[PATCH V4] copy: add flag for disabling copy tracing

[Martin von Zweigbergk]

On Tue, Apr 14, 2015 at 6:56 AM Durham Goode <durham at fb.com> wrote:

> # HG changeset patch
> # User Durham Goode <durham at fb.com>
> # Date 1422386787 28800
> #      Tue Jan 27 11:26:27 2015 -0800
> # Node ID 5a39559f0caa07ca1a44ee67f7f917138b54198f
> # Parent  52ff737c63d2b2cb41185549aa9c35bc47317032
> copy: add flag for disabling copy tracing
>
> Copy tracing can be up to 80% of rebase time when rebasing stacks
> of commits in large repos (hundreds of thousands of files).
>

Does most of that come from copies.mergecopies() or
copies.duplicatecopies()? I saw 10% in mergecopies() and 18% in
duplicatecopies(), but that was in a smaller repo and rebasing across a
smaller distance.


> This provides the option of turning off the majority of copy tracing. It
> does not turn off _forwardcopies() since that is used to carry copy
> information inside a commit across a rebase.
>

How is this different from merge.followcopies? (I'm not saying it's not,
I'm just asking.) IIUC, merge.followcopies=False still calls
duplicatecopies(), which is supposed to "reproduce copies from fromrev to
rev in the dirstate". Does your new option turn off make us not duplicate
some copies that would have been found with merge.followcopies=False?


>
> This will affect the situation where a user edits a file, then rebases on
> top of
> commits that have moved that file. The move will not be detected and the
> user
> will have to manually resolve the issue (possibly by redoing the rebase
> with
> this flag off).
>
> This takes rebasing a 3 commit stack that's a couple weeks old from 65s to
> 12s.
>
> diff --git a/mercurial/copies.py b/mercurial/copies.py
> --- a/mercurial/copies.py
> +++ b/mercurial/copies.py
> @@ -186,6 +186,9 @@ def _forwardcopies(a, b):
>      return cm
>
>  def _backwardrenames(a, b):
> +    if a._repo.ui.configbool('experimental', 'disablecopytrace'):
> +        return {}
> +
>      # Even though we're not taking copies into account, 1:n rename
> situations
>      # can still exist (e.g. hg cp a b; hg mv a c). In those cases we
>      # arbitrarily pick one of the renames.
> @@ -258,6 +261,13 @@ def mergecopies(repo, c1, c2, ca):
>      if c2.node() is None and c1.node() == repo.dirstate.p1():
>          return repo.dirstate.copies(), {}, {}, {}
>
> +    if repo.ui.configbool('experimental', 'disablecopytrace'):
> +        # If we're just tracking against the parent, do a simple check.
> +        # This is necessary to ensure copies survive rebasing.
> +        if ca in c2.parents():
> +            return pathcopies(ca, c2), {}, {}, {}
> +        return {}, {}, {}, {}
> +
>      limit = _findlimit(repo, c1.rev(), c2.rev())
>      if limit is None:
>          # no common ancestor, no copies
> @@ -506,7 +516,8 @@ def duplicatecopies(repo, rev, fromrev,
>      copies between fromrev and rev.
>      '''
>      exclude = {}
> -    if skiprev is not None:
> +    if (skiprev is not None and
> +        not repo.ui.configbool('experimental', 'disablecopytrace')):
>          exclude = pathcopies(repo[fromrev], repo[skiprev])
>      for dst, src in pathcopies(repo[fromrev], repo[rev]).iteritems():
>          # copies.pathcopies returns backward renames, so dst might not
> diff --git a/tests/test-copy-move-merge.t b/tests/test-copy-move-merge.t
> --- a/tests/test-copy-move-merge.t
> +++ b/tests/test-copy-move-merge.t
> @@ -61,4 +61,73 @@ file c
>    1
>    2
>
> +Test disabling copy tracing
> +
> +- first verify copy metadata was kept
> +
> +  $ hg up -qC 2
> +  $ hg rebase --keep -d 1 -b 2 --config extensions.rebase=
> +  rebasing 2:add3f11052fa "other" (tip)
> +  merging b and a to b
> +  merging c and a to c
> +
> +  $ cat b
> +  0
> +  1
> +  2
> +
> +- next verify copy metadata is lost when disabled
> +
> +  $ hg strip -r . --config extensions.strip=
> +  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
> +  saved backup bundle to
> $TESTTMP/t/.hg/strip-backup/550bd84c0cd3-fc575957-backup.hg (glob)
> +  $ hg up -qC 2
> +  $ hg rebase --keep -d 1 -b 2 --config extensions.rebase= --config
> experimental.disablecopytrace=True
> +  rebasing 2:add3f11052fa "other" (tip)
> +  remote changed a which local deleted
> +  use (c)hanged version or leave (d)eleted? c
> +
> +  $ cat b
> +  1
> +  2
> +
>    $ cd ..
> +
> +Verify disabling copy tracing still keeps copies from rebase source
> +
> +  $ hg init copydisable
> +  $ cd copydisable
> +  $ touch a
> +  $ hg ci -Aqm a
> +  $ touch b
> +  $ touch c
> +  $ hg ci -Aqm b
> +  $ hg cp b x
> +  $ hg cp c y
> +  $ echo x >> x
> +  $ hg ci -qm xy
> +  $ hg up -q 1
> +  $ hg cp b x
> +  $ touch z
> +  $ hg ci -Aqm xz
> +  $ hg log -G -T '{rev} {desc}\n'
> +  @  3 xz
> +  |
> +  | o  2 xy
> +  |/
> +  o  1 b
> +  |
> +  o  0 a
> +
> +  $ hg rebase -d . -b 2 --config extensions.rebase= --config
> experimental.disablecopytrace=True
> +  rebasing 2:002ca7a9f426 "xy"
> +  merging x
> +  saved backup bundle to
> $TESTTMP/copydisable/.hg/strip-backup/002ca7a9f426-19f9ad1e-backup.hg (glob)
> +  $ hg up -q 3
> +  $ hg log -f x -T '{rev} {desc}\n'
> +  3 xy
> +  2 xz
> +  1 b
> +  $ hg log -f y -T '{rev} {desc}\n'
> +  3 xy
> +  1 b
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