cli version: Show UTC date as part of the version next to the commi…

…t id

The date comes from the commiter date of the commit. This is so that
it's easy to tell at a glance how old a version is.

To make it easier to get UTC date, we first obtain it as a Unix
timestamp, which should always be UTC. This will make the
interaction with Nix in a subsequent commit easier.

cli/Cargo.toml

@@ -28,6 +28,7 @@ required-features = ["test-fakes"]
 
 [build-dependencies]
 cargo_metadata = { workspace = true }
+chrono = { workspace = true }
 
 [dependencies]
 chrono = { workspace = true }

cli/build.rs

@@ -12,11 +12,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+extern crate chrono;
+
 use std::path::Path;
 use std::process::Command;
 use std::str;
 
 use cargo_metadata::MetadataCommand;
+use chrono::prelude::*;
 
 const GIT_HEAD_PATH: &str = "../.git/HEAD";
 const JJ_OP_HEADS_PATH: &str = "../.jj/repo/op_heads/heads";
@@ -41,21 +44,44 @@ fn main() -> std::io::Result<()> {
     }
     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);
+    // TODO: timestamp can be "nix"
+    if let Some((maybe_date, git_hash)) = get_git_timestamp_and_hash() {
+        println!(
+            "cargo:rustc-env=JJ_VERSION={}-{}-{}",
+            version,
+            maybe_date
+                .map(|d| d.format("%Y%m%d").to_string())
+                .unwrap_or_else(|| "dateunknown".to_string()),
+            git_hash
+        );
     } else {
         println!("cargo:rustc-env=JJ_VERSION={}", version);
     }
 
     Ok(())
 }
 
-fn get_git_hash() -> Option<String> {
+/// Convert a string with a unix timestamp to a date
+fn timestamp_to_date(ts_str: &str) -> Option<DateTime<Utc>> {
+    ts_str
+        .parse::<i64>()
+        .ok()
+        .and_then(|ts| DateTime::<Utc>::from_timestamp(ts, 0))
+}
+
+/// Return the UTC committer date (maybe) and the git hash
+fn get_git_timestamp_and_hash() -> Option<(Option<DateTime<Utc>>, String)> {
     if let Some(nix_hash) = std::env::var("NIX_JJ_GIT_HASH")
         .ok()
         .filter(|s| !s.is_empty())
     {
-        return Some(nix_hash);
+        return Some((None, nix_hash));
+    }
+
+    fn parse_timestamp_vbar_hash(bytes: &[u8]) -> (Option<DateTime<Utc>>, String) {
+        let s = str::from_utf8(bytes).unwrap().trim_end();
+        let (ts_str, id) = s.split_once('|').unwrap();
+        (timestamp_to_date(ts_str), id.to_owned())
     }
     if let Ok(output) = Command::new("jj")
         .args([
@@ -64,19 +90,21 @@ fn get_git_hash() -> Option<String> {
             "log",
             "--no-graph",
             "-r=@-",
-            "-T=commit_id",
+            r#"-T=committer.timestamp().utc().format("%s") ++ "|" ++ commit_id"#,
         ])
         .output()
     {
         if output.status.success() {
-            return Some(String::from_utf8(output.stdout).unwrap());
+            return Some(parse_timestamp_vbar_hash(&output.stdout));
         }
     }
 
-    if let Ok(output) = Command::new("git").args(["rev-parse", "HEAD"]).output() {
+    if let Ok(output) = Command::new("git")
+        .args(["log", "-1", "--format=%ct|%H", "HEAD"])
+        .output()
+    {
         if output.status.success() {
-            let line = str::from_utf8(&output.stdout).unwrap();
-            return Some(line.trim_end().to_owned());
+            return Some(parse_timestamp_vbar_hash(&output.stdout));
         }
     }
 

cli/tests/test_global_opts.rs

@@ -14,6 +14,8 @@
 
 use std::ffi::OsString;
 
+use assert_matches::assert_matches;
+
 use crate::common::{get_stderr_string, TestEnvironment};
 
 pub mod common;
@@ -67,10 +69,12 @@ fn test_no_subcommand() {
 
     let stdout = test_env.jj_cmd_success(test_env.env_root(), &["--version"]);
     let sanitized = stdout.replace(|c: char| c.is_ascii_hexdigit(), "?");
-    assert!(
-        sanitized == "jj ?.??.?\n"
-            || sanitized == "jj ?.??.?-????????????????????????????????????????\n",
-        "{sanitized}"
+    assert_matches!(
+        sanitized.as_str(),
+        "jj ?.??.?\n"
+            | "jj ?.??.?-????????-????????????????????????????????????????\n"
+            // `dateunknown` turns into `??t?unknown` since d,a,e are hex digits.
+            | "jj ?.??.?-??t?unknown-????????????????????????????????????????\n"
     );
 
     let stdout = test_env.jj_cmd_success(test_env.env_root(), &["-R", "repo"]);