mergestate: introduce a new ACTION_KEEP_NEW
`ACTION_KEEP` is overloaded and it's hard to figure out how we end up with this
KEEP, what was the state of things.
In a previous patch, we introduced `ACTION_KEEP_ABSENT` which represents files
which are kept absent in the working directory.
There is another special case where we keep the file when it's not present on
both ancestor and remote side. We introduce a dedicated action for that.
The goal is to use these information to make bid merge smarter.
Differential Revision: https://phab.mercurial-scm.org/D9002
Issue1678: IndexError when pushing
setting up base repo
$ hg init a
$ cd a
$ touch a
$ hg ci -Am a
adding a
$ cd ..
cloning base repo
$ hg clone a b
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd b
setting up cset to push
$ hg up null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ touch a
different msg so we get a clog new entry
$ hg ci -Am b
adding a
created new head
pushing
$ hg push -f ../a
pushing to ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 0 changes to 0 files (+1 heads)
$ cd ..