view tests/dummyssh @ 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

#!/usr/bin/env python3

from __future__ import absolute_import

import os
import sys

os.chdir(os.getenv('TESTTMP'))

if sys.argv[1] != "user@dummy":
    sys.exit(-1)

os.environ["SSH_CLIENT"] = "%s 1 2" % os.environ.get('LOCALIP', '127.0.0.1')

log = open("dummylog", "ab")
log.write(b"Got arguments")
for i, arg in enumerate(sys.argv[1:]):
    log.write(b" %d:%s" % (i + 1, arg.encode('latin1')))
log.write(b"\n")
log.close()
hgcmd = sys.argv[2]
if os.name == 'nt':
    # hack to make simple unix single quote quoting work on windows
    hgcmd = hgcmd.replace("'", '"')
r = os.system(hgcmd)
sys.exit(bool(r))