filemerge: remove unused `orig` argument from tool functions Differential Revision: https://phab.mercurial-scm.org/D11878

filemerge: stop passing around 3 unused `None` values in `files` argument Since 67cfffbfb6a0 (filemerge: eliminate most uses of tempfiles, 2017-08-31), we have used only the last entry in the `files` tuple that gets passed around to various functions. That commit said "Emphasize that they're unused so we can more easily remove them later.". It's now "later". Differential Revision: https://phab.mercurial-scm.org/D11877

filemerge: rename backup variables from `back` to `backup` `backup` seems like an obviously clearer name for something containing something related to a backup. Differential Revision: https://phab.mercurial-scm.org/D11876

setup.py: fix some documentation typos Differential Revision: https://phab.mercurial-scm.org/D11944

dirstate-v2: Apply SECOND_AMBIGUOUS to directory mtimes too This would only be relevant in contrived scenarios such as a dirstate file being written with a libc that supports sub-second precision in mtimes, then transfered (at the filesystem level, not `hg clone`) to another system where libc *doesn’t* have sub-second precision and truncates the stored mtime of a directory to integer seconds. Differential Revision: https://phab.mercurial-scm.org/D11939

rank: actually persist revision's rank in changelog-v2 The changelog v2 format is now persisting whatever "rank" value is recorded. However keep in mind that for we do not record any value. Differential Revision: https://phab.mercurial-scm.org/D11937

rank: add a "rank" value to the revlog-entry tuple The rank of a revision is the size of sub-graph it defines as a head. In other words, the rank of X is the size of `ancestors(X)` (X included). This is a property that can help various algorithm and we intend to store it in changelog-v2. We start with adding this new information to the "entry tuple", with a default value. We will start to compute and persist the rank later. Differential Revision: https://phab.mercurial-scm.org/D11936

changelog-v2: fix an assertion error to display the right data We were checking on thing and displaying the other. Differential Revision: https://phab.mercurial-scm.org/D11935

changelog-v2: use helper constant in the code to pack/unpack entries This makes the code simpler to read and modify. This is probably less efficient, but we are talking about the Python implementation here, so performance is concerne secondary to readability. Differential Revision: https://phab.mercurial-scm.org/D11934

revlog: add some information about the revision we cannot find Parameter to Exception are good, use them. Differential Revision: https://phab.mercurial-scm.org/D11933