Implement git commit hash tracking for build display

- Add get_git_commit() method to read /var/lib/cm-dashboard/git-commit
- Replace NixOS build version with actual git commit hash
- Show deployed commit hash as 'Build:' value for accurate tracking
- Enable verification of which exact commit is deployed per host
- Update version to 0.1.42

agent/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard-agent"
-version = "0.1.41"
+version = "0.1.42"
 edition = "2021"
 
 [dependencies]

agent/src/collectors/nixos.rs

@@ -37,6 +37,22 @@ impl NixOSCollector {
     }
 
     /// Get configuration hash from deployed nix store system
+    /// Get git commit hash from rebuild process
+    fn get_git_commit(&self) -> Result<String, Box<dyn std::error::Error>> {
+        let commit_file = "/var/lib/cm-dashboard/git-commit";
+        match std::fs::read_to_string(commit_file) {
+            Ok(content) => {
+                let commit_hash = content.trim();
+                if commit_hash.len() >= 7 {
+                    Ok(commit_hash.to_string())
+                } else {
+                    Err("Git commit hash too short".into())
+                }
+            }
+            Err(e) => Err(format!("Failed to read git commit file: {}", e).into())
+        }
+    }
+
     fn get_config_hash(&self) -> Result<String, Box<dyn std::error::Error>> {
         // Read the symlink target of /run/current-system to get nix store path
         let output = Command::new("readlink")
@@ -74,25 +90,25 @@ impl Collector for NixOSCollector {
         let mut metrics = Vec::new();
         let timestamp = chrono::Utc::now().timestamp() as u64;
 
-        // Collect NixOS build information (config hash)
-        match self.get_config_hash() {
-            Ok(config_hash) => {
+        // Collect git commit information (shows what's actually deployed)
+        match self.get_git_commit() {
+            Ok(git_commit) => {
                 metrics.push(Metric {
                     name: "system_nixos_build".to_string(),
-                    value: MetricValue::String(config_hash),
+                    value: MetricValue::String(git_commit),
                     unit: None,
-                    description: Some("NixOS deployed configuration hash".to_string()),
+                    description: Some("Git commit hash of deployed configuration".to_string()),
                     status: Status::Ok,
                     timestamp,
                 });
             }
             Err(e) => {
-                debug!("Failed to get config hash: {}", e);
+                debug!("Failed to get git commit: {}", e);
                 metrics.push(Metric {
                     name: "system_nixos_build".to_string(),
                     value: MetricValue::String("unknown".to_string()),
                     unit: None,
-                    description: Some("NixOS config hash (failed to detect)".to_string()),
+                    description: Some("Git commit hash (failed to detect)".to_string()),
                     status: Status::Unknown,
                     timestamp,
                 });

dashboard/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard"
-version = "0.1.41"
+version = "0.1.42"
 edition = "2021"
 
 [dependencies]

dashboard/src/main.rs

@@ -14,7 +14,7 @@ use app::Dashboard;
 
 /// Get hardcoded version
 fn get_version() -> &'static str {
-    "v0.1.41"
+    "v0.1.42"
 }
 
 /// Check if running inside tmux session

shared/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard-shared"
-version = "0.1.41"
+version = "0.1.42"
 edition = "2021"
 
 [dependencies]