view tests/test-patchbomb-bookmark.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

Create @ bookmark as main reference

  $ hg init repo
  $ cd repo
  $ echo "[extensions]" >> $HGRCPATH
  $ echo "patchbomb=" >> $HGRCPATH
  $ hg book @

Create a dummy revision that must never be exported

  $ echo no > no
  $ hg ci -Amno -d '6 0'
  adding no

Create a feature and use -B

  $ hg book booktest
  $ echo first > a
  $ hg ci -Amfirst -d '7 0'
  adding a
  $ echo second > b
  $ hg ci -Amsecond -d '8 0'
  adding b
  $ hg email --date '1981-1-1 0:1' -n -t foo -s bookmark -B booktest
  From [test]: test
  this patch series consists of 2 patches.
  
  
  Write the introductory message for the patch series.
  
  Cc: 
  
  displaying [PATCH 0 of 2] bookmark ...
  MIME-Version: 1.0
  Content-Type: text/plain; charset="us-ascii"
  Content-Transfer-Encoding: 7bit
  Subject: [PATCH 0 of 2] bookmark
  Message-Id: <patchbomb.347155260@test-hostname>
  User-Agent: Mercurial-patchbomb/* (glob)
  Date: Thu, 01 Jan 1981 00:01:00 +0000
  From: test
  To: foo
  
  
  displaying [PATCH 1 of 2] first ...
  MIME-Version: 1.0
  Content-Type: text/plain; charset="us-ascii"
  Content-Transfer-Encoding: 7bit
  Subject: [PATCH 1 of 2] first
  X-Mercurial-Node: accde9b8b6dce861c185d0825c1affc09a79cb26
  X-Mercurial-Series-Index: 1
  X-Mercurial-Series-Total: 2
  Message-Id: <accde9b8b6dce861c185.347155261@test-hostname>
  X-Mercurial-Series-Id: <accde9b8b6dce861c185.347155261@test-hostname>
  In-Reply-To: <patchbomb.347155260@test-hostname>
  References: <patchbomb.347155260@test-hostname>
  User-Agent: Mercurial-patchbomb/* (glob)
  Date: Thu, 01 Jan 1981 00:01:01 +0000
  From: test
  To: foo
  
  # HG changeset patch
  # User test
  # Date 7 0
  #      Thu Jan 01 00:00:07 1970 +0000
  # Node ID accde9b8b6dce861c185d0825c1affc09a79cb26
  # Parent  043bd3889e5aaf7d88fe3713cf425f782ad2fb71
  first
  
  diff -r 043bd3889e5a -r accde9b8b6dc a
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/a	Thu Jan 01 00:00:07 1970 +0000
  @@ -0,0 +1,1 @@
  +first
  
  displaying [PATCH 2 of 2] second ...
  MIME-Version: 1.0
  Content-Type: text/plain; charset="us-ascii"
  Content-Transfer-Encoding: 7bit
  Subject: [PATCH 2 of 2] second
  X-Mercurial-Node: 417defd1559c396ba06a44dce8dc1c2d2d653f3f
  X-Mercurial-Series-Index: 2
  X-Mercurial-Series-Total: 2
  Message-Id: <417defd1559c396ba06a.347155262@test-hostname>
  X-Mercurial-Series-Id: <accde9b8b6dce861c185.347155261@test-hostname>
  In-Reply-To: <patchbomb.347155260@test-hostname>
  References: <patchbomb.347155260@test-hostname>
  User-Agent: Mercurial-patchbomb/* (glob)
  Date: Thu, 01 Jan 1981 00:01:02 +0000
  From: test
  To: foo
  
  # HG changeset patch
  # User test
  # Date 8 0
  #      Thu Jan 01 00:00:08 1970 +0000
  # Node ID 417defd1559c396ba06a44dce8dc1c2d2d653f3f
  # Parent  accde9b8b6dce861c185d0825c1affc09a79cb26
  second
  
  diff -r accde9b8b6dc -r 417defd1559c b
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/b	Thu Jan 01 00:00:08 1970 +0000
  @@ -0,0 +1,1 @@
  +second
  
Do the same and combine with -o only one must be exported

  $ cd ..
  $ hg clone repo repo2
  updating to bookmark @
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd repo
  $ hg up @
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  (activating bookmark @)
  $ hg book outgoing
  $ echo 1 > x
  $ hg ci -Am1 -d '8 0'
  adding x
  created new head
  $ hg push ../repo2 -B outgoing
  pushing to ../repo2
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  exporting bookmark outgoing
  $ echo 2 > y
  $ hg ci -Am2 -d '9 0'
  adding y
  $ hg email --date '1982-1-1 0:1' -n -t foo -s bookmark -B outgoing -o ../repo2
  comparing with ../repo2
  From [test]: test
  this patch series consists of 1 patches.
  
  Cc: 
  
  displaying [PATCH] bookmark ...
  MIME-Version: 1.0
  Content-Type: text/plain; charset="us-ascii"
  Content-Transfer-Encoding: 7bit
  Subject: [PATCH] bookmark
  X-Mercurial-Node: 8dab2639fd35f1e337ad866c372a5c44f1064e3c
  X-Mercurial-Series-Index: 1
  X-Mercurial-Series-Total: 1
  Message-Id: <8dab2639fd35f1e337ad.378691260@test-hostname>
  X-Mercurial-Series-Id: <8dab2639fd35f1e337ad.378691260@test-hostname>
  User-Agent: Mercurial-patchbomb/* (glob)
  Date: Fri, 01 Jan 1982 00:01:00 +0000
  From: test
  To: foo
  
  # HG changeset patch
  # User test
  # Date 9 0
  #      Thu Jan 01 00:00:09 1970 +0000
  # Node ID 8dab2639fd35f1e337ad866c372a5c44f1064e3c
  # Parent  0b24b8316483bf30bfc3e4d4168e922b169dbe66
  2
  
  diff -r 0b24b8316483 -r 8dab2639fd35 y
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/y	Thu Jan 01 00:00:09 1970 +0000
  @@ -0,0 +1,1 @@
  +2