view tests/test-convert-p4.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 p4

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "convert = " >> $HGRCPATH

create p4 depot
  $ P4ROOT=`pwd`/depot; export P4ROOT
  $ P4AUDIT=$P4ROOT/audit; export P4AUDIT
  $ P4JOURNAL=$P4ROOT/journal; export P4JOURNAL
  $ P4LOG=$P4ROOT/log; export P4LOG
  $ P4PORT=localhost:$HGPORT; export P4PORT
  $ P4DEBUG=1; export P4DEBUG

start the p4 server
  $ [ ! -d $P4ROOT ] && mkdir $P4ROOT
  $ p4d -f -J off >$P4ROOT/stdout 2>$P4ROOT/stderr &
  $ echo $! >> $DAEMON_PIDS
  $ trap "echo stopping the p4 server ; p4 admin stop" EXIT

  $ # wait for the server to initialize
  $ while ! p4 ; do
  >    sleep 1
  > done >/dev/null 2>/dev/null

create a client spec
  $ P4CLIENT=hg-p4-import; export P4CLIENT
  $ DEPOTPATH=//depot/test-mercurial-import/...
  $ p4 client -o | sed '/^View:/,$ d' >p4client
  $ echo View: >>p4client
  $ echo " $DEPOTPATH //$P4CLIENT/..." >>p4client
  $ p4 client -i <p4client
  Client hg-p4-import saved.

populate the depot
  $ echo a > a
  $ mkdir b
  $ echo c > b/c
  $ p4 add a b/c
  //depot/test-mercurial-import/a#1 - opened for add
  //depot/test-mercurial-import/b/c#1 - opened for add
  $ p4 submit -d initial
  Submitting change 1.
  Locking 2 files ...
  add //depot/test-mercurial-import/a#1
  add //depot/test-mercurial-import/b/c#1
  Change 1 submitted.

change some files
  $ p4 edit a
  //depot/test-mercurial-import/a#1 - opened for edit
  $ echo aa >> a
  $ p4 submit -d "change a"
  Submitting change 2.
  Locking 1 files ...
  edit //depot/test-mercurial-import/a#2
  Change 2 submitted.

  $ p4 edit b/c
  //depot/test-mercurial-import/b/c#1 - opened for edit
  $ echo cc >> b/c
  $ p4 submit -d "change b/c"
  Submitting change 3.
  Locking 1 files ...
  edit //depot/test-mercurial-import/b/c#2
  Change 3 submitted.

convert
  $ hg convert -s p4 $DEPOTPATH dst
  initializing destination dst repository
  scanning source...
  reading p4 views
  collecting p4 changelists
  1 initial
  2 change a
  3 change b/c
  sorting...
  converting...
  2 initial
  1 change a
  0 change b/c
  $ hg -R dst log --template 'rev={rev} desc="{desc}" tags="{tags}" files="{files}"\n'
  rev=2 desc="change b/c" tags="tip" files="b/c"
  rev=1 desc="change a" tags="" files="a"
  rev=0 desc="initial" tags="" files="a b/c"

change some files
  $ p4 edit a b/c
  //depot/test-mercurial-import/a#2 - opened for edit
  //depot/test-mercurial-import/b/c#2 - opened for edit
  $ echo aaa >> a
  $ echo ccc >> b/c
  $ p4 submit -d "change a b/c"
  Submitting change 4.
  Locking 2 files ...
  edit //depot/test-mercurial-import/a#3
  edit //depot/test-mercurial-import/b/c#3
  Change 4 submitted.

convert again
  $ hg convert -s p4 $DEPOTPATH dst
  scanning source...
  reading p4 views
  collecting p4 changelists
  4 change a b/c
  sorting...
  converting...
  0 change a b/c
  $ hg -R dst log --template 'rev={rev} desc="{desc}" tags="{tags}" files="{files}"\n'
  rev=3 desc="change a b/c" tags="tip" files="a b/c"
  rev=2 desc="change b/c" tags="" files="b/c"
  rev=1 desc="change a" tags="" files="a"
  rev=0 desc="initial" tags="" files="a b/c"

interesting names
  $ echo dddd > "d d"
  $ mkdir " e"
  $ echo fff >" e/ f"
  $ p4 add "d d" " e/ f"
  //depot/test-mercurial-import/d d#1 - opened for add
  //depot/test-mercurial-import/ e/ f#1 - opened for add
  $ p4 submit -d "add d e f"
  Submitting change 5.
  Locking 2 files ...
  add //depot/test-mercurial-import/ e/ f#1
  add //depot/test-mercurial-import/d d#1
  Change 5 submitted.

convert again
  $ hg convert -s p4 $DEPOTPATH dst
  scanning source...
  reading p4 views
  collecting p4 changelists
  5 add d e f
  sorting...
  converting...
  0 add d e f
  $ hg -R dst log --template 'rev={rev} desc="{desc}" tags="{tags}" files="{files}"\n'
  rev=4 desc="add d e f" tags="tip" files=" e/ f d d"
  rev=3 desc="change a b/c" tags="" files="a b/c"
  rev=2 desc="change b/c" tags="" files="b/c"
  rev=1 desc="change a" tags="" files="a"
  rev=0 desc="initial" tags="" files="a b/c"

empty commit message
  $ p4 edit a
  //depot/test-mercurial-import/a#3 - opened for edit
  $ echo aaaaa >> a
  $ p4 submit -d ""
  Submitting change 6.
  Locking 1 files ...
  edit //depot/test-mercurial-import/a#4
  Change 6 submitted.
  $ hg convert -s p4 $DEPOTPATH dst
  scanning source...
  reading p4 views
  collecting p4 changelists
  6 **empty changelist description**
  sorting...
  converting...
  0 

exit trap:
  stopping the p4 server