revlogdeltas: split candidate groups selection from the filtering logic
The group iteration has two main components:
* walking candidates, the logic that we are about to extend to build
intermediate snapshots,
* Making sure we test diffs against interesting bases. No duplicated tests,
skipping empty revisions, etc.
We split `_candidategroups` to separate the two components. This achieves two
goals:
* It will be simpler to update the walking logic for intermediate snapshots,
* We can gather the filtering logic from `finddeltainfo` into
`_candidategroups` to centralize it.
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 ..