D7982: rust-utils: introduce `subslice_index` function

[martinvonz (Martin von Zweigbergk)]

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martinvonz added a comment.
martinvonz requested changes to this revision.


  Sorry to be dismissive, but please hold on to it until it becomes needed then. I'm strongly against adding dead code unless we know we're at least going to use it soon.

REPOSITORY
  rHG Mercurial

CHANGES SINCE LAST ACTION
  https://phab.mercurial-scm.org/D7982/new/

REVISION DETAIL
  https://phab.mercurial-scm.org/D7982

To: Alphare, #hg-reviewers, martinvonz
Cc: martinvonz, kevincox, mercurial-devel