Remove vergen dependency

crates/cli/Cargo.toml

@@ -101,7 +101,7 @@ pretty_assertions.workspace = true
 serial_test.workspace = true
 
 [build-dependencies]
-vergen-gitcl = { version = "1.0.0", features = ["emit_and_set"] }
+chrono = "0.4.26"
 
 [[bench]]
 name = "time_bench"

crates/cli/build.rs

@@ -1,45 +1,59 @@
+use chrono::prelude::*;
 use std::fs;
-use vergen_gitcl::{Emitter, GitclBuilder};
+use std::process::Command;
+use std::str;
 
 fn main() {
-    // Emit git information
-    let git_instructions = GitclBuilder::default()
-        .commit_timestamp(true)
-        .sha(true) // Use shorter commit hash
-        .dirty(true) // Count untracked files as dirty
-        .build()
-        .unwrap();
-    Emitter::default()
-        .add_instructions(&git_instructions)
-        .unwrap()
-        .emit_and_set()
-        .unwrap();
+    // Rebuild if this build.rs file changes
+    println!("cargo:rerun-if-changed=build.rs");
 
-    // Read the version file
+    // The version file is located at the root of the repository
     let version_file_path = "../../version.txt";
+
+    // Rebuild if version file changes
+    println!("cargo:rerun-if-changed={}", version_file_path);
+
+    // Read the version file
     let version_file_contents = fs::read_to_string(version_file_path).unwrap();
 
     // If the version is "built-from-source", replace it with the git commit information
     let version = match version_file_contents.trim() {
         "built-from-source" => {
-            let commit_hash = std::env::var("VERGEN_GIT_SHA").unwrap();
-            let git_dirty_message = match std::env::var("VERGEN_GIT_DIRTY") {
-                Ok(s) => match s.as_str() {
-                    "true" => " with additional changes",
-                    _ => "",
-                },
-                _ => "",
+            // Rebuild if a new Git commit is made
+            println!("cargo:rerun-if-changed=.git/HEAD");
+
+            // Get the hash of the current commit
+            let git_describe_output = Command::new("git")
+                .arg("describe")
+                .arg("--always")
+                .arg("--dirty= with changes") // Add a suffix if the working directory is dirty
+                .output()
+                .expect("Failed to execute git describe command");
+            let git_commit_hash = str::from_utf8(&git_describe_output.stdout)
+                .expect("Failed to parse git describe output")
+                .trim();
+
+            // Get the datetime of the last commit
+            let git_show_output = Command::new("git")
+                .arg("show")
+                .arg("--no-patch")
+                .arg("--format=%ct") // Outputting a UNIX timestamp is the only way to always use UTC
+                .output()
+                .expect("Failed to execute git show command");
+            let git_commit_timestamp = {
+                let timestamp = str::from_utf8(&git_show_output.stdout)
+                    .expect("Failed to parse git show output as a string")
+                    .trim()
+                    .parse::<i64>()
+                    .expect("Failed to parse timestamp as an integer");
+                DateTime::from_timestamp(timestamp, 0)
+                    .expect("Failed to parse timestamp")
+                    .format("%Y-%m-%d %H:%M:%S")
             };
-            let git_commit_timestamp = std::env::var("VERGEN_GIT_COMMIT_TIMESTAMP").unwrap();
-            format!(
-                "built from commit {}{}, committed at {}",
-                commit_hash, git_dirty_message, git_commit_timestamp
-            )
+            format!("built from commit {git_commit_hash}, committed at {git_commit_timestamp}")
         }
         _ => version_file_contents.trim().to_string(),
     };
     // Emit the version to a build-time environment variable
     println!("cargo:rustc-env=ROC_VERSION={}", version);
-    // Rebuild if version.txt changes
-    println!("cargo:rerun-if-changed={}", version_file_path);
 }