6 files changed, 377 insertions, 362 deletions

diff --git a/xtask/src/cmd.rs b/xtask/src/cmd.rs
new file mode 100644
index 000000000..2027f4893
--- /dev/null
+++ b/xtask/src/cmd.rs
@@ -0,0 +1,53 @@
+use std::process::{Command, Output, Stdio};
+
+use anyhow::{Context, Result};
+
+use crate::project_root;
+
+pub struct Cmd<'a> {
+    pub unix: &'a str,
+    pub windows: &'a str,
+    pub work_dir: &'a str,
+}
+
+impl Cmd<'_> {
+    pub fn run(self) -> Result<()> {
+        if cfg!(windows) {
+            run(self.windows, self.work_dir)
+        } else {
+            run(self.unix, self.work_dir)
+        }
+    }
+    pub fn run_with_output(self) -> Result<Output> {
+        if cfg!(windows) {
+            run_with_output(self.windows, self.work_dir)
+        } else {
+            run_with_output(self.unix, self.work_dir)
+        }
+    }
+}
+
+pub fn run(cmdline: &str, dir: &str) -> Result<()> {
+    do_run(cmdline, dir, &mut |c| {
+        c.stdout(Stdio::inherit());
+    })
+    .map(|_| ())
+}
+
+pub fn run_with_output(cmdline: &str, dir: &str) -> Result<Output> {
+    do_run(cmdline, dir, &mut |_| {})
+}
+
+fn do_run(cmdline: &str, dir: &str, f: &mut dyn FnMut(&mut Command)) -> Result<Output> {
+    eprintln!("\nwill run: {}", cmdline);
+    let proj_dir = project_root().join(dir);
+    let mut args = cmdline.split_whitespace();
+    let exec = args.next().unwrap();
+    let mut cmd = Command::new(exec);
+    f(cmd.args(args).current_dir(proj_dir).stderr(Stdio::inherit()));
+    let output = cmd.output().with_context(|| format!("running `{}`", cmdline))?;
+    if !output.status.success() {
+        anyhow::bail!("`{}` exited with {}", cmdline, output.status);
+    }
+    Ok(output)
+}
diff --git a/xtask/src/help.rs b/xtask/src/help.rs
deleted file mode 100644
index f4e25dcde..000000000
--- a/xtask/src/help.rs
+++ /dev/null
@@ -1,46 +0,0 @@
-//! FIXME: write short doc here
-
-pub const GLOBAL_HELP: &str = "tasks
-
-USAGE:
-    ra_tools <SUBCOMMAND>
-
-FLAGS:
-    -h, --help       Prints help information
-
-SUBCOMMANDS:
-    format
-    install-pre-commit-hook
-    fuzz-tests
-    codegen
-    install
-    lint";
-
-pub const INSTALL_HELP: &str = "ra_tools-install
-
-USAGE:
-    ra_tools.exe install [FLAGS]
-
-FLAGS:
-        --client-code
-    -h, --help           Prints help information
-        --jemalloc
-        --server";
-
-pub fn print_no_param_subcommand_help(subcommand: &str) {
-    eprintln!(
-        "ra_tools-{}
-
-USAGE:
-    ra_tools {}
-
-FLAGS:
-    -h, --help       Prints help information",
-        subcommand, subcommand
-    );
-}
-
-pub const INSTALL_RA_CONFLICT: &str =
-    "error: The argument `--server` cannot be used with `--client-code`
-
-For more information try --help";
diff --git a/xtask/src/install.rs b/xtask/src/install.rs
new file mode 100644
index 000000000..fa82633de
--- /dev/null
+++ b/xtask/src/install.rs
@@ -0,0 +1,178 @@
+//! Installs rust-analyzer language server and/or editor plugin.
+
+use std::{env, path::PathBuf, str};
+
+use anyhow::{Context, Result};
+
+use crate::cmd::{run, run_with_output, Cmd};
+
+// Latest stable, feel free to send a PR if this lags behind.
+const REQUIRED_RUST_VERSION: u32 = 40;
+
+pub struct InstallCmd {
+    pub client: Option<ClientOpt>,
+    pub server: Option<ServerOpt>,
+}
+
+pub enum ClientOpt {
+    VsCode,
+}
+
+pub struct ServerOpt {
+    pub jemalloc: bool,
+}
+
+impl InstallCmd {
+    pub fn run(self) -> Result<()> {
+        if cfg!(target_os = "macos") {
+            fix_path_for_mac().context("Fix path for mac")?
+        }
+        if let Some(server) = self.server {
+            install_server(server).context("install server")?;
+        }
+        if let Some(client) = self.client {
+            install_client(client).context("install client")?;
+        }
+        Ok(())
+    }
+}
+
+fn fix_path_for_mac() -> Result<()> {
+    let mut vscode_path: Vec<PathBuf> = {
+        const COMMON_APP_PATH: &str =
+            r"/Applications/Visual Studio Code.app/Contents/Resources/app/bin";
+        const ROOT_DIR: &str = "";
+        let home_dir = match env::var("HOME") {
+            Ok(home) => home,
+            Err(e) => anyhow::bail!("Failed getting HOME from environment with error: {}.", e),
+        };
+
