view tests/test-remotefilelog-local.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

#require no-windows

  $ . "$TESTDIR/remotefilelog-library.sh"

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > EOF
  $ echo x > x
  $ echo y > y
  $ echo z > z
  $ hg commit -qAm xy

  $ cd ..

  $ hgcloneshallow ssh://user@dummy/master shallow -q
  3 files fetched over 1 fetches - (3 misses, 0.00% hit ratio) over *s (glob)
  $ cd shallow

# status

  $ clearcache
  $ echo xx > x
  $ echo yy > y
  $ touch a
  $ hg status
  M x
  M y
  ? a
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)
  $ hg add a
  $ hg status
  M x
  M y
  A a

# diff

  $ hg debugrebuilddirstate # fixes dirstate non-determinism
  $ hg add a
  $ clearcache
  $ hg diff
  diff -r f3d0bb0d1e48 x
  --- a/x* (glob)
  +++ b/x* (glob)
  @@ -1,1 +1,1 @@
  -x
  +xx
  diff -r f3d0bb0d1e48 y
  --- a/y* (glob)
  +++ b/y* (glob)
  @@ -1,1 +1,1 @@
  -y
  +yy
  3 files fetched over 1 fetches - (3 misses, 0.00% hit ratio) over *s (glob)

# local commit

  $ clearcache
  $ echo a > a
  $ echo xxx > x
  $ echo yyy > y
  $ hg commit -m a
  ? files fetched over 1 fetches - (? misses, 0.00% hit ratio) over *s (glob)

# local commit where the dirstate is clean -- ensure that we do just one fetch
# (update to a commit on the server first)

  $ hg --config debug.dirstate.delaywrite=1 up 0
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ clearcache
  $ hg debugdirstate
  n 644          2 * x (glob)
  n 644          2 * y (glob)
  n 644          2 * z (glob)
  $ echo xxxx > x
  $ echo yyyy > y
  $ hg commit -m x
  created new head
  2 files fetched over 1 fetches - (2 misses, 0.00% hit ratio) over *s (glob)

# restore state for future tests

  $ hg -q strip .
  $ hg -q up tip

# rebase

  $ clearcache
  $ cd ../master
  $ echo w > w
  $ hg commit -qAm w

  $ cd ../shallow
  $ hg pull
  pulling from ssh://user@dummy/master
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files (+1 heads)
  new changesets fed61014d323
  (run 'hg heads' to see heads, 'hg merge' to merge)

  $ hg rebase -d tip
  rebasing 1:9abfe7bca547 "a"
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/9abfe7bca547-8b11e5ff-rebase.hg (glob)
  3 files fetched over 2 fetches - (3 misses, 0.00% hit ratio) over *s (glob)

# strip

  $ clearcache
  $ hg debugrebuilddirstate # fixes dirstate non-determinism
  $ hg strip -r .
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/19edf50f4de7-df3d0f74-backup.hg (glob)
  4 files fetched over 2 fetches - (4 misses, 0.00% hit ratio) over *s (glob)

# unbundle

  $ clearcache
  $ ls -A
  .hg
  w
  x
  y
  z

  $ hg debugrebuilddirstate # fixes dirstate non-determinism
  $ hg unbundle .hg/strip-backup/19edf50f4de7-df3d0f74-backup.hg
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files
  new changesets 19edf50f4de7 (1 drafts)
  (run 'hg update' to get a working copy)

  $ hg up
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  4 files fetched over 1 fetches - (4 misses, 0.00% hit ratio) over *s (glob)
  $ cat a
  a

# revert

  $ clearcache
  $ hg revert -r .~2 y z
  no changes needed to z
  2 files fetched over 2 fetches - (2 misses, 0.00% hit ratio) over *s (glob)
  $ hg checkout -C -r . -q

# explicit bundle should produce full bundle file

  $ hg bundle -r 2 --base 1 ../local.bundle
  1 changesets found
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)
  $ cd ..

  $ hgcloneshallow ssh://user@dummy/master shallow2 -q
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)
  $ cd shallow2
  $ hg unbundle ../local.bundle
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 3 changes to 3 files
  new changesets 19edf50f4de7 (1 drafts)
  (run 'hg update' to get a working copy)

  $ hg log -r 2 --stat
  changeset:   2:19edf50f4de7
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     a
  
   a |  1 +
   x |  2 +-
   y |  2 +-
   3 files changed, 3 insertions(+), 2 deletions(-)
  
# Merge

  $ echo merge >> w
  $ hg commit -m w
  created new head
  $ hg merge 2
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -m merge
  $ hg strip -q -r ".^"

# commit without producing new node

  $ cd $TESTTMP
  $ hgcloneshallow ssh://user@dummy/master shallow3 -q
  $ cd shallow3
  $ echo 1 > A
  $ hg commit -m foo -A A
  $ hg log -r . -T '{node}\n'
  383ce605500277f879b7460a16ba620eb6930b7f
  $ hg update -r '.^' -q
  $ echo 1 > A
  $ hg commit -m foo -A A
  warning: commit already existed in the repository!
  $ hg log -r . -T '{node}\n'
  383ce605500277f879b7460a16ba620eb6930b7f