need to be unique.

Legitimate workflows may involve merging A into B multiple times. Although this specific case (two merges in a row, with no reopen between them) is probably a mistake, the cost of the mistake is very low and the complexity of detecting it is relatively high.

Fair enough. Seemed weird to me.