hg-core: make parse_dirstate return references rather than update hashmaps Returing a vec is faster than updating a hashmap when the hashmap is not needed like in `hg files` which just list tracked files. Returning references avoid copying data when not needed improving performence for large repositories. Differential Revision: https://phab.mercurial-scm.org/D8861

repository: introduce constant for internal phase repo requirement and use it In future we will like to much cleaner logic around which requirement is for working copy and which can go in store. To start with that, we first need to de-clutter the requirement values spread around and replace them with constants. Differential Revision: https://phab.mercurial-scm.org/D8912

repository: introduce constant for sparse repo requirement and use it In future we will like to much cleaner logic around which requirement is for working copy and which can go in store. To start with that, we first need to de-clutter the requirement values spread around and replace them with constants. Differential Revision: https://phab.mercurial-scm.org/D8911

localrepo: refactor `.hg/requires` reading logic in separate function In an upcoming patch, we will be reusing this to read `.hg/store/requires`, so let's separate it in a different function before. Differential Revision: https://phab.mercurial-scm.org/D8910

localrepo: refactor logic to calculate sharedvfs in separate fn We will be reusing this in an upcoming patch, so better to refactor it into a separate function. Also the underlying handling deserves a function of it's own. Differential Revision: https://phab.mercurial-scm.org/D8909

keepalive: Do not append _rbuf if _raw_readinto exists (issue6356) The readline method append to the chunks the content of the _rbuf then there is a loop that call _raw_read which on Python3 call readinto. But the readinto version in mercurial append again the _rbuf content. So this creates the duplicate content. This does not happen in Python2 because _raw_read does not call readinto. Differential Revision: https://phab.mercurial-scm.org/D8859

store: refactor space delimited list to proper data structure There is no good reason why are having a space delimited list and then using `.split()` to get the actual list. Let's convert this into a proper collection. Differential Revision: https://phab.mercurial-scm.org/D8908