use a multi-call binary ('uni') to have only one build step (#987)

This increases installation size, but should decrease build time
as symbols and optimizations can be shared more.

Once deduplication of generics has happened, these wins should increase
even more.

However, as it probably increases compile times for CI as it will take longer
to build each binary with different compile time flags. Thus I just leave
the `uni.rs` file for reference.

Cargo.toml

@@ -12,8 +12,8 @@ resolver = "2"
 
 [[bin]]
 name = "ein"
-doc = false
 path = "src/ein.rs"
+doc = false
 test = false
 doctest = false
 

src/gix.rs

@@ -1,7 +1,6 @@
 #![deny(unsafe_code, rust_2018_idioms)]
 
 mod plumbing;
-mod shared;
 
 use anyhow::Result;
 

src/plumbing/main.rs

@@ -13,16 +13,14 @@ use gitoxide_core as core;
 use gitoxide_core::{pack::verify, repository::PathsOrPatterns};
 use gix::bstr::{io::BufReadExt, BString};
 
-use crate::{
-    plumbing::{
-        options::{
-            attributes, commit, commitgraph, config, credential, exclude, free, index, mailmap, odb, revision, tree,
-            Args, Subcommands,
-        },
-        show_progress,
+use crate::plumbing::{
+    options::{
+        attributes, commit, commitgraph, config, credential, exclude, free, index, mailmap, odb, revision, tree, Args,
+        Subcommands,
     },
-    shared::pretty::prepare_and_run,
+    show_progress,
 };
+use gitoxide::shared::pretty::prepare_and_run;
 
 #[cfg(feature = "gitoxide-core-async-client")]
 pub mod async_util {

src/uni.rs

@@ -0,0 +1,28 @@
+//! An experiment to see how a multi-call binary could look like.
+//! For CI this would mean longer compile times though as it rebuilds `gix`
+//! with varying compile flags, which also means that it recompiles all source or `ein`.
+//!
+//! However, doing this could be interesting for distribution if the files are hard-linked
+//! instead of copied, which is why it is left here.
+#![deny(unsafe_code, rust_2018_idioms)]
+
+use anyhow::{bail, Result};
+
+mod plumbing;
+mod porcelain;
+
+#[cfg(feature = "pretty-cli")]
+fn main() -> Result<()> {
+    match std::env::current_exe()?
+        .file_stem()
+        .and_then(|stem| stem.to_str())
+        .unwrap_or("gix")
+    {
+        "gix" => plumbing::main(),
+        "ein" => porcelain::main(),
+        unknown => bail!("Executable named '{unknown}' cannot be launched. Exe must be named either `gix` or `ein`."),
+    }
+}
+
+#[cfg(not(feature = "pretty-cli"))]
+compile_error!("Please set 'pretty-cli' feature flag");