tests/test-fix-pickle.t

dirstate-tree: Make `DirstateMap` borrow from a bytes buffer

… that has the contents of the `.hg/dirstate` file.
This only applies to the tree-based flavor of `DirstateMap`.

For now only the entire `&[u8]` slice is stored, so this is not useful yet.

Adding a lifetime parameter to the `DirstateMap` struct (in hg-core) makes
Python bindings non-trivial because we keep that struct in a Python object
that has a dynamic lifetime tied to Python’s reference-counting and GC.
As long as we keep the `PyBytes` that owns the borrowed bytes buffer next to
the borrowing struct, the buffer will live long enough for the borrows to stay
valid. However this relationship cannot be expressed in safe Rust code in a
way that would statisfy they borrow-checker. We use `unsafe` code to erase
that lifetime parameter, and encapsulate it in a safe abstraction similar to
the owning-ref crate: https://docs.rs/owning_ref/

Differential Revision: https://phab.mercurial-scm.org/D10557

A script that implements uppercasing all letters in a file.

  $ UPPERCASEPY="$TESTTMP/uppercase.py"
  $ cat > $UPPERCASEPY <<EOF
  > import sys
  > from mercurial.utils.procutil import setbinary
  > setbinary(sys.stdin)
  > setbinary(sys.stdout)
  > sys.stdout.write(sys.stdin.read().upper())
  > EOF
  $ TESTLINES="foo\nbar\nbaz\n"
  $ printf $TESTLINES | "$PYTHON" $UPPERCASEPY
  FOO
  BAR
  BAZ

This file attempts to test our workarounds for pickle's lack of
support for short reads.

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > fix =
  > [fix]
  > uppercase-whole-file:command="$PYTHON" $UPPERCASEPY
  > uppercase-whole-file:pattern=set:**
  > EOF

  $ hg init repo
  $ cd repo

# Create a file that's large enough that it seems to not fit in
# pickle's buffer, making it use the code path that expects our
# _blockingreader's read() method to return bytes.
  $ echo "some stuff" > file
  $ for i in $($TESTDIR/seq.py 13); do
  >   cat file file > tmp
  >   mv -f tmp file
  > done
  $ hg commit -Am "add large file"
  adding file

Check that we don't get a crash

  $ hg fix -r .
  saved backup bundle to $TESTTMP/repo/.hg/strip-backup/*-fix.hg (glob)