hgext/bookflow.py

bookflow: new extension for bookmark-based branching

This extension should be helpful for feature branches - based workflows.
At my company we first considered branches, but weren't sure about creating a lot of permanent objects.
We tried bookmarks, but found some scenarios to be difficult to control.

The main problem, was the active bookmark being moved on update.
Disabling that made everything a lot more predictable.

Bookmarks move on commit, and updating means switching between them.

The extension also implements a few minor features to better guide the workflow:
  - hg bookmark NAME can be ambiguous (create or move), unlike hg branch. The extension requires -rev to move.
  - require an active bookmark on commit.
  - some bookmarks can be protected (like @), useful for teams, that require code reviews.
  - block creation of new branches.

The initial implementation requires no changes in the core, but it does rely on some implementation details.
I thought it may be useful to discuss the functionality first, and then focus making the code more robust.

Differential Revision: https://phab.mercurial-scm.org/D4312

"""implements bookmark-based branching (EXPERIMENTAL)

 - Disables creation of new branches (config: enable_branches=False).
 - Requires an active bookmark on commit (config: require_bookmark=True).
 - Doesn't move the active bookmark on update, only on commit.
 - Requires '--rev' for moving an existing bookmark.
 - Protects special bookmarks (config: protect=@).

 flow related commands

    :hg book NAME: create a new bookmark
    :hg book NAME -r REV: move bookmark to revision (fast-forward)
    :hg up|co NAME: switch to bookmark
    :hg push -B .: push active bookmark
"""
from __future__ import absolute_import

from mercurial.i18n import _
from mercurial import (
    bookmarks,
    commands,
    error,
    extensions,
    registrar,
)

MY_NAME = 'bookflow'

configtable = {}
configitem = registrar.configitem(configtable)

configitem(MY_NAME, 'protect', ['@'])
configitem(MY_NAME, 'require-bookmark', True)
configitem(MY_NAME, 'enable-branches', False)

cmdtable = {}
command = registrar.command(cmdtable)

def commit_hook(ui, repo, **kwargs):
    active = repo._bookmarks.active
    if active:
        if active in ui.configlist(MY_NAME, 'protect'):
            raise error.Abort(
                _('cannot commit, bookmark {} is protected').format(active))
        if not cwd_at_bookmark(repo, active):
            raise error.Abort(
       _('cannot commit, working directory out of sync with active bookmark'),
                hint=_("run 'hg up {}'").format(active))
    elif ui.configbool(MY_NAME, 'require-bookmark', True):
        raise error.Abort(_('cannot commit without an active bookmark'))
    return 0

def bookmarks_update(orig, repo, parents, node):
    if len(parents) == 2:
        # called during commit
        return orig(repo, parents, node)
    else:
        # called during update
        return False

def bookmarks_addbookmarks(
        orig, repo, tr, names, rev=None, force=False, inactive=False):
    if not rev:
        marks = repo._bookmarks
        for name in names:
            if name in marks:
                raise error.Abort(
                    _("bookmark {} already exists, to move use the --rev option"
                    ).format(name))
    return orig(repo, tr, names, rev, force, inactive)

def commands_commit(orig, ui, repo, *args, **opts):
    commit_hook(ui, repo)
    return orig(ui, repo, *args, **opts)

def commands_pull(orig, ui, repo, *args, **opts):
    rc = orig(ui, repo, *args, **opts)
    active = repo._bookmarks.active
    if active and not cwd_at_bookmark(repo, active):
        ui.warn(_(
            "working directory out of sync with active bookmark, run 'hg up {}'"
        ).format(active))
    return rc

def commands_branch(orig, ui, repo, label=None, **opts):
    if label and not opts.get(r'clean') and not opts.get(r'rev'):
        raise error.Abort(
         _("creating named branches is disabled and you should use bookmarks"),
            hint="see 'hg help bookflow'")
    return orig(ui, repo, label, **opts)

def cwd_at_bookmark(repo, mark):
    mark_id = repo._bookmarks[mark]
    cur_id = repo.lookup('.')
    return cur_id == mark_id

def uisetup(ui):
    extensions.wrapfunction(bookmarks, 'update', bookmarks_update)
    extensions.wrapfunction(bookmarks, 'addbookmarks', bookmarks_addbookmarks)
    extensions.wrapcommand(commands.table, 'commit', commands_commit)
    extensions.wrapcommand(commands.table, 'pull', commands_pull)
    if not ui.configbool(MY_NAME, 'enable-branches'):
        extensions.wrapcommand(commands.table, 'branch', commands_branch)