view tests/test-issue586.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

Issue586: removing remote files after merge appears to corrupt the
dirstate

  $ hg init a
  $ cd a
  $ echo a > a
  $ hg ci -Ama
  adding a

  $ hg init ../b
  $ cd ../b
  $ echo b > b
  $ hg ci -Amb
  adding b

  $ hg pull -f ../a
  pulling from ../a
  searching for changes
  warning: repository is unrelated
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets cb9a9f314b8b
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg rm -f a
  $ hg ci -Amc

  $ hg st -A
  C b
  $ cd ..

Issue1433: Traceback after two unrelated pull, two move, a merge and
a commit (related to issue586)

create test repos

  $ hg init repoa
  $ touch repoa/a
  $ hg -R repoa ci -Am adda
  adding a

  $ hg init repob
  $ touch repob/b
  $ hg -R repob ci -Am addb
  adding b

  $ hg init repoc
  $ cd repoc
  $ hg pull ../repoa
  pulling from ../repoa
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets 7132ab4568ac
  (run 'hg update' to get a working copy)
  $ hg update
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ mkdir tst
  $ hg mv * tst
  $ hg ci -m "import a in tst"
  $ hg pull -f ../repob
  pulling from ../repob
  searching for changes
  warning: repository is unrelated
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets 5ddceb349652
  (run 'hg heads' to see heads, 'hg merge' to merge)

merge both repos

  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ mkdir src

move b content

  $ hg mv b src
  $ hg ci -m "import b in src"
  $ hg manifest
  src/b
  tst/a

  $ cd ..