Log Message:
py-mercurial: update to 5.1.

This is an overview of the 5.1 release.

1. New Features

    New config commands.commit.post-status shows status after
    successful commit.

    hg root now has templating support, including support for
    showing where a repo share's source is. See hg help -v root
    for details.

    New --force-close-branch flag for hg commit to forcibly close
    branch from a non-head changeset.

    The curses-based interface for commands like hg commit -i now
    supports a range-select mechanism. Select the first line using
    space like before, navigate to the last line, and press X
    (capital x) to set all items in the range at once. Lowercase
    x has been added as a synonym for space to help reinforce the
    mechanism, and pressing enter/return continues to be a synonym
    for "toggle the current line and move down to the next item in
    this section."

2. New Experimental Features

    New config experimental.log.topo makes hg log -G use topological
    sorting. This is especially useful for aliases since it lets
    the alias accept an -r option while still using topological
    sorting with or without the -r (unlike if you use the `sort(...,
    topo)` revset).

3. Bug Fixes

    issue4292: "hg log and {files} {file_adds} {file_mods} {file_dels}
    in template show wrong files on merged revision". See details
    in "Backwards Compatibility Changes".

4. Backwards Compatibility Changes

    Removed (experimental) support for log graph lines mixing
    parent/grandparent styles. Setting e.g. experimental.graphstyle.parent
    = ! and experimental.graphstyle.grandparent = 3. would use !
    for the first three lines of the graph and then .. This is no
    longer supported.

    If ui.origbackuppath had been (incorrectly) configured to point
    to a file, we will now replace that file by a directory and
    put backups in that directory. This is similar to how we would
    previously replace files *in* the configured directory by
    subdirectories.

    Template keyword {file_mods}, {file_adds}, and {file_dels} have
    changed behavior on merge commits. They used to be relative to
    the first parent, but they now consider both parents. {file_adds}
    shows files that exists in the commit but did not exist in
    either parent. {file_dels} shows files that do not exist in
    the commit but existed in either parent. {file_mods} show the
    remaining files from {files} that were not in the other two
    sets.

5. Internal API Changes

    Matchers are no longer iterable. Use match.files() instead.

    match.visitdir() and match.visitchildrenset() now expect the
    empty string instead of '.' to indicate the root directory.

    util.dirs() and util.finddirs() now include an entry for the
    root directory (empty string).

    shelve is no longer an extension now. it will be turned on by
    default.

    New API to manage unfinished operations: Earlier there were
    distinct APIs which dealt with unfinished states and separate
    lists maintaining them that are cmdutil.afterresolvestates,
    cmdutil.unfinishedstates and cmdutil.STATES. Now these have
    been unified to a single API which handles the various states
    and their utilities. This API has been added to state.py. Now
    instead of adding to these 3 lists independently a state for
    a new operation can be registered using addunfinished() in
    state module.

    cmdutil.checkunfinished() now includes detection for merge too.
    merge abort has been disallowed in case an operation of higher
    precedence is in progress to avoid cases of partial abort of
    operations.

    We used to automatically attempt to make extensions compatible
    with Python 3 (by translating their source code while loading
    it). We no longer do that.