+        [ROOT_DIR, &home_dir]
+            .iter()
+            .map(|dir| String::from(*dir) + COMMON_APP_PATH)
+            .map(PathBuf::from)
+            .filter(|path| path.exists())
+            .collect()
+    };
+
+    if !vscode_path.is_empty() {
+        let vars = match env::var_os("PATH") {
+            Some(path) => path,
+            None => anyhow::bail!("Could not get PATH variable from env."),
+        };
+
+        let mut paths = env::split_paths(&vars).collect::<Vec<_>>();
+        paths.append(&mut vscode_path);
+        let new_paths = env::join_paths(paths).context("build env PATH")?;
+        env::set_var("PATH", &new_paths);
+    }
+
+    Ok(())
+}
+
+fn install_client(ClientOpt::VsCode: ClientOpt) -> Result<()> {
+    let npm_version = Cmd {
+        unix: r"npm --version",
+        windows: r"cmd.exe /c npm --version",
+        work_dir: "./editors/code",
+    }
+    .run();
+
+    if npm_version.is_err() {
+        eprintln!("\nERROR: `npm --version` failed, `npm` is required to build the VS Code plugin")
+    }
+
+    Cmd { unix: r"npm install", windows: r"cmd.exe /c npm install", work_dir: "./editors/code" }
+        .run()?;
+    Cmd {
+        unix: r"npm run package --scripts-prepend-node-path",
+        windows: r"cmd.exe /c npm run package",
+        work_dir: "./editors/code",
+    }
+    .run()?;
+
+    let code_binary = ["code", "code-insiders", "codium", "code-oss"].iter().find(|bin| {
+        Cmd {
+            unix: &format!("{} --version", bin),
+            windows: &format!("cmd.exe /c {}.cmd --version", bin),
+            work_dir: "./editors/code",
+        }
+        .run()
+        .is_ok()
+    });
+
+    let code_binary = match code_binary {
+        Some(it) => it,
+        None => anyhow::bail!("Can't execute `code --version`. Perhaps it is not in $PATH?"),
+    };
+
+    Cmd {
+        unix: &format!(r"{} --install-extension ./ra-lsp-0.0.1.vsix --force", code_binary),
+        windows: &format!(
+            r"cmd.exe /c {}.cmd --install-extension ./ra-lsp-0.0.1.vsix --force",
+            code_binary
+        ),
+        work_dir: "./editors/code",
+    }
+    .run()?;
+
+    let output = Cmd {
+        unix: &format!(r"{} --list-extensions", code_binary),
+        windows: &format!(r"cmd.exe /c {}.cmd --list-extensions", code_binary),
+        work_dir: ".",
+    }
+    .run_with_output()?;
+
+    if !str::from_utf8(&output.stdout)?.contains("ra-lsp") {
+        anyhow::bail!(
+            "Could not install the Visual Studio Code extension. \
+             Please make sure you have at least NodeJS 10.x together with the latest version of VS Code installed and try again."
+        );
+    }
+
+    Ok(())
+}
+
+fn install_server(opts: ServerOpt) -> Result<()> {
+    let mut old_rust = false;
+    if let Ok(output) = run_with_output("cargo --version", ".") {
+        if let Ok(stdout) = String::from_utf8(output.stdout) {
+            println!("{}", stdout);
+            if !check_version(&stdout, REQUIRED_RUST_VERSION) {
+                old_rust = true;
+            }
+        }
+    }
+
+    if old_rust {
+        eprintln!(
+            "\nWARNING: at least rust 1.{}.0 is required to compile rust-analyzer\n",
+            REQUIRED_RUST_VERSION,
+        )
+    }
+
+    let res = if opts.jemalloc {
+        run("cargo install --path crates/ra_lsp_server --locked --force --features jemalloc", ".")
+    } else {
+        run("cargo install --path crates/ra_lsp_server --locked --force", ".")
+    };
+
+    if res.is_err() && old_rust {
+        eprintln!(
+            "\nWARNING: at least rust 1.{}.0 is required to compile rust-analyzer\n",
+            REQUIRED_RUST_VERSION,
+        )
+    }
+
+    res
+}
+
+fn check_version(version_output: &str, min_minor_version: u32) -> bool {
+    // Parse second the number out of
+    //      cargo 1.39.0-beta (1c6ec66d5 2019-09-30)
+    let minor: Option<u32> = version_output.split('.').nth(1).and_then(|it| it.parse().ok());
+    match minor {
+        None => true,
+        Some(minor) => minor >= min_minor_version,
+    }
+}
diff --git a/xtask/src/lib.rs b/xtask/src/lib.rs
index 51a868dee..e46c21db7 100644
--- a/xtask/src/lib.rs
+++ b/xtask/src/lib.rs
@@ -1,18 +1,22 @@
 //! FIXME: write short doc here
 
