view tests/test-rebase-detach.t @ 46706:93e9f448273c

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

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > rebase=
  > 
  > [alias]
  > tglog = log -G --template "{rev}: {node|short} '{desc}'\n"
  > 
  > [extensions]
  > drawdag=$TESTDIR/drawdag.py
  > EOF

Rebasing D onto B detaching from C (one commit):

  $ hg init a1
  $ cd a1

  $ hg debugdrawdag <<EOF
  > D
  > |
  > C B
  > |/
  > A
  > EOF
  $ hg phase --force --secret D

  $ hg rebase -s D -d B
  rebasing 3:e7b3f00ed42e D tip "D"
  saved backup bundle to $TESTTMP/a1/.hg/strip-backup/e7b3f00ed42e-6f368371-rebase.hg

  $ hg log -G --template "{rev}:{phase} '{desc}' {branches}\n"
  o  3:secret 'D'
  |
  | o  2:draft 'C'
  | |
  o |  1:draft 'B'
  |/
  o  0:draft 'A'
  
  $ hg manifest --rev tip
  A
  B
  D

  $ cd ..


Rebasing D onto B detaching from C (two commits):

  $ hg init a2
  $ cd a2

  $ hg debugdrawdag <<EOF
  > E
  > |
  > D
  > |
  > C B
  > |/
  > A
  > EOF

  $ hg rebase -s D -d B
  rebasing 3:e7b3f00ed42e D "D"
  rebasing 4:69a34c08022a E tip "E"
  saved backup bundle to $TESTTMP/a2/.hg/strip-backup/e7b3f00ed42e-a2ec7cea-rebase.hg

  $ hg tglog
  o  4: ee79e0744528 'E'
  |
  o  3: 10530e1d72d9 'D'
  |
  | o  2: dc0947a82db8 'C'
  | |
  o |  1: 112478962961 'B'
  |/
  o  0: 426bada5c675 'A'
  
  $ hg manifest --rev tip
  A
  B
  D
  E

  $ cd ..

Rebasing C onto B using detach (same as not using it):

  $ hg init a3
  $ cd a3

  $ hg debugdrawdag <<EOF
  > D
  > |
  > C B
  > |/
  > A
  > EOF

  $ hg rebase -s C -d B
  rebasing 2:dc0947a82db8 C "C"
  rebasing 3:e7b3f00ed42e D tip "D"
  saved backup bundle to $TESTTMP/a3/.hg/strip-backup/dc0947a82db8-b8481714-rebase.hg

  $ hg tglog
  o  3: 7375f3dbfb0f 'D'
  |
  o  2: bbfdd6cb49aa 'C'
  |
  o  1: 112478962961 'B'
  |
  o  0: 426bada5c675 'A'
  
  $ hg manifest --rev tip
  A
  B
  C
  D

  $ cd ..


Rebasing D onto B detaching from C and collapsing:

  $ hg init a4
  $ cd a4

  $ hg debugdrawdag <<EOF
  > E
  > |
  > D
  > |
  > C B
  > |/
  > A
  > EOF
  $ hg phase --force --secret E

  $ hg rebase --collapse -s D -d B
  rebasing 3:e7b3f00ed42e D "D"
  rebasing 4:69a34c08022a E tip "E"
  saved backup bundle to $TESTTMP/a4/.hg/strip-backup/e7b3f00ed42e-a2ec7cea-rebase.hg

  $ hg  log -G --template "{rev}:{phase} '{desc}' {branches}\n"
  o  3:secret 'Collapsed revision
  |  * D
  |  * E'
  | o  2:draft 'C'
  | |
  o |  1:draft 'B'
  |/
  o  0:draft 'A'
  
  $ hg manifest --rev tip
  A
  B
  D
  E

  $ cd ..

