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rust-index: find_gca_candidates bit sets genericization...
rust-index: find_gca_candidates bit sets genericization This allows to use arbitratry size of inputs in `find_gca_candidates()`. We're genericizing so that the common case of up to 63 inputs can be treated with the efficient implementation backed by `u64`. Some complications with the borrow checker came, because arbitrary sized bit sets will not be `Copy`, hence mutating them keeps a mut ref on the `seen` vector. This is solved by some cloning, most of which can be avoided, preferably in a follow-up after proof that this works (hence after exposition to Python layer). As far as performance is concerned, calling `clone()` on a `Copy` object (good case when number of revs is less than 64) should end up just doing a copy, according to this excerpt of the `Clone` trait documentation: Types that are Copy should have a trivial implementation of Clone. More formally: if T: Copy, x: T, and y: &T, then let x = y.clone(); is equivalent to let x = *y;. Manual implementations should be careful to uphold this invariant; however, unsafe code must not rely on it to ensure memory safety. We kept the general structure, hence why there are some double negations. This also could be made nicer in a follow-up. The `NonStaticPoisonableBitSet` is included to ensure that the `PoisonableBitSet` trait is general enough (had to correct `vec_of_empty()` for instance). Moving the genericization one level to encompass the `seen` vector and not its elements would be better for performance, if worth it.
Georges Racinet on incendie.racinet.fr -
r52117:43241f31 default
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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.

See hg help config.rhg for details.

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/bin exists and is in $PATH
  • From the repository root, make a symbolic link with
    ln -s rust/target/release/rhg ~/.local/bin/hg
  • Configure ~/.hgrc with:
[rhg]
on-unsupported = fallback
fallback-executable = /usr/bin/hg
allowed-extensions = rebase, absorb

  • Check that the output of running
    hg notarealsubcommand
    starts with hg: unknown command, which indicates fallback.

  • Check that the output of running
    hg notarealsubcommand --config rhg.on-unsupported=abort
    starts with unsupported feature:.