// Copyright 2023 The Jujutsu Authors//// Licensed under the Apache License, Version 2.0 (the "License");// you may not use this file except in compliance with the License.// You may obtain a copy of the License at//// https://www.apache.org/licenses/LICENSE-2.0//// Unless required by applicable law or agreed to in writing, software// distributed under the License is distributed on an "AS IS" BASIS,// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.// See the License for the specific language governing permissions and// limitations under the License. use std::path::Path;use std::process::Command;use std::str; use cargo_metadata::MetadataCommand; const GIT_HEAD_PATH: &str = "../.git/HEAD";const JJ_OP_HEADS_PATH: &str = "../.jj/repo/op_heads/heads"; fn main() -> std::io::Result<()> {    let path = std::env::var("CARGO_MANIFEST_DIR").unwrap();    let meta = MetadataCommand::new()        .manifest_path("./Cargo.toml")        .current_dir(&path)        .exec()        .unwrap();    let root = meta.root_package().unwrap();    let version = &root.version;     if Path::new(GIT_HEAD_PATH).exists() {        // In colocated repo, .git/HEAD should reflect the working-copy parent.        println!("cargo:rerun-if-changed={GIT_HEAD_PATH}");    } else if Path::new(JJ_OP_HEADS_PATH).exists() {        // op_heads changes when working-copy files are mutated, which is way more        // frequent than .git/HEAD.        println!("cargo:rerun-if-changed={JJ_OP_HEADS_PATH}");    }    println!("cargo:rerun-if-env-changed=NIX_JJ_GIT_HASH");     if let Some(git_hash) = get_git_hash() {        println!("cargo:rustc-env=JJ_VERSION={}-{}", version, git_hash);    } else {        println!("cargo:rustc-env=JJ_VERSION={}", version);    }     Ok(())} fn get_git_hash() -> Option<String> {    if let Some(nix_hash) = std::env::var("NIX_JJ_GIT_HASH")        .ok()        .filter(|s| !s.is_empty())    {        return Some(nix_hash);    }    if let Ok(output) = Command::new("jj")        .args([            "--ignore-working-copy",            "--color=never",            "log",            "--no-graph",            "-r=@-",            "-T=commit_id",        ])        .output()    {        if output.status.success() {            return Some(String::from_utf8(output.stdout).unwrap());        }    }     if let Ok(output) = Command::new("git").args(["rev-parse", "HEAD"]).output() {        if output.status.success() {            let line = str::from_utf8(&output.stdout).unwrap();            return Some(line.trim_end().to_owned());        }    }     None}