Rebasing across null as ancestor
  $ hg init a5
  $ cd a5

  $ hg debugdrawdag <<EOF
  > E
  > |
  > D
  > |
  > C
  > |
  > A B
  > EOF

  $ hg rebase -s C -d B
  rebasing 2:dc0947a82db8 C "C"
  rebasing 3:e7b3f00ed42e D "D"
  rebasing 4:69a34c08022a E tip "E"
  saved backup bundle to $TESTTMP/a5/.hg/strip-backup/dc0947a82db8-3eefec98-rebase.hg

  $ hg tglog
  o  4: e3d0c70d606d 'E'
  |
  o  3: e9153d36a1af 'D'
  |
  o  2: a7ac28b870a8 'C'
  |
  o  1: fc2b737bb2e5 'B'
  
  o  0: 426bada5c675 'A'
  
  $ hg rebase -d 1 -s 3
  rebasing 3:e9153d36a1af "D"
  rebasing 4:e3d0c70d606d tip "E"
  saved backup bundle to $TESTTMP/a5/.hg/strip-backup/e9153d36a1af-db7388ed-rebase.hg
  $ hg tglog
  o  4: 2c24e540eccd 'E'
  |
  o  3: 73f786ed52ff 'D'
  |
  | o  2: a7ac28b870a8 'C'
  |/
  o  1: fc2b737bb2e5 'B'
  
  o  0: 426bada5c675 'A'
  
  $ cd ..

Verify that target is not selected as external rev (issue3085)

  $ hg init a6
  $ cd a6

  $ hg debugdrawdag <<EOF
  > H
  > | G
  > |/|
  > F E
  > |/
  > A
  > EOF
  $ hg up -q G

  $ echo "I" >> E
  $ hg ci -m "I"
  $ hg tag --local I
  $ hg merge H
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -m "Merge"
  $ echo "J" >> F
  $ hg ci -m "J"
  $ hg tglog
  @  7: c6aaf0d259c0 'J'
  |
  o    6: 0cfbc7e8faaf 'Merge'
  |\
  | o  5: b92d164ad3cb 'I'
  | |
  o |  4: 4ea5b230dea3 'H'
  | |
  | o  3: c6001eacfde5 'G'
  |/|
  o |  2: 8908a377a434 'F'
  | |
  | o  1: 7fb047a69f22 'E'
  |/
  o  0: 426bada5c675 'A'
  
  $ hg rebase -s I -d H --collapse --config ui.merge=internal:other
  rebasing 5:b92d164ad3cb I "I"
  rebasing 6:0cfbc7e8faaf "Merge"
  rebasing 7:c6aaf0d259c0 tip "J"
  saved backup bundle to $TESTTMP/a6/.hg/strip-backup/b92d164ad3cb-88fd7ab7-rebase.hg

  $ hg tglog
  @  5: 65079693dac4 'Collapsed revision
  |  * I
  |  * Merge
  |  * J'
  o  4: 4ea5b230dea3 'H'
  |
  | o  3: c6001eacfde5 'G'
  |/|
  o |  2: 8908a377a434 'F'
  | |
  | o  1: 7fb047a69f22 'E'
  |/
  o  0: 426bada5c675 'A'
  

  $ hg log --rev tip
  changeset:   5:65079693dac4
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     Collapsed revision
  

  $ cd ..

Ensure --continue restores a correct state (issue3046) and phase:
  $ hg init a7
  $ cd a7

  $ hg debugdrawdag <<EOF
  > C B
  > |/
  > A
  > EOF
  $ hg up -q C
  $ echo 'B2' > B
  $ hg ci -A -m 'B2'
  adding B
  $ hg phase --force --secret .
  $ hg rebase -s . -d B --config ui.merge=internal:merge
  rebasing 3:17b4880d2402 tip "B2"
  merging B
  warning: conflicts while merging B! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see 'hg resolve', then 'hg rebase --continue')
  [240]
  $ hg resolve --all -t internal:local
  (no more unresolved files)
  continue: hg rebase --continue
  $ hg rebase -c
  rebasing 3:17b4880d2402 tip "B2"
  note: not rebasing 3:17b4880d2402 tip "B2", its destination already has all its changes
  saved backup bundle to $TESTTMP/a7/.hg/strip-backup/17b4880d2402-1ae1f6cc-rebase.hg
  $ hg  log -G --template "{rev}:{phase} '{desc}' {branches}\n"
  o  2:draft 'C'
  |
  | @  1:draft 'B'
  |/
  o  0:draft 'A'
  

  $ cd ..