D6407: relnotes: mention removed support for mixed log graph lines

[spectral (Kyle Lippincott)]

spectral accepted this revision.
spectral added inline comments.

INLINE COMMENTS

> next:25
> +   `experimental.graphstyle.grandparent = 3.` would use `!` for the
> +   first three lines of the graph and then `.`. This is now longer
> +   supported.

s/now/no

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D6407

To: martinvonz, #hg-reviewers, spectral
Cc: mercurial-devel