# vergen
Generate build, git, and rustc related 'cargo:rustc-env' instructions via 'build.rs' for use in your code via the env! macro
## Current Release
[](https://crates.io/crates/vergen)
[](https://crates.io/crates/vergen)
[](https://crates.io/crates/vergen)
## Release 4.0 Breaking Changes
* The main entry point for use has changed from `generate_cargo_keys` to `gen`
* There are now 3 features that allow you to control what instructions can be generated (`build`, `git`, and `rustc`).
* The `build` feature enables the `VERGEN_BUILD_*` instructions.
* The `git` feature enables the `VERGEN_GIT_*` instructions, the `cargo:rerun-if-changed` instructions, and the `REBUILD_ON_HEAD_CHANGE` flag.
* The `rustc` feature enables the `VERGEN_RUSTC_*` instructions.
* By default, all three features are enabled.
* You can build with all three features disabled, which basically make the `gen` function a no-op.
* You can still use `ConstantsFlags` to toggle individual cargo instructions.
* The generated instructions have been normalized. Therefore, you may need to update what env variable you are referring to in code. I've included a list below of the full set of instructions that can be generated for reference.
```text, no_run
cargo:rustc-env=VERGEN_BUILD_DATE=2021-02-12
cargo:rustc-env=VERGEN_BUILD_TIMESTAMP=2021-02-12T01:54:15.134750+00:00
cargo:rustc-env=VERGEN_GIT_BRANCH=feature/git2
cargo:rustc-env=VERGEN_GIT_COMMIT_DATE=2021-02-11T20:05:53-05:00
cargo:rustc-env=VERGEN_GIT_SEMVER=v3.2.0-86-g95fc0f5
cargo:rustc-env=VERGEN_GIT_SEMVER_LIGHTWEIGHT=blah-33-g95fc0f5
cargo:rustc-env=VERGEN_GIT_SHA=95fc0f5d066710f16e0c23ce3239d6e040abca0d
cargo:rustc-env=VERGEN_GIT_SHA_SHORT=95fc0f5
cargo:rustc-env=VERGEN_RUSTC_CHANNEL=nightly
cargo:rustc-env=VERGEN_RUSTC_COMMIT_DATE=2021-02-10
cargo:rustc-env=VERGEN_RUSTC_COMMIT_HASH=07194ffcd25b0871ce560b9f702e52db27ac9f77
cargo:rustc-env=VERGEN_RUSTC_HOST_TRIPLE=x86_64-apple-darwin
cargo:rustc-env=VERGEN_RUSTC_LLVM_VERSION=11.0
cargo:rustc-env=VERGEN_RUSTC_SEMVER=1.52.0-nightly
cargo:rerun-if-changed=/Users/yoda/projects/rust-lang/vergen/.git/HEAD
cargo:rerun-if-changed=/Users/yoda/projects/rust-lang/vergen/.git/refs/heads/feature/git2
```
* Under the hood, the `Command`s used for git have been removed in lieu of using the `git2` library directly.
* `git2` is also used to determine the `HEAD` path and the path that it refers to for the `cargo:rerun-if-changed` instructions. This is more reliable then the manual method that was in place before.
* I've migrated the CI stuff from Travis to GitHub Actions.
## Build Status
## Code Coverage
[](https://codecov.io/gh/rustyhorde/vergen)
## Documentation
[](https://docs.rs/vergen)
## Example Usage
See the documentation at [docs.rs](https://docs.rs/vergen/3.2.0/vergen/#cargo-key-build-script-output) for example usage
## License
Licensed under either of
* Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
* MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
at your option.
### Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any
additional terms or conditions.