manifest: change manifestctx to not inherit from manifestdict
If manifestctx inherits from manifestdict, it requires some weird logic to
lazily load the dict if a piece of information is asked for. This ended up being
complicated and unintuitive to use.
Let's move the dict creation to .read(). This will make even more sense once we
start adding readdelta() and other similar methods to manifestctx.
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 ..