view tests/test-simple-update.t @ 46667:93e9f448273c

rhg: Add support for automatic fallback to Python

`rhg` is a command-line application that can do a small subset of what
`hg` can. It is written entirely in Rust, which avoids the cost of starting
a Python interpreter and importing many Python modules.
In a script that runs many `hg` commands, this cost can add up.

However making users decide when to use `rhg` instead of `hg` is
not practical as we want the subset of supported functionality
to grow over time.

Instead we introduce "fallback" behavior where, when `rhg` encounters
something (a sub-command, a repository format, …) that is not implemented
in Rust-only, it does nothing but silently start a subprocess of
Python-based `hg` running the same command.
That way `rhg` becomes a drop-in replacement for `hg` that sometimes
goes faster. Whether Python is used should be an implementation detail
not apparent to users (other than through speed).

A new `fallback` value is added to the previously introduced
`rhg.on-unsupported` configuration key. When in this mode, the new
`rhg.fallback-executable` config is determine what command to use
to run a Python-based `hg`.

The previous `rhg.on-unsupported = abort-silent` configuration was designed
to let a wrapper script call `rhg` and then fall back to `hg` based on the
exit code. This is still available, but having fallback behavior built-in
in rhg might be easier for users instead of leaving that script "as an
exercise for the reader".

Using a subprocess like this is not idea, especially when `rhg` is to be
installed in `$PATH` as `hg`, since the other `hg.py` executable needs
to still be available… somewhere. Eventually this could be replaced
by using PyOxidizer to a have a single executable that embeds a Python
interpreter, but only starts it when needed.

Differential Revision: https://phab.mercurial-scm.org/D10093

  $ hg init test
  $ cd test
  $ echo foo>foo
  $ hg addremove
  adding foo
  $ hg commit -m "1"

  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 1 changesets with 1 changes to 1 files

  $ hg clone . ../branch
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd ../branch
  $ hg co
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo bar>>foo
  $ hg commit -m "2" -d '1 0'

  $ cd ../test

  $ hg pull ../branch
  pulling from ../branch
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets 84b9316f7b31
  1 local changesets published
  (run 'hg update' to get a working copy)

  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 2 changesets with 2 changes to 1 files

  $ hg co
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cat foo
  foo
  bar

  $ hg manifest --debug
  6f4310b00b9a147241b071a60c28a650827fb03d 644   foo

update to rev 0 with a date

  $ hg upd -d foo 0
  abort: you can't specify a revision and a date
  [10]

update by date

  $ hg update -d '<1970-01-01 00:00:02 +0000'
  found revision 1 from Thu Jan 01 00:00:01 1970 +0000
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg update -d '<1970-01-01 00:00:01 +0000'
  found revision 1 from Thu Jan 01 00:00:01 1970 +0000
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg update -d '<1970-01-01 00:00:00 +0000'
  found revision 0 from Thu Jan 01 00:00:00 1970 +0000
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg update -d '>1970-01-01 00:00:02 +0000'
  abort: revision matching date not found
  [10]
  $ hg update -d '>1970-01-01 00:00:01 +0000'
  found revision 1 from Thu Jan 01 00:00:01 1970 +0000
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg update -d '>1970-01-01 00:00:00 +0000'
  found revision 1 from Thu Jan 01 00:00:01 1970 +0000
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved

update to default destination (with empty revspec)

  $ hg update -q null
  $ hg update
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg id
  84b9316f7b31 tip

  $ hg update -q null
  $ hg update -r ''
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg id
  84b9316f7b31 tip

  $ hg update -q null
  $ hg update ''
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg id
  84b9316f7b31 tip

  $ cd ..

update with worker processes

#if no-windows

  $ cat <<EOF > forceworker.py
  > from mercurial import extensions, worker
  > def nocost(orig, ui, costperop, nops, threadsafe=True):
  >     return worker._numworkers(ui) > 1
  > def uisetup(ui):
  >     extensions.wrapfunction(worker, 'worthwhile', nocost)
  > EOF

  $ hg init worker
  $ cd worker
  $ cat <<EOF >> .hg/hgrc
  > [extensions]
  > forceworker = $TESTTMP/forceworker.py
  > [worker]
  > numcpus = 4
  > EOF
  $ for i in `"$PYTHON" $TESTDIR/seq.py 1 100`; do
  >   echo $i > $i
  > done
  $ hg ci -qAm 'add 100 files'

  $ hg update null
  0 files updated, 0 files merged, 100 files removed, 0 files unresolved
  $ hg update -v | grep 100
  getting 100
  100 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg status

  $ cd ..

#endif