view tests/test-histedit-merge-tools.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 histedit extension: Merge tools
====================================

Initialization
---------------

  $ . "$TESTDIR/histedit-helpers.sh"

  $ cat >> $HGRCPATH <<EOF
  > [alias]
  > logt = log --template '{rev}:{node|short} {desc|firstline}\n'
  > [extensions]
  > histedit=
  > mockmakedate = $TESTDIR/mockmakedate.py
  > EOF

Merge conflict
--------------

  $ hg init r
  $ cd r
  $ cat >> .hg/hgrc <<EOF
  > [command-templates]
  > pre-merge-tool-output='pre-merge message for {node}\n'
  > EOF

  $ echo foo > file
  $ hg add file
  $ hg ci -m "First" -d "1 0"
  $ echo bar > file
  $ hg ci -m "Second" -d "2 0"

  $ hg logt --graph
  @  1:2aa920f62fb9 Second
  |
  o  0:7181f42b8fca First
  

Invert the order of the commits, but fail the merge.
  $ hg histedit --config ui.merge=false --commands - 2>&1 <<EOF | fixbundle
  > pick 2aa920f62fb9 Second
  > pick 7181f42b8fca First
  > EOF
  merging file
  pre-merge message for b90fa2e91a6d11013945a5f684be45b84a8ca6ec
  merging file failed!
  Fix up the change (pick 7181f42b8fca)
  (hg histedit --continue to resume)

  $ hg histedit --abort | fixbundle
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

Invert the order of the commits, and pretend the merge succeeded.
  $ hg histedit --config ui.merge=true --commands - 2>&1 <<EOF | fixbundle
  > pick 2aa920f62fb9 Second
  > pick 7181f42b8fca First
  > EOF
  merging file
  pre-merge message for b90fa2e91a6d11013945a5f684be45b84a8ca6ec
  7181f42b8fca: skipping changeset (no changes)
  $ hg histedit --abort
  abort: no histedit in progress
  [20]
  $ cd ..

Test legacy config name

  $ hg init r2
  $ cd r2
  $ echo foo > file
  $ hg add file
  $ hg ci -m "First"
  $ echo bar > file
  $ hg ci -m "Second"
  $ echo conflict > file
  $ hg co -m 0 --config ui.merge=false \
  > --config ui.pre-merge-tool-output-template='legacy config: {node}\n'
  merging file
  legacy config: 889c9c4d58bd4ce74815efd04a01e0f2bf6765a7
  merging file failed!
  0 files updated, 0 files merged, 0 files removed, 1 files unresolved
  use 'hg resolve' to retry unresolved file merges
  [1]