view tests/test-copy-move-merge.t @ 49000:dd6b67d5c256 stable

rust: fix unsound `OwningDirstateMap`

As per the previous patch, `OwningDirstateMap` is unsound. Self-referential
structs are difficult to implement correctly in Rust since the compiler is
free to move structs around as much as it wants to. They are also very rarely
needed in practice, so the state-of-the-art on how they should be done within
the Rust rules is still a bit new.

The crate `ouroboros` is an attempt at providing a safe way (in the Rust sense)
of declaring self-referential structs. It is getting a lot attention and was
improved very quickly when soundness issues were found in the past: rather than
relying on our own (limited) review circle, we might as well use the de-facto
common crate to fix this problem. This will give us a much better chance of
finding issues should any new ones be discovered as well as the benefit of
fewer `unsafe` APIs of our own.

I was starting to think about how I would present a safe API to the old struct
but soon realized that the callback-based approach was already done in
`ouroboros`, along with a lot more care towards refusing incorrect structs.

In short: we don't return a mutable reference to the `DirstateMap` anymore, we
expect users of its API to pass a `FnOnce` that takes the map as an argument.
This allows our `OwningDirstateMap` to control the input and output lifetimes
of the code that modifies it to prevent such issues.

Changing to `ouroboros` meant changing every API with it, but it is relatively
low churn in the end. It correctly identified the example buggy modification of
`copy_map_insert` outlined in the previous patch as violating the borrow rules.

Differential Revision: https://phab.mercurial-scm.org/D12429

Test for the full copytracing algorithm
=======================================


Initial Setup
=============

use git diff to see rename

  $ cat << EOF >> $HGRCPATH
  > [diff]
  > git=yes
  > EOF

Setup an history where one side copy and rename a file (and update it) while the other side update it.

  $ hg init t
  $ cd t

  $ echo 1 > a
  $ hg ci -qAm "first"

  $ hg cp a b
  $ hg mv a c
  $ echo 2 >> b
  $ echo 2 >> c

  $ hg ci -qAm "second"

  $ hg co -C 0
  1 files updated, 0 files merged, 2 files removed, 0 files unresolved

  $ echo 0 > a
  $ echo 1 >> a

  $ hg ci -qAm "other"

  $ hg log -G --patch
  @  changeset:   2:add3f11052fa
  |  tag:         tip
  |  parent:      0:b8bf91eeebbc
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     other
  |
  |  diff --git a/a b/a
  |  --- a/a
  |  +++ b/a
  |  @@ -1,1 +1,2 @@
  |  +0
  |   1
  |
  | o  changeset:   1:17c05bb7fcb6
  |/   user:        test
  |    date:        Thu Jan 01 00:00:00 1970 +0000
  |    summary:     second
  |
  |    diff --git a/a b/b
  |    rename from a
  |    rename to b
  |    --- a/a
  |    +++ b/b
  |    @@ -1,1 +1,2 @@
  |     1
  |    +2
  |    diff --git a/a b/c
  |    copy from a
  |    copy to c
  |    --- a/a
  |    +++ b/c
  |    @@ -1,1 +1,2 @@
  |     1
  |    +2
  |
  o  changeset:   0:b8bf91eeebbc
     user:        test
     date:        Thu Jan 01 00:00:00 1970 +0000
     summary:     first
  
     diff --git a/a b/a
     new file mode 100644
     --- /dev/null
     +++ b/a
     @@ -0,0 +1,1 @@
     +1
  

Test Simple Merge
=================

  $ hg merge --debug
    unmatched files in other:
     b
     c
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     on remote side:
      src: 'a' -> dst: 'b' *
      src: 'a' -> dst: 'c' *
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: b8bf91eeebbc, local: add3f11052fa+, remote: 17c05bb7fcb6
  starting 4 threads for background file closing (?)
   preserving a for resolve of b
   preserving a for resolve of c
  removing a
   b: remote moved from a -> m
  picked tool ':merge' for b (binary False symlink False changedelete False)
  merging a and b to b
  my b@add3f11052fa+ other b@17c05bb7fcb6 ancestor a@b8bf91eeebbc
   premerge successful
   c: remote moved from a -> m
  picked tool ':merge' for c (binary False symlink False changedelete False)
  merging a and c to c
  my c@add3f11052fa+ other c@17c05bb7fcb6 ancestor a@b8bf91eeebbc
   premerge successful
  0 files updated, 2 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

file b
  $ cat b
  0
  1
  2

file c
  $ cat c
  0
  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 tip "other"
  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
  $ hg up -qC 2
  $ hg rebase --keep -d 1 -b 2 --config extensions.rebase= --config experimental.copytrace=off --config ui.interactive=True << EOF
  > c
  > EOF
  rebasing 2:add3f11052fa tip "other"
  file 'a' was deleted in local [dest] but was modified in other [source].
  You can use (c)hanged version, leave (d)eleted, or leave (u)nresolved.
  What do you want to do? 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 'add a'
  $ touch b
  $ hg ci -Aqm 'add b, c'
  $ hg cp b x
  $ echo x >> x
  $ hg ci -qm 'copy b->x'
  $ hg up -q 1
  $ touch z
  $ hg ci -Aqm 'add z'
  $ hg log -G -T '{rev} {desc}\n'
  @  3 add z
  |
  | o  2 copy b->x
  |/
  o  1 add b, c
  |
  o  0 add a
  
  $ hg rebase -d . -b 2 --config extensions.rebase= --config experimental.copytrace=off
  rebasing 2:6adcf8c12e7d "copy b->x"
  saved backup bundle to $TESTTMP/copydisable/.hg/strip-backup/6adcf8c12e7d-ce4b3e75-rebase.hg
  $ hg up -q 3
  $ hg log -f x -T '{rev} {desc}\n'
  3 copy b->x
  1 add b, c

  $ cd ../


test storage preservation
-------------------------

Verify rebase do not discard recorded copies data when copy tracing usage is
disabled.

Setup

  $ hg init copydisable3
  $ cd copydisable3
  $ touch a
  $ hg ci -Aqm 'add a'
  $ hg cp a b
  $ hg ci -Aqm 'copy a->b'
  $ hg mv b c
  $ hg ci -Aqm 'move b->c'
  $ hg up -q 0
  $ hg cp a b
  $ echo b >> b
  $ hg ci -Aqm 'copy a->b (2)'
  $ hg log -G -T '{rev} {desc}\n'
  @  3 copy a->b (2)
  |
  | o  2 move b->c
  | |
  | o  1 copy a->b
  |/
  o  0 add a
  

Actual Test

A file is copied on one side and has been moved twice on the other side. the
file is copied from `0:a`, so the file history of the `3:b` should trace directly to `0:a`.

  $ hg rebase -d 2 -s 3 --config extensions.rebase= --config experimental.copytrace=off
  rebasing 3:47e1a9e6273b tip "copy a->b (2)"
  saved backup bundle to $TESTTMP/copydisable3/.hg/strip-backup/47e1a9e6273b-2d099c59-rebase.hg

  $ hg log -G -f b
  @  changeset:   3:76024fb4b05b
  :  tag:         tip
  :  user:        test
  :  date:        Thu Jan 01 00:00:00 1970 +0000
  :  summary:     copy a->b (2)
  :
  o  changeset:   0:ac82d8b1f7c4
     user:        test
     date:        Thu Jan 01 00:00:00 1970 +0000
     summary:     add a