Format '--version' calendar version as 'YY.0M'

We use calendar versioning which isn't supported by Cargo, so we need
to add an extra leading zero to the month for releases between January
and September to match our usual 'YY.0M' formatting.

Closes helix-editor#12414

helix-loader/build.rs

@@ -6,14 +6,6 @@ const MAJOR: &str = env!("CARGO_PKG_VERSION_MAJOR");
 const MINOR: &str = env!("CARGO_PKG_VERSION_MINOR");
 const PATCH: &str = env!("CARGO_PKG_VERSION_PATCH");
 
-fn get_calver() -> String {
-    if PATCH == "0" {
-        format!("{MAJOR}.{MINOR}")
-    } else {
-        format!("{MAJOR}.{MINOR}.{PATCH}")
-    }
-}
-
 fn main() {
     let git_hash = Command::new("git")
         .args(["rev-parse", "HEAD"])
@@ -23,7 +15,17 @@ fn main() {
         .and_then(|x| String::from_utf8(x.stdout).ok())
         .or_else(|| option_env!("HELIX_NIX_BUILD_REV").map(|s| s.to_string()));
 
-    let calver = get_calver();
+    let minor = if MINOR.len() == 1 {
+        // Print single-digit months in '0M' format
+        format!("0{MINOR}")
+    } else {
+        MINOR.to_string()
+    };
+    let calver = if PATCH == "0" {
+        format!("{MAJOR}.{minor}")
+    } else {
+        format!("{MAJOR}.{minor}.{PATCH}")
+    };
     let version: Cow<_> = match &git_hash {
         Some(git_hash) => format!("{} ({})", calver, &git_hash[..8]).into(),
         None => calver.into(),