fastannotate: implement the command

Summary:
This diff adds the `fastannotate` command, which puts all components
(formatter, annotatecontext - linelog, revmap) together.

Note that `fastannotate.mainbranch` needs to be carefully chosen to avoid
rebuilds. If `mainbranch` moves backwards, the `fastannotate` command
can fail because it could not move linelog backwards and thus cannot
update linelog incrementally.

Test Plan: Code Review. The `.t` file is coming in the next diff.

Reviewers: #sourcecontrol, stash

Reviewed By: stash

Subscribers: stash, mjpieters

Differential Revision: https://phabricator.intern.facebook.com/D3836670

Signature: t1:3836670:1474016576:b323b62db3bfd69bff88f6911abbe26075734737

fastannotate/__init__.py

@@ -0,0 +1,43 @@
+# Copyright 2016-present Facebook. All Rights Reserved.
+#
+# fastannotate: faster annotate implementation using linelog
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+
+"""yet another annotate implementation that might be faster
+
+The fastannotate extension provides a 'fastannotate' command that makes
+use of the linelog data structure as a cache layer and is expected to
+be faster than the vanilla 'annotate' if the cache is present.
+
+::
+
+    [fastannotate]
+    # specify the main branch head. the internal linelog will only contain
+    # the linear (ignoring p2) "mainbranch". since linelog cannot move
+    # backwards without a rebuild, this should be something that always moves
+    # forward, usually it is "master" or "@".
+    mainbranch = master
+    # use unfiltered repo for better performance
+    unfilteredrepo = True
+"""
+
+from __future__ import absolute_import
+
+from fastannotate import commands
+
+from mercurial import (
+    cmdutil,
+)
+
+testedwith = 'internal'
+
+cmdtable = {}
+command = cmdutil.command(cmdtable)
+
+command('^fastannotate|fastblame|fa',
+        **commands.fastannotatecommandargs
+       )(commands.fastannotate)
+

fastannotate/commands.py

@@ -0,0 +1,118 @@
+# Copyright 2016-present Facebook. All Rights Reserved.
+#
+# commands: fastannotate commands
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+from __future__ import absolute_import
+
+from fastannotate import (
+    context as facontext,
+    error as faerror,
+    formatter as faformatter,
+)
+
+from mercurial import (
+    commands,
+    error,
+    scmutil,
+)
+
+from mercurial.i18n import _
+
+fastannotatecommandargs = {
+    'options': [
+        ('r', 'rev', '.', _('annotate the specified revision'), _('REV')),
+        ('u', 'user', None, _('list the author (long with -v)')),
+        ('f', 'file', None, _('list the filename')),
+        ('d', 'date', None, _('list the date (short with -q)')),
+        ('n', 'number', None, _('list the revision number (default)')),
+        ('c', 'changeset', None, _('list the changeset')),
+        ('l', 'line-number', None, _('show line number at the first '
+                                     'appearance')),
+        ('h', 'no-content', None, _('do not show file content')),
+        ('', 'no-follow', None, _("don't follow copies and renames")),
+        ('', 'linear', None, _('enforce linear history, ignore second parent '
+                               'of merges (faster)')),
+        ('', 'long-hash', None, _('show long changeset hash (EXPERIMENTAL)')),
+        ('', 'rebuild', None, _('rebuild cache even if it exists '
+                                '(EXPERIMENTAL)')),
+    ] + commands.walkopts,
+    'synopsis': _('[-r REV] [-f] [-a] [-u] [-d] [-n] [-c] [-l] FILE...'),
+    'inferrepo': True,
+}
+
+def fastannotate(ui, repo, *pats, **opts):
+    """show changeset information by line for each file
+
+    List changes in files, showing the revision id responsible for each line.
+
+    This command is useful for discovering when a change was made and by whom.
+
+    If you include --file, --user, or --date, the revision number is suppressed
+    unless you also include --number.
+
+    This command uses an implementation different from the vanilla annotate
+    command, which may produce slightly different (while still reasonable)
+    output for some cases.
+
+    For the best performance, use -c, -l, avoid -u, -d, -n. Use --linear
+    and --no-content to make it even faster.
+
+    Returns 0 on success.
+    """
+    if not pats:
+        raise error.Abort(_('at least one filename or pattern is required'))
+
+    # performance hack: filtered repo can be slow. unfilter by default.
+    if ui.configbool('fastannotate', 'unfilteredrepo', True):
+        repo = repo.unfiltered()
+
+    rev = opts.get('rev', '.')
+    rebuild = opts.get('rebuild', False)
+
+    ctx = scmutil.revsingle(repo, rev)
+    m = scmutil.match(ctx, pats, opts)
+
+    aopts = facontext.annotateopts(
+        followmerge=not opts.get('linear', False),
+        followrename=not opts.get('no_follow', False))
+
+    if not any(opts.get(s)
+               for s in ['user', 'date', 'file', 'number', 'changeset']):
+        # default 'number' for compatibility. but fastannotate is more
+        # efficient with "changeset", "line-number" and "no-content".
+        for name in ui.configlist('fastannotate', 'defaultformat', ['number']):
+            opts[name] = True
+
+    formatter = faformatter.defaultformatter(ui, repo, opts)
+    showlines = not bool(opts.get('no_content'))
+    showpath = opts.get('file', False)
+
+    # find the head of the main (master) branch
+    masterrev = ui.config('fastannotate', 'mainbranch')
+    if masterrev:
+        master = lambda: scmutil.revsingle(repo, masterrev).rev()
+    else:
+        master = rev
+
+    for path in ctx.walk(m):
+        result = lines = None
+        while True:
+            try:
+                with facontext.annotatecontext(repo, path, aopts, rebuild) as a:
+                    result = a.annotate(rev, master=master, showpath=showpath,
+                                        showlines=showlines)
+                break
+            except faerror.CannotReuseError: # happens if master moves backwards
+                if rebuild: # give up since we have tried rebuild alreadyraise
+                    raise
+                else: # try a second time rebuilding the cache (slow)
+                    rebuild = True
+                    continue
+
+        if showlines:
+            result, lines = result
+
+        formatter.write(result, lines)