| Name | Size | Modified | Last Commit | Author |
|---|---|---|---|---|
| / rust / rhg | ||||
| src | ||||
| Cargo.toml | Loading ... | |||
| README.md | Loading ... | |||
rhg
The rhg executable implements a subset of the functionnality of hg
using only Rust, to avoid the startup cost of a Python interpreter.
This subset is initially small but grows over time as rhg is improved.
When fallback to the Python implementation is configured (see below),
rhg aims to be a drop-in replacement for hg that should behave the same,
except that some commands run faster.
Building
To compile rhg, either run cargo build --release from this rust/rhg/
directory, or run make build-rhg from the repository root.
The executable can then be found at rust/target/release/rhg.
Mercurial configuration
rhg reads Mercurial configuration from the usual sources:
the user’s ~/.hgrc, a repository’s .hg/hgrc, command line --config, etc.
It has some specific configuration in the [rhg] section:
-
on-unsupportedgoverns the behavior ofrhgwhen it encounters something
that it does not support but “full”hgpossibly does.
This can be in configuration, on the command line, or in a repository.abort, the default value, makesrhgprint a message to stderr
to explain what is not supported, then terminate with a 252 exit code.abort-silentmakes it terminate with the same exit code,
but without printing anything.fallbackmakes it silently call a (presumably Python-based)hg
subprocess with the same command-line parameters.
Therhg.fallback-executableconfiguration must be set.
-
fallback-executable: path to the executable to run in a sub-process
when falling back to a Python implementation of Mercurial. -
allowed-extensions: a list of extension names thatrhgcan ignore.Mercurial extensions can modify the behavior of existing
hgsub-commands,
including those thatrhgotherwise supports.
Because it cannot load Python extensions, finding them
enabled in configuration is considered “unsupported” (see above).
A few exceptions are made for extensions thatrhgdoes know about,
with the Rust implementation duplicating their behavior.This configuration makes additional exceptions:
rhgwill proceed even if
those extensions are enabled.
Installation and configuration example
For example, to install rhg as hg for the current user with fallback to
the system-wide install of Mercurial, and allow it to run even though the
rebase and absorb extensions are enabled, on a Unix-like platform:
- Build
rhg(see above) - Make sure the
~/.local/binexists and is in$PATH - From the repository root, make a symbolic link with
ln -s rust/target/release/rhg ~/.local/bin/hg - Configure
~/.hgrcwith:
[rhg]
on-unsupported = fallback
fallback-executable = /usr/bin/hg
allowed-extensions = rebase, absorb
-
Check that the output of running
hg notarealsubcommand
starts withhg: unknown command, which indicates fallback. -
Check that the output of running
hg notarealsubcommand --config rhg.on-unsupported=abort
starts withunsupported feature:.