view tests/test-contrib.t @ 39496:2f9f7889549b

snapshot: introduce an intermediate `_refinedgroups` generator

This method will be used to improve the search for a good snapshot base. To
keep things simpler, we introduce the necessary function before doing any
delta base logic change. The next handful of commits will focus on refactoring
the code to let that new logic land as clearly as possible.

# General Idea

Right now, the search for a good delta base stop whenever we found a good one.
However, when using sparse-revlog, we should probably try a bit harder.

We do significant effort to increase delta re-use by jumping on "unrelated"
delta chains that provide better results. Moving to another chain for a better
result is good, but we have no guarantee we jump at a reasonable point in that
new chain. When we consider over the chains related to the parents, we start
from the higher-level snapshots. This is a way to consider the snapshot closer
to the current revision that has the best chance to produce a small delta. We
do benefit from this walk order when jumping to a better "unrelated" stack.

To counter-balance this, we'll introduce a way to "refine" the result. After a
good delta have been found, we'll keep searching for a better delta, using the
current best one as a starting point.

# Target Setup

The `finddeltainfo` method is responsible for the general search for a good
delta. It requests candidates base from `_candidategroups` and decides which
one are usable.

The `_candidategroups` generator act as a top-level filter, it does not care
about how we pick candidates, it just does basic filtering, excluding
revisions that have been tested already or that are an obvious misfit.

The `_rawgroups` generator is the one with the actual ancestors walking logic,
It does not care about what would do a good delta and what was already tested,
it just issues the initial candidates.

We introduce a new `_refinedgroup` function to bridge the gap between
`_candidategroups` and `_rawgroups`. It delegates the initial iteration logic
and then performing relevant refining of the valid base once found. (This
logic is yet to be added to function)

All these logics are fairly independent and easier to understand when standing
alone, not mixed with each other. It also makes it easy to test and try
different approaches for one of those four layers without affecting the other
ones.

# Technical details

To communicate `finddeltainfo` choice of "current best delta base" to the
`_refinegroup` logic, we plan to use python co-routine feature. The
`_candidategroups` and `_refinegroup` generators will become co-routine. This
will allow `_refinegroup` to detect when a good delta have been found and
triggers various refining steps.

For now, `_candidategroups` will just pass the value down the stack.

After poking at various option, the co-routine appears the best to keep each
layers focus on its duty, without the need to spread implementation details
across layers.

Set vars:

  $ CONTRIBDIR="$TESTDIR/../contrib"

Test simplemerge command:

  $ cp "$CONTRIBDIR/simplemerge" .
  $ echo base > base
  $ echo local > local
  $ cat base >> local
  $ cp local orig
  $ cat base > other
  $ echo other >> other

changing local directly

  $ $PYTHON simplemerge local base other && echo "merge succeeded"
  merge succeeded
  $ cat local
  local
  base
  other
  $ cp orig local

printing to stdout

  $ $PYTHON simplemerge -p local base other
  local
  base
  other

local:

  $ cat local
  local
  base

conflicts

  $ cp base conflict-local
  $ cp other conflict-other
  $ echo not other >> conflict-local
  $ echo end >> conflict-local
  $ echo end >> conflict-other

  $ $PYTHON simplemerge -p conflict-local base conflict-other
  base
  <<<<<<< conflict-local
  not other
  =======
  other
  >>>>>>> conflict-other
  end
  [1]

1 label

  $ $PYTHON simplemerge -p -L foo conflict-local base conflict-other
  base
  <<<<<<< foo
  not other
  =======
  other
  >>>>>>> conflict-other
  end
  [1]

2 labels

  $ $PYTHON simplemerge -p -L foo -L bar conflict-local base conflict-other
  base
  <<<<<<< foo
  not other
  =======
  other
  >>>>>>> bar
  end
  [1]

3 labels

  $ $PYTHON simplemerge -p -L foo -L bar -L base conflict-local base conflict-other
  base
  <<<<<<< foo
  not other
  end
  ||||||| base
  =======
  other
  end
  >>>>>>> bar
  [1]

too many labels

  $ $PYTHON simplemerge -p -L foo -L bar -L baz -L buz conflict-local base conflict-other
  abort: can only specify three labels.
  [255]

binary file

  $ $PYTHON -c "f = open('binary-local', 'w'); f.write('\x00'); f.close()"
  $ cat orig >> binary-local
  $ $PYTHON simplemerge -p binary-local base other
  warning: binary-local looks like a binary file.
  [1]

binary file --text

  $ $PYTHON simplemerge -a -p binary-local base other 2>&1
  warning: binary-local looks like a binary file.
  \x00local (esc)
  base
  other

help

  $ $PYTHON simplemerge --help
  simplemerge [OPTS] LOCAL BASE OTHER
  
      Simple three-way file merge utility with a minimal feature set.
  
      Apply to LOCAL the changes necessary to go from BASE to OTHER.
  
      By default, LOCAL is overwritten with the results of this operation.
  
  options:
   -L --label       labels to use on conflict markers
   -a --text        treat all files as text
   -p --print       print results instead of overwriting LOCAL
      --no-minimal  no effect (DEPRECATED)
   -h --help        display help and exit
   -q --quiet       suppress output

wrong number of arguments

  $ $PYTHON simplemerge
  simplemerge: wrong number of arguments
  simplemerge [OPTS] LOCAL BASE OTHER
  
      Simple three-way file merge utility with a minimal feature set.
  
      Apply to LOCAL the changes necessary to go from BASE to OTHER.
  
      By default, LOCAL is overwritten with the results of this operation.
  
  options:
   -L --label       labels to use on conflict markers
   -a --text        treat all files as text
   -p --print       print results instead of overwriting LOCAL
      --no-minimal  no effect (DEPRECATED)
   -h --help        display help and exit
   -q --quiet       suppress output
  [1]

bad option

  $ $PYTHON simplemerge --foo -p local base other
  simplemerge: option --foo not recognized
  simplemerge [OPTS] LOCAL BASE OTHER
  
      Simple three-way file merge utility with a minimal feature set.
  
      Apply to LOCAL the changes necessary to go from BASE to OTHER.
  
      By default, LOCAL is overwritten with the results of this operation.
  
  options:
   -L --label       labels to use on conflict markers
   -a --text        treat all files as text
   -p --print       print results instead of overwriting LOCAL
      --no-minimal  no effect (DEPRECATED)
   -h --help        display help and exit
   -q --quiet       suppress output
  [1]