+mod cmd;
+pub mod install;
+pub mod pre_commit;
+
 pub mod codegen;
 mod ast_src;
 
 use anyhow::Context;
-pub use anyhow::Result;
 use std::{
     env, fs,
-    io::{Error as IoError, ErrorKind},
     path::{Path, PathBuf},
-    process::{Command, Output, Stdio},
+    process::{Command, Stdio},
 };
 
-use crate::codegen::Mode;
+use crate::{cmd::run, codegen::Mode};
+
+pub use anyhow::Result;
 
 const TOOLCHAIN: &str = "stable";
 
@@ -26,40 +30,6 @@ pub fn project_root() -> PathBuf {
     .to_path_buf()
 }
 
-pub struct Cmd<'a> {
-    pub unix: &'a str,
-    pub windows: &'a str,
-    pub work_dir: &'a str,
-}
-
-impl Cmd<'_> {
-    pub fn run(self) -> Result<()> {
-        if cfg!(windows) {
-            run(self.windows, self.work_dir)
-        } else {
-            run(self.unix, self.work_dir)
-        }
-    }
-    pub fn run_with_output(self) -> Result<Output> {
-        if cfg!(windows) {
-            run_with_output(self.windows, self.work_dir)
-        } else {
-            run_with_output(self.unix, self.work_dir)
-        }
-    }
-}
-
-pub fn run(cmdline: &str, dir: &str) -> Result<()> {
-    do_run(cmdline, dir, |c| {
-        c.stdout(Stdio::inherit());
-    })
-    .map(|_| ())
-}
-
-pub fn run_with_output(cmdline: &str, dir: &str) -> Result<Output> {
-    do_run(cmdline, dir, |_| {})
-}
-
 pub fn run_rustfmt(mode: Mode) -> Result<()> {
     match Command::new("rustup")
         .args(&["run", TOOLCHAIN, "--", "cargo", "fmt", "--version"])
@@ -79,23 +49,11 @@ pub fn run_rustfmt(mode: Mode) -> Result<()> {
     Ok(())
 }
 
-pub fn install_rustfmt() -> Result<()> {
+fn install_rustfmt() -> Result<()> {
     run(&format!("rustup toolchain install {}", TOOLCHAIN), ".")?;
     run(&format!("rustup component add rustfmt --toolchain {}", TOOLCHAIN), ".")
 }
 
