// 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; const GIT_HEAD_PATH: &str = "../.git/HEAD";const JJ_OP_HEADS_PATH: &str = "../.jj/repo/op_heads/heads"; fn main() {    let version = std::env::var("CARGO_PKG_VERSION").unwrap();     println!("cargo:rerun-if-env-changed=NIX_JJ_GIT_HASH");    let git_hash = get_git_hash_from_nix().or_else(|| {        if Path::new(GIT_HEAD_PATH).exists() {            // In colocated workspace, .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}");        }        get_git_hash_from_jj().or_else(get_git_hash_from_git)    });     if let Some(git_hash) = git_hash {        println!("cargo:rustc-env=JJ_VERSION={version}-{git_hash}");    } else {        println!("cargo:rustc-env=JJ_VERSION={version}");    }     let docs_symlink_path = Path::new("docs");    println!("cargo:rerun-if-changed={}", docs_symlink_path.display());    if docs_symlink_path.join("index.md").exists() {        println!("cargo:rustc-env=JJ_DOCS_DIR=docs/");    } else {        println!("cargo:rustc-env=JJ_DOCS_DIR=../docs/");    }} fn get_git_hash_from_nix() -> Option<String> {    std::env::var("NIX_JJ_GIT_HASH")        .ok()        .filter(|s| !s.is_empty())} fn get_git_hash_from_jj() -> Option<String> {    Command::new("jj")        .args([            "--ignore-working-copy",            "--color=never",            "log",            "--no-graph",            "-r=@-",            "-T=commit_id ++ '-'",        ])        .output()        .ok()        .filter(|output| output.status.success())        .map(|output| {            let mut parent_commits = String::from_utf8(output.stdout).unwrap();            // If a development version of `jj` is compiled at a merge commit, this will            // result in several commit ids separated by `-`s.            parent_commits.truncate(parent_commits.trim_end_matches('-').len());            parent_commits        })} fn get_git_hash_from_git() -> Option<String> {    Command::new("git")        .args(["rev-parse", "HEAD"])        .output()        .ok()        .filter(|output| output.status.success())        .map(|output| {            str::from_utf8(&output.stdout)                .unwrap()                .trim_end()                .to_owned()        })}