mergedriver: delete it
The merge driver code was added in late 2015. I think
'406a654b::6f045b56 & user("sid0")' is a reasonable revset for finding
the relevant commits, including preparation for it. The code is very
poorly tested, which makes it very hard to maintain. It seems it's
only used by FB and they don't use this code base anymore, so let's
remove the code to make it easier for us to maintain our product.
Differential Revision: https://phab.mercurial-scm.org/D9041
$ hg init repo
$ cd repo
$ touch foo
$ hg ci -Am 'add foo'
adding foo
$ hg up -C null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
this should be stored as a delta against rev 0
$ echo foo bar baz > foo
$ hg ci -Am 'add foo again'
adding foo
created new head
$ hg debugindex foo
rev linkrev nodeid p1 p2
0 0 b80de5d13875 000000000000 000000000000
1 1 0376abec49b8 000000000000 000000000000
$ cd ..