view tests/test-show-stack.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

  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > show =
  > EOF

  $ hg init repo0
  $ cd repo0

Empty repo / no checkout results in error

  $ hg show stack
  abort: stack view only available when there is a working directory
  [255]

Stack displays single draft changeset as root revision

  $ echo 0 > foo
  $ hg -q commit -A -m 'commit 0'
  $ hg show stack
    @  9f17 commit 0

Stack displays multiple draft changesets

  $ echo 1 > foo
  $ hg commit -m 'commit 1'
  $ echo 2 > foo
  $ hg commit -m 'commit 2'
  $ echo 3 > foo
  $ hg commit -m 'commit 3'
  $ echo 4 > foo
  $ hg commit -m 'commit 4'
  $ hg show stack
    @  2737 commit 4
    o  d1a6 commit 3
    o  128c commit 2
    o  181c commit 1
    o  9f17 commit 0

Public parent of draft base is displayed, separated from stack

  $ hg phase --public -r 0
  $ hg show stack
    @  2737 commit 4
    o  d1a6 commit 3
    o  128c commit 2
    o  181c commit 1
   /   (stack base)
  o  9f17 commit 0

  $ hg phase --public -r 1
  $ hg show stack
    @  2737 commit 4
    o  d1a6 commit 3
    o  128c commit 2
   /   (stack base)
  o  181c commit 1

Draft descendants are shown

  $ hg -q up 2
  $ hg show stack
    o  2737 commit 4
    o  d1a6 commit 3
    @  128c commit 2
   /   (stack base)
  o  181c commit 1

  $ hg -q up 3
  $ hg show stack
    o  2737 commit 4
    @  d1a6 commit 3
    o  128c commit 2
   /   (stack base)
  o  181c commit 1

working dir on public changeset should display special message

  $ hg -q up 1
  $ hg show stack
  (empty stack; working directory parent is a published changeset)

Branch point in descendants displayed at top of graph

  $ hg -q up 3
  $ echo b > foo
  $ hg commit -m 'commit 5 (new dag branch)'
  created new head
  $ hg -q up 2
  $ hg show stack
   \ /  (multiple children)
    |
    o  d1a6 commit 3
    @  128c commit 2
   /   (stack base)
  o  181c commit 1

  $ cd ..

Base is stopped at merges

  $ hg init merge-base
  $ cd merge-base
  $ echo 0 > foo
  $ hg -q commit -A -m initial
  $ echo h1 > foo
  $ hg commit -m 'head 1'
  $ hg -q up 0
  $ echo h2 > foo
  $ hg -q commit -m 'head 2'
  $ hg phase --public -r 0:tip
  $ hg -q up 1
  $ hg merge -t :local 2
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -m 'merge heads'

TODO doesn't yet handle case where wdir is a draft merge

  $ hg show stack
    @  8ee9 merge heads
   /   (stack base)
  o  5947 head 1

  $ echo d1 > foo
  $ hg commit -m 'draft 1'
  $ echo d2 > foo
  $ hg commit -m 'draft 2'

  $ hg show stack
    @  430d draft 2
    o  787b draft 1
   /   (stack base)
  o  8ee9 merge heads

  $ cd ..

Now move on to stacks when there are more commits after the base branchpoint

  $ hg init public-rebase
  $ cd public-rebase
  $ echo 0 > foo
  $ hg -q commit -A -m 'base'
  $ hg phase --public -r .
  $ echo d1 > foo
  $ hg commit -m 'draft 1'
  $ echo d2 > foo
  $ hg commit -m 'draft 2'
  $ hg -q up 0
  $ echo 1 > foo
  $ hg commit -m 'new 1'
  created new head
  $ echo 2 > foo
  $ hg commit -m 'new 2'
  $ hg -q up 2

Newer draft heads don't impact output

  $ hg show stack
    @  eaff draft 2
    o  2b21 draft 1
   /   (stack base)
  o  b66b base

Newer public heads are rendered

  $ hg phase --public -r '::tip'

  $ hg show stack
    o  baa4 new 2
   /    (2 commits ahead)
  :
  :    (stack head)
  : @  eaff draft 2
  : o  2b21 draft 1
  :/   (stack base)
  o  b66b base

If rebase is available, we show a hint how to rebase to that head

  $ hg --config extensions.rebase= show stack
    o  baa4 new 2
   /    (2 commits ahead; hg rebase --source 2b21 --dest baa4)
  :
  :    (stack head)
  : @  eaff draft 2
  : o  2b21 draft 1
  :/   (stack base)
  o  b66b base

Similar tests but for multiple heads

  $ hg -q up 0
  $ echo h2 > foo
  $ hg -q commit -m 'new head 2'
  $ hg phase --public -r .
  $ hg -q up 2

  $ hg show stack
    o  baa4 new 2
   /    (2 commits ahead)
  : o  9a84 new head 2
  :/    (1 commits ahead)
  :
  :    (stack head)
  : @  eaff draft 2
  : o  2b21 draft 1
  :/   (stack base)
  o  b66b base

  $ hg --config extensions.rebase= show stack
    o  baa4 new 2
   /    (2 commits ahead; hg rebase --source 2b21 --dest baa4)
  : o  9a84 new head 2
  :/    (1 commits ahead; hg rebase --source 2b21 --dest 9a84)
  :
  :    (stack head)
  : @  eaff draft 2
  : o  2b21 draft 1
  :/   (stack base)
  o  b66b base