-pub fn install_pre_commit_hook() -> Result<()> {
-    let result_path =
-        PathBuf::from(format!("./.git/hooks/pre-commit{}", std::env::consts::EXE_SUFFIX));
-    if !result_path.exists() {
-        let me = std::env::current_exe()?;
-        fs::copy(me, result_path)?;
-    } else {
-        Err(IoError::new(ErrorKind::AlreadyExists, "Git hook already created"))?;
-    }
-    Ok(())
-}
-
 pub fn run_clippy() -> Result<()> {
     match Command::new("rustup")
         .args(&["run", TOOLCHAIN, "--", "cargo", "clippy", "--version"])
@@ -125,7 +83,7 @@ pub fn run_clippy() -> Result<()> {
     Ok(())
 }
 
-pub fn install_clippy() -> Result<()> {
+fn install_clippy() -> Result<()> {
     run(&format!("rustup toolchain install {}", TOOLCHAIN), ".")?;
     run(&format!("rustup component add clippy --toolchain {}", TOOLCHAIN), ".")
 }
@@ -144,41 +102,40 @@ pub fn run_fuzzer() -> Result<()> {
     run("rustup run nightly -- cargo fuzz run parser", "./crates/ra_syntax")
 }
 
-pub fn reformat_staged_files() -> Result<()> {
-    run_rustfmt(Mode::Overwrite)?;
-    let root = project_root();
-    let output = Command::new("git")
-        .arg("diff")
-        .arg("--diff-filter=MAR")
-        .arg("--name-only")
-        .arg("--cached")
-        .current_dir(&root)
-        .output()?;
-    if !output.status.success() {
-        anyhow::bail!(
-            "`git diff --diff-filter=MAR --name-only --cached` exited with {}",
-            output.status
-        );
+/// Cleans the `./target` dir after the build such that only
+/// dependencies are cached on CI.
+pub fn run_pre_cache() -> Result<()> {
+    let slow_tests_cookie = Path::new("./target/.slow_tests_cookie");
+    if !slow_tests_cookie.exists() {
+        panic!("slow tests were skipped on CI!")
     }
-    for line in String::from_utf8(output.stdout)?.lines() {
-        run(&format!("git update-index --add {}", root.join(line).to_string_lossy()), ".")?;
+    rm_rf(slow_tests_cookie)?;
+
+    for entry in Path::new("./target/debug").read_dir()? {
+        let entry = entry?;
+        if entry.file_type().map(|it| it.is_file()).ok() == Some(true) {
+            // Can't delete yourself on windows :-(
+            if !entry.path().ends_with("xtask.exe") {
+                rm_rf(&entry.path())?
+            }
+        }
+    }
+
+    fs::remove_file("./target/.rustc_info.json")?;
+    let to_delete = ["ra_", "heavy_test"];
+    for &dir in ["./target/debug/deps", "target/debug/.fingerprint"].iter() {
+        for entry in Path::new(dir).read_dir()? {
+            let entry = entry?;
+            if to_delete.iter().any(|&it| entry.path().display().to_string().contains(it)) {
+                rm_rf(&entry.path())?
+            }
+        }
     }
+
     Ok(())
 }
 
-fn do_run<F>(cmdline: &str, dir: &str, mut f: F) -> Result<Output>
-where
-    F: FnMut(&mut Command),
-{
-    eprintln!("\nwill run: {}", cmdline);
-    let proj_dir = project_root().join(dir);
-    let mut args = cmdline.split_whitespace();
-    let exec = args.next().unwrap();
-    let mut cmd = Command::new(exec);
-    f(cmd.args(args).current_dir(proj_dir).stderr(Stdio::inherit()));
-    let output = cmd.output().with_context(|| format!("running `{}`", cmdline))?;
-    if !output.status.success() {
-        anyhow::bail!("`{}` exited with {}", cmdline, output.status);
-    }
-    Ok(output)
+fn rm_rf(path: &Path) -> Result<()> {
+    if path.is_file() { fs::remove_file(path) } else { fs::remove_dir_all(path) }
+        .with_context(|| format!("failed to remove {:?}", path))
 }
diff --git a/xtask/src/main.rs b/xtask/src/main.rs
index 9cefad925..053453e6e 100644
--- a/xtask/src/main.rs
+++ b/xtask/src/main.rs
@@ -7,272 +7,109 @@
 //!
 //! This binary is integrated into the `cargo` command line by using an alias in
 //! `.cargo/config`.
-mod help;
 
