feat: add --version command

Closes #261.

build.rs

@@ -0,0 +1,27 @@
+// Include the GIT_HASH, in `GIT_HASH` environment variable at build
+// time, panic'ing if it can not be found
+//
+// https://stackoverflow.com/questions/43753491/include-git-commit-hash-as-string-into-rust-program
+use std::process::Command;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    println!("cargo:rerun-if-env-changed=GIT_HASH");
+    // Populate env!(GIT_HASH) with the current git commit
+    println!("cargo:rustc-env=GIT_HASH={}", get_git_hash());
+
+    Ok(())
+}
+
+fn get_git_hash() -> String {
+    let git_hash = {
+        let output = Command::new("git")
+            .args(["describe", "--always", "--dirty", "--abbrev=64"])
+            .output()
+            .expect("failed to execute git rev-parse to read the current git hash");
+
+        String::from_utf8(output.stdout).expect("non-utf8 found in git hash")
+    };
+
+    assert!(!git_hash.is_empty(), "attempting to embed empty git hash");
+    git_hash
+}

src/constants.rs

@@ -1,2 +1,10 @@
-pub(crate) static APP_USER_AGENT: &str =
-    concat!(env!("CARGO_PKG_NAME"), "/", env!("CARGO_PKG_VERSION"),);
+pub(crate) static APP_USER_AGENT: &str = concat!(
+    env!("CARGO_PKG_NAME"),
+    "/",
+    env!("CARGO_PKG_VERSION"),
+    ", revision ",
+    env!("GIT_HASH")
+);
+
+pub(crate) static VERSION_STRING: &str =
+    concat!(env!("CARGO_PKG_VERSION"), ", revision ", env!("GIT_HASH"));

src/main.rs

@@ -9,6 +9,7 @@ use crate::{
 };
 use anyhow::{Context, Result};
 use clap::{Parser, Subcommand};
+use constants::VERSION_STRING;
 use folders::Folder;
 use futures::{StreamExt, TryStreamExt};
 use logging::{setup_logging, LoggingCLIConfig};
@@ -40,6 +41,10 @@ mod signal;
 
 /// CLI args.
 #[derive(Debug, Parser)]
+#[command(
+    about = "CLI (Command Line Interface) for Tutanota/Tuta, mostly meant for mass export.",
+    version = VERSION_STRING,
+)]
 struct Args {
     /// Logging config.
     #[clap(flatten)]

tests/cli.rs

@@ -20,6 +20,12 @@ fn test_help_cmd() {
     cmd.arg("help").assert().success();
 }
 
+#[test]
+fn test_version_arg() {
+    let mut cmd = cmd();
+    cmd.arg("--version").assert().success();
+}
+
 fn cmd() -> Command {
     Command::cargo_bin(env!("CARGO_PKG_NAME")).unwrap()
 }