filectx: add an overlayfilectx class...
filectx: add an overlayfilectx class
The end goal is to make it possible to avoid potential expensive fctx.data()
when unnecessary.
While memctx is useful for creating new file contexts, there are many cases
where we could reuse an existing raw file revision (amend, histedit, rebase,
process a revision constructed by a remote peer, etc). The overlayfilectx
class is made to support such reuse cases. Together with a later patch, hash
calculation and expensive flag processor could be avoided.