-use std::{env, fmt::Write, path::PathBuf, str};
+use std::env;
 
-use anyhow::Context;
 use pico_args::Arguments;
 use xtask::{
     codegen::{self, Mode},
-    install_pre_commit_hook, reformat_staged_files, run, run_clippy, run_fuzzer, run_rustfmt,
-    run_with_output, Cmd, Result,
+    install::{ClientOpt, InstallCmd, ServerOpt},
+    pre_commit, run_clippy, run_fuzzer, run_pre_cache, run_rustfmt, Result,
 };
 
-// Latest stable, feel free to send a PR if this lags behind.
-const REQUIRED_RUST_VERSION: u32 = 40;
-
-struct InstallOpt {
-    client: Option<ClientOpt>,
-    server: Option<ServerOpt>,
-}
-
-enum ClientOpt {
-    VsCode,
-}
-
-struct ServerOpt {
-    jemalloc: bool,
-}
-
 fn main() -> Result<()> {
     if env::args().next().map(|it| it.contains("pre-commit")) == Some(true) {
-        return reformat_staged_files();
+        return pre_commit::run_hook();
     }
 
-    let subcommand = match std::env::args_os().nth(1) {
-        None => {
-            eprintln!("{}", help::GLOBAL_HELP);
-            return Ok(());
-        }
-        Some(s) => s,
-    };
-    let mut matches = Arguments::from_vec(std::env::args_os().skip(2).collect());
-    let subcommand = &*subcommand.to_string_lossy();
-    match subcommand {
+    let subcommand = std::env::args().nth(1).unwrap_or_default();
+    let mut args = Arguments::from_vec(std::env::args_os().skip(2).collect());
+
+    match subcommand.as_str() {
         "install" => {
-            if matches.contains(["-h", "--help"]) {
-                eprintln!("{}", help::INSTALL_HELP);
+            if args.contains(["-h", "--help"]) {
+                eprintln!(
+                    "\
+cargo xtask install
+Install rust-analyzer server or editor plugin.
+
+USAGE:
+    cargo xtask install [FLAGS]
+
+FLAGS:
+        --client-code    Install only VS Code plugin
+        --server         Install only the language server
+        --jemalloc       Use jemalloc for server
+    -h, --help           Prints help information
+        "
+                );
                 return Ok(());
             }
-            let server = matches.contains("--server");
-            let client_code = matches.contains("--client-code");
+            let server = args.contains("--server");
+            let client_code = args.contains("--client-code");
             if server && client_code {
-                eprintln!("{}", help::INSTALL_RA_CONFLICT);
+                eprintln!(
+                    "error: The argument `--server` cannot be used with `--client-code`\n\n\
+                     For more information try --help"
+                );
                 return Ok(());
             }
-            let jemalloc = matches.contains("--jemalloc");
-            matches.finish().or_else(handle_extra_flags)?;
-            let opts = InstallOpt {
+
+            let jemalloc = args.contains("--jemalloc");
+
+            args.finish()?;
+
+            InstallCmd {
                 client: if server { None } else { Some(ClientOpt::VsCode) },
                 server: if client_code { None } else { Some(ServerOpt { jemalloc }) },
-            };
-            install(opts)?
+            }
+            .run()
         }
         "codegen" => {
-            if matches.contains(["-h", "--help"]) {
-                help::print_no_param_subcommand_help(&subcommand);
-                return Ok(());
-            }
+            args.finish()?;
             codegen::generate_syntax(Mode::Overwrite)?;
             codegen::generate_parser_tests(Mode::Overwrite)?;
             codegen::generate_assists_docs(Mode::Overwrite)?;
+            Ok(())
         }
         "format" => {
-            if matches.contains(["-h", "--help"]) {
-                help::print_no_param_subcommand_help(&subcommand);
-                return Ok(());
-            }
-            run_rustfmt(Mode::Overwrite)?
+            args.finish()?;
+            run_rustfmt(Mode::Overwrite)
