revlog: separate diff computation from the collection of other info

revlog: introduce 'deltainfo' to distinguish from 'delta' A 'delta' is a binary diff between two revisions, as returned by revdiff. A 'deltainfo' is an object storing information about a delta, including the 'delta' itself. Formerly, it was stored in a 7-position tuple, which was less readable.

revlog: extract 'builddelta' closure function from _addrevision

revlog: extract 'buildtext' closure function from _addrevision

revlog: choose between ifh and dfh once for all

revlog: refactor out the selection of candidate revisions The new function will be useful to retrieve all the revisions which will be needed to determine the best delta, and parallelize the computation of the necessary diffs.

py3: use email.parser module to parse email messages Before this patch we use email.Parser.Parser() from the email module which is not available on Python 3. On Python 2: >>> import email >>> import email.parser as emailparser >>> email.Parser.Parser is emailparser.Parser True

rust: convert Unix path to CString transparently On Unix, path is just a sequence of bytes. We shouldn't convert it to UTF-8 string.

rust: extract function to convert Path to platform CString It can be better on Unix.

pylint: add a check for multiple statement on a single line Now that they are all cleaned up, we can install a check so that no new occurrence appears. Differential Revision: https://phab.mercurial-scm.org/D1834