view tests/test-rebase-transaction.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

#testcases continuecommand continueflag
Rebasing using a single transaction

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > rebase=
  > drawdag=$TESTDIR/drawdag.py
  > 
  > [rebase]
  > singletransaction=True
  > 
  > [phases]
  > publish=False
  > 
  > [alias]
  > tglog = log -G --template "{rev}: {desc}"
  > EOF

#if continueflag
  $ cat >> $HGRCPATH <<EOF
  > [alias]
  > continue = rebase --continue
  > EOF
#endif

Check that a simple rebase works

  $ hg init simple && cd simple
  $ hg debugdrawdag <<'EOF'
  >   Z
  >   |
  >   | D
  >   | |
  >   | C
  >   | |
  >   Y B
  >   |/
  >   A
  > EOF
- We should only see one status stored message. It comes from the start.
  $ hg rebase --debug -b D -d Z | grep 'status stored'
  rebase status stored
  $ hg tglog
  o  5: D
  |
  o  4: C
  |
  o  3: B
  |
  o  2: Z
  |
  o  1: Y
  |
  o  0: A
  
  $ cd ..

Check that --collapse works

  $ hg init collapse && cd collapse
  $ hg debugdrawdag <<'EOF'
  >   Z
  >   |
  >   | D
  >   | |
  >   | C
  >   | |
  >   Y B
  >   |/
  >   A
  > EOF
- We should only see two status stored messages. One from the start, one from
- cmdutil.commitforceeditor() which forces tr.writepending()
  $ hg rebase --collapse --debug -b D -d Z | grep 'status stored'
  rebase status stored
  rebase status stored
  $ hg tglog
  o  3: Collapsed revision
  |  * B
  |  * C
  |  * D
  o  2: Z
  |
  o  1: Y
  |
  o  0: A
  
  $ cd ..

With --collapse, check that conflicts can be resolved and rebase can then be
continued

  $ hg init collapse-conflict && cd collapse-conflict
  $ hg debugdrawdag <<'EOF'
  >   Z   # Z/conflict=Z
  >   |
  >   | D
  >   | |
  >   | C # C/conflict=C
  >   | |
  >   Y B
  >   |/
  >   A
  > EOF
  $ hg rebase --collapse -b D -d Z
  rebasing 1:112478962961 B "B"
  rebasing 3:c26739dbe603 C "C"
  merging conflict
  warning: conflicts while merging conflict! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see 'hg resolve', then 'hg rebase --continue')
  [240]
  $ hg tglog
  o  5: D
  |
  | @  4: Z
  | |
  % |  3: C
  | |
  | o  2: Y
  | |
  o |  1: B
  |/
  o  0: A
  
  $ hg st
  M conflict
  A B
  A C
  ? conflict.orig
  $ echo resolved > conflict
  $ hg resolve -m
  (no more unresolved files)
  continue: hg rebase --continue
  $ hg continue
  already rebased 1:112478962961 B "B" as 79bc8f4973ce
  rebasing 3:c26739dbe603 C "C"
  rebasing 5:d24bb333861c D tip "D"
  saved backup bundle to $TESTTMP/collapse-conflict/.hg/strip-backup/112478962961-b5b34645-rebase.hg
  $ hg tglog
  o  3: Collapsed revision
  |  * B
  |  * C
  |  * D
  o  2: Z
  |
  o  1: Y
  |
  o  0: A
  
  $ cd ..

With --collapse, check that the commit message editing can be canceled and
rebase can then be continued

  $ hg init collapse-cancel-editor && cd collapse-cancel-editor
  $ hg debugdrawdag <<'EOF'
  >   Z
  >   |
  >   | D
  >   | |
  >   | C
  >   | |
  >   Y B
  >   |/
  >   A
  > EOF
  $ HGEDITOR=false hg --config ui.interactive=1 rebase --collapse -b D -d Z
  rebasing 1:112478962961 B "B"
  rebasing 3:26805aba1e60 C "C"
  rebasing 5:f585351a92f8 D tip "D"
  transaction abort!
  rollback completed
  abort: edit failed: false exited with status 1
  [250]
  $ hg tglog
  o  5: D
  |
  | o  4: Z
  | |
  o |  3: C
  | |
  | o  2: Y
  | |
  o |  1: B
  |/
  o  0: A
  
  $ hg continue
  rebasing 1:112478962961 B "B"
  rebasing 3:26805aba1e60 C "C"
  rebasing 5:f585351a92f8 D tip "D"
  saved backup bundle to $TESTTMP/collapse-cancel-editor/.hg/strip-backup/112478962961-cb2a9b47-rebase.hg
  $ hg tglog
  o  3: Collapsed revision
  |  * B
  |  * C
  |  * D
  o  2: Z
  |
  o  1: Y
  |
  o  0: A
  
  $ cd ..