         }
         "install-pre-commit-hook" => {
-            if matches.contains(["-h", "--help"]) {
-                help::print_no_param_subcommand_help(&subcommand);
-                return Ok(());
-            }
-            install_pre_commit_hook()?
+            args.finish()?;
+            pre_commit::install_hook()
         }
         "lint" => {
-            if matches.contains(["-h", "--help"]) {
-                help::print_no_param_subcommand_help(&subcommand);
-                return Ok(());
-            }
-            run_clippy()?
+            args.finish()?;
+            run_clippy()
         }
         "fuzz-tests" => {
-            if matches.contains(["-h", "--help"]) {
-                help::print_no_param_subcommand_help(&subcommand);
-                return Ok(());
-            }
-            run_fuzzer()?
+            args.finish()?;
+            run_fuzzer()
         }
-        _ => eprintln!("{}", help::GLOBAL_HELP),
-    }
-    Ok(())
-}
-
-fn handle_extra_flags(e: pico_args::Error) -> Result<()> {
-    if let pico_args::Error::UnusedArgsLeft(flags) = e {
-        let mut invalid_flags = String::new();
-        for flag in flags {
-            write!(&mut invalid_flags, "{}, ", flag)?;
-        }
-        let (invalid_flags, _) = invalid_flags.split_at(invalid_flags.len() - 2);
-        anyhow::bail!("Invalid flags: {}", invalid_flags)
-    } else {
-        anyhow::bail!(e.to_string())
-    }
-}
-
-fn install(opts: InstallOpt) -> Result<()> {
-    if cfg!(target_os = "macos") {
-        fix_path_for_mac().context("Fix path for mac")?
-    }
-    if let Some(server) = opts.server {
-        install_server(server).context("install server")?;
-    }
-    if let Some(client) = opts.client {
-        install_client(client).context("install client")?;
-    }
-    Ok(())
-}
-
-fn fix_path_for_mac() -> Result<()> {
-    let mut vscode_path: Vec<PathBuf> = {
-        const COMMON_APP_PATH: &str =
-            r"/Applications/Visual Studio Code.app/Contents/Resources/app/bin";
-        const ROOT_DIR: &str = "";
-        let home_dir = match env::var("HOME") {
-            Ok(home) => home,
-            Err(e) => anyhow::bail!("Failed getting HOME from environment with error: {}.", e),
-        };
-
-        [ROOT_DIR, &home_dir]
-            .iter()
-            .map(|dir| String::from(*dir) + COMMON_APP_PATH)
-            .map(PathBuf::from)
-            .filter(|path| path.exists())
-            .collect()
-    };
-
-    if !vscode_path.is_empty() {
-        let vars = match env::var_os("PATH") {
-            Some(path) => path,
-            None => anyhow::bail!("Could not get PATH variable from env."),
-        };
-
-        let mut paths = env::split_paths(&vars).collect::<Vec<_>>();
-        paths.append(&mut vscode_path);
-        let new_paths = env::join_paths(paths).context("build env PATH")?;
-        env::set_var("PATH", &new_paths);
-    }
-
-    Ok(())
-}
-
-fn install_client(ClientOpt::VsCode: ClientOpt) -> Result<()> {
-    let npm_version = Cmd {
-        unix: r"npm --version",
-        windows: r"cmd.exe /c npm --version",
-        work_dir: "./editors/code",
-    }
-    .run();
-
-    if npm_version.is_err() {
-        eprintln!("\nERROR: `npm --version` failed, `npm` is required to build the VS Code plugin")
-    }
-
-    Cmd { unix: r"npm install", windows: r"cmd.exe /c npm install", work_dir: "./editors/code" }
-        .run()?;
-    Cmd {
-        unix: r"npm run package --scripts-prepend-node-path",
-        windows: r"cmd.exe /c npm run package",
-        work_dir: "./editors/code",
-    }
-    .run()?;
-
-    let code_binary = ["code", "code-insiders", "codium"].iter().find(|bin| {
-        Cmd {
-            unix: &format!("{} --version", bin),
-            windows: &format!("cmd.exe /c {}.cmd --version", bin),
-            work_dir: "./editors/code",
+        "pre-cache" => {
+            args.finish()?;
+            run_pre_cache()
