For some reason, in 2018 i bookmarked it as a Mercurial thing. -- A Vim plugin which shows git diff markers in the sign column and stages/previews/undoes hunks and partial hunks. - GitHub - airblade/vim-gitgutter: A Vim plugin which shows git diff markers in the sign column and stages/previews/undoes hunks and partial hunks.
Backout is basically four steps rolled into one:
hg update -C -r <rev-to-backout>
hg revert --all -r <parent of rev-to-backout>
hg commit
hg update -C -r <startrev>
There's a fifth step that is done automatically if you specify --merge :
hg merge (merges <startrev> with the newly committed rev from 3.)