fix: attempt to include .git in cross-rs build ctx

bolt-sidecar/Cross.toml

@@ -9,3 +9,8 @@ pre-build = [
     # more info at: https://github.com/cross-rs/cross/issues/1565#issuecomment-2483968180
     "apt-get --assume-yes --no-install-recommends install gcc-10 g++-10 && ln -sf /usr/bin/gcc-10 /usr/bin/gcc && ln -sf /usr/bin/g++-10 /usr/bin/g++"
 ]
+
+[build.env]
+volumes = [
+    "GIT_DIR=./../.git"
+]

bolt-sidecar/build.rs

@@ -1,3 +1,15 @@
 fn main() {
+    // Built uses the `MANIFEST_DIR` environment variable to find the location of `Cargo.toml` and
+    // `.git`. When building from PWD=$BOLT_REPO/bolt-sidecar, the `.git` directory won't be
+    // found, therefore the git commit info will be missing from the build-time information.
+    //
+    // To work around this, we also attempt to read the commit hash from the `.git/FETCH_HEAD` file
+    // and make it available as an environment variable at runtime.
+
+    // make the commit hash available as an environment variable at runtime
+    if let Ok(commit_hash) = std::fs::read_to_string("../.git/FETCH_HEAD") {
+        println!("cargo:rustc-env=GIT_COMMIT_HASH={}", commit_hash.trim());
+    }
+
     built::write_built_file().expect("Failed to acquire build-time information");
 }

bolt-sidecar/src/common/mod.rs

@@ -1,5 +1,7 @@
 use lazy_static::lazy_static;
 
+use crate::built_info;
+
 /// Utilities for retrying a future with backoff.
 pub mod backoff;
 
@@ -14,6 +16,21 @@ pub mod transactions;
 
 lazy_static! {
     /// The version of the Bolt sidecar binary.
-    pub static ref BOLT_SIDECAR_VERSION: String =
-        format!("v{}-{}", env!("CARGO_PKG_VERSION"), crate::built_info::GIT_COMMIT_HASH_SHORT.unwrap_or("unknown"));
+    ///
+    /// Example format: "v0.1.0-alpha-abcdefg"
+    pub static ref BOLT_SIDECAR_VERSION: String = format!(
+        "v{}{}",
+        built_info::PKG_VERSION,
+        // Include the git commit hash, if available
+        built_info::GIT_COMMIT_HASH_SHORT.map(|s| format!("-{}", s)).unwrap_or_else(|| {
+            // If built info is not available, try the environment variable
+            let from_env = std::env::var("GIT_COMMIT_HASH").map(|s| {
+                // take only the first 7 characters of the full hash
+                format!("-{}", s.chars().take(7).collect::<String>())
+            });
+
+            // If the environment variable is not set either, return an empty string
+            from_env.unwrap_or_default()
+        })
+    );
 }