         }
-        .run()
-        .is_ok()
-    });
-
-    let code_binary = match code_binary {
-        Some(it) => it,
-        None => anyhow::bail!("Can't execute `code --version`. Perhaps it is not in $PATH?"),
-    };
-
-    Cmd {
-        unix: &format!(r"{} --install-extension ./ra-lsp-0.0.1.vsix --force", code_binary),
-        windows: &format!(
-            r"cmd.exe /c {}.cmd --install-extension ./ra-lsp-0.0.1.vsix --force",
-            code_binary
-        ),
-        work_dir: "./editors/code",
-    }
-    .run()?;
-
-    let output = Cmd {
-        unix: &format!(r"{} --list-extensions", code_binary),
-        windows: &format!(r"cmd.exe /c {}.cmd --list-extensions", code_binary),
-        work_dir: ".",
-    }
-    .run_with_output()?;
-
-    if !str::from_utf8(&output.stdout)?.contains("ra-lsp") {
-        anyhow::bail!(
-            "Could not install the Visual Studio Code extension. \
-             Please make sure you have at least NodeJS 10.x together with the latest version of VS Code installed and try again."
-        );
-    }
-
-    Ok(())
-}
-
-fn install_server(opts: ServerOpt) -> Result<()> {
-    let mut old_rust = false;
-    if let Ok(output) = run_with_output("cargo --version", ".") {
-        if let Ok(stdout) = String::from_utf8(output.stdout) {
-            println!("{}", stdout);
-            if !check_version(&stdout, REQUIRED_RUST_VERSION) {
-                old_rust = true;
-            }
+        _ => {
+            eprintln!(
+                "\
+cargo xtask
+Run custom build command.
+
+USAGE:
+    cargo xtask <SUBCOMMAND>
+
+SUBCOMMANDS:
+    format
+    install-pre-commit-hook
+    fuzz-tests
+    codegen
+    install
+    lint"
+            );
+            Ok(())
         }
     }
-
-    if old_rust {
-        eprintln!(
-            "\nWARNING: at least rust 1.{}.0 is required to compile rust-analyzer\n",
-            REQUIRED_RUST_VERSION,
-        )
-    }
-
-    let res = if opts.jemalloc {
-        run("cargo install --path crates/ra_lsp_server --locked --force --features jemalloc", ".")
-    } else {
-        run("cargo install --path crates/ra_lsp_server --locked --force", ".")
-    };
-
-    if res.is_err() && old_rust {
-        eprintln!(
-            "\nWARNING: at least rust 1.{}.0 is required to compile rust-analyzer\n",
-            REQUIRED_RUST_VERSION,
-        )
-    }
-
-    res
-}
-
-fn check_version(version_output: &str, min_minor_version: u32) -> bool {
-    // Parse second the number out of
-    //      cargo 1.39.0-beta (1c6ec66d5 2019-09-30)
-    let minor: Option<u32> = version_output.split('.').nth(1).and_then(|it| it.parse().ok());
-    match minor {
-        None => true,
-        Some(minor) => minor >= min_minor_version,
-    }
 }
diff --git a/xtask/src/pre_commit.rs b/xtask/src/pre_commit.rs
new file mode 100644
index 000000000..88e868ca6
--- /dev/null
+++ b/xtask/src/pre_commit.rs
@@ -0,0 +1,36 @@
+//! pre-commit hook for code formatting.
+
+use std::{fs, path::PathBuf};
+
+use anyhow::{bail, Result};
+
+use crate::{cmd::run_with_output, project_root, run, run_rustfmt, Mode};
+
+// FIXME: if there are changed `.ts` files, also reformat TypeScript (by
+// shelling out to `npm fmt`).
+pub fn run_hook() -> Result<()> {
+    run_rustfmt(Mode::Overwrite)?;
+
+    let diff = run_with_output("git diff --diff-filter=MAR --name-only --cached", ".")?;
+
+    let root = project_root();
+    for line in String::from_utf8(diff.stdout)?.lines() {
+        run(&format!("git update-index --add {}", root.join(line).to_string_lossy()), ".")?;
+    }
+
+    Ok(())
+}
+
+pub fn install_hook() -> Result<()> {
+    let hook_path: PathBuf =
+        format!("./.git/hooks/pre-commit{}", std::env::consts::EXE_SUFFIX).into();
+
+    if hook_path.exists() {
+        bail!("Git hook already created");
+    }
+
+    let me = std::env::current_exe()?;
+    fs::copy(me, hook_path)?;
+
+    Ok(())
+}