Mercurial > hg
view tests/test-close-head.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 `$PATH` as `hg`, since the other `hg.py` executable needs
to still be available… somewhere. Eventually this could be replaced
by using PyOxidizer to a have a single executable that embeds a Python
interpreter, but only starts it when needed.
Differential Revision: https://phab.mercurial-scm.org/D10093
author | Simon Sapin <simon.sapin@octobus.net> |
---|---|
date | Mon, 01 Mar 2021 20:36:06 +0100 |
parents | fdd4d668ceb5 |
children |
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$ hg init test-content $ cd test-content $ hg debugbuilddag '+2*2*3*4+7' $ hg bookmark -r 1 @ $ hg log -G --template '{rev}:{node|short}' o 11:1d876b1f862c | o 10:ea5f71948eb8 | o 9:f1b0356d867a | o 8:e8d1253fb0d7 | o 7:d423bbba4459 | o 6:a2f58e9c1e56 | o 5:3a367db1fabc | o 4:e7bd5218ca15 | | o 3:6100d3090acf |/ | o 2:fa942426a6fd |/ | o 1:66f7d451a68b |/ o 0:1ea73414a91b $ hg --config extensions.closehead= close-head -m 'Not a head' 0 1 abort: revision is not an open head: 0 [255] $ hg --config extensions.closehead= close-head -m 'Not a head' -r 0 1 abort: revision is not an open head: 0 [255] $ hg id 000000000000 $ hg --config extensions.closehead= close-head -m 'Close old heads' -r 1 2 $ hg id 000000000000 $ hg bookmark @ 1:66f7d451a68b $ hg heads changeset: 11:1d876b1f862c user: debugbuilddag date: Thu Jan 01 00:00:11 1970 +0000 summary: r11 changeset: 3:6100d3090acf parent: 0:1ea73414a91b user: debugbuilddag date: Thu Jan 01 00:00:03 1970 +0000 summary: r3 $ hg --config extensions.closehead= close-head -m 'Close more old heads' -r 11 $ hg heads changeset: 3:6100d3090acf parent: 0:1ea73414a91b user: debugbuilddag date: Thu Jan 01 00:00:03 1970 +0000 summary: r3 $ hg --config extensions.closehead= close-head -m 'Not a head' 0 abort: revision is not an open head: 0 [255] $ hg --config extensions.closehead= close-head -m 'Already closed head' 1 abort: revision is not an open head: 1 [255] $ hg init ../test-empty $ cd ../test-empty $ hg debugbuilddag '+1' $ hg log -G --template '{rev}:{node|short}' o 0:1ea73414a91b $ hg --config extensions.closehead= close-head -m 'Close initial revision' 0 $ hg heads [1]