When building this project with [Nix/Crane](https://github.com/ipetkov/crane/discussions/693), if the `jj-cli` dependency is specified in `Cargo.toml` as a git-based crate, `cargo vendor` splits this workspace up into sub-crate directories, which causes `cargo metadata` to fail when searching for relative deps in the workspace root.
This commit simply changes how the crate version is determined, using Cargo's built-in environment variable [`CARGO_PKG_VERSION`](https://doc.rust-lang.org/cargo/reference/environment-variables.html)
Since .git/HEAD is less frequently updated, this should avoid unneeded
recompilation on test-only changes. This only applies to colocated repo.
For non-colocated repo, maybe we can watch src/ and ../lib/src files?
This also adds $NIX_JJ_GIT_HASH to reflect hash changes (and to not rerun
if no .git nor .jj directory exists.)
Since the recent move of `builds.rs` to `cli/build.rs`, incremental
builds re-calcuate the version number and thus result in some
re-compilation and lots of re-linking.
Summary: In preparation for unifying all workspace dependencies across all
crates, let's go ahead and move the jj-cli crate into its own new directory.
This will also be a nicer and more uniform layout as we add new `jj-*` crates.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
Change-Id: Icf94e7ae5f290dc8e181215727b38ada
