make gitoxide publishable again

Apparently build scripts aren't executed when verifying a package, and this
change should get past that.

Author: Byron

Diff for: src/plumbing/main.rs

@@ -149,7 +149,9 @@ pub fn main() -> Result<()> {
                     let mut engine = core::corpus::Engine::open_or_create(
                         db,
                         core::corpus::engine::State {
-                            gitoxide_version: env!("GITOXIDE_VERSION").into(),
+                            gitoxide_version: option_env!("GITOXIDE_VERSION")
+                                .ok_or_else(|| anyhow::anyhow!("GITOXIDE_VERSION must be set in build-script"))?
+                                .into(),
                             progress,
                             trace_to_progress: trace,
                             reverse_trace_lines,

Diff for: src/plumbing/options/mod.rs

@@ -4,7 +4,7 @@ use gitoxide_core as core;
 use gix::bstr::BString;
 
 #[derive(Debug, clap::Parser)]
-#[clap(name = "gix", about = "The git underworld", version = env!("GITOXIDE_VERSION"))]
+#[clap(name = "gix", about = "The git underworld", version = option_env!("GITOXIDE_VERSION"))]
 #[clap(subcommand_required = true)]
 #[clap(arg_required_else_help = true)]
 pub struct Args {

Diff for: src/porcelain/options.rs

@@ -1,7 +1,7 @@
 use std::path::PathBuf;
 
 #[derive(Debug, clap::Parser)]
-#[clap(about = "The rusty git", version = env!("GITOXIDE_VERSION"))]
+#[clap(about = "The rusty git", version = option_env!("GITOXIDE_VERSION"))]
 #[clap(subcommand_required = true)]
 pub struct Args {
     /// Do not display verbose messages and progress information