From 886289f98003f935d774a40f6db746ae70649936 Mon Sep 17 00:00:00 2001
From: Sebastian Thiel <sebastian.thiel@icloud.com>
Date: Tue, 17 Oct 2023 09:22:26 +0200
Subject: [PATCH] feat: add `gix free discover` to inform about repository
 discovery.

It's mainly to better understand what's causing certain failures
if a repository can't be opened, in different modes of operations.
---
 gitoxide-core/src/discover.rs | 59 +++++++++++++++++++++++++++++++++++
 gitoxide-core/src/lib.rs      |  3 ++
 src/plumbing/main.rs          | 10 ++++++
 src/plumbing/options/free.rs  |  2 ++
 4 files changed, 74 insertions(+)
 create mode 100644 gitoxide-core/src/discover.rs

diff --git a/gitoxide-core/src/discover.rs b/gitoxide-core/src/discover.rs
new file mode 100644
index 00000000000..d1ab7d3d23c
--- /dev/null
+++ b/gitoxide-core/src/discover.rs
@@ -0,0 +1,59 @@
+use std::path::Path;
+
+pub fn discover(repo: &Path, mut out: impl std::io::Write) -> anyhow::Result<()> {
+    let mut has_err = false;
+    writeln!(out, "open (strict) {}:", repo.display())?;
+    has_err |= print_result(
+        &mut out,
+        gix::open_opts(repo, gix::open::Options::default().strict_config(true)),
+    )?;
+
+    if has_err {
+        writeln!(out, "open (lenient) {}:", repo.display())?;
+        has_err |= print_result(
+            &mut out,
+            gix::open_opts(repo, gix::open::Options::default().strict_config(false)),
+        )?;
+    }
+
+    writeln!(out)?;
+    writeln!(out, "discover from {}:", repo.display())?;
+    has_err |= print_result(&mut out, gix::discover(repo))?;
+
+    writeln!(out)?;
+    writeln!(out, "discover (plumbing) from {}:", repo.display())?;
+    has_err |= print_result(&mut out, gix::discover::upwards(repo))?;
+
+    if has_err {
+        writeln!(out)?;
+        anyhow::bail!("At least one operation failed")
+    }
+
+    Ok(())
+}
+
+fn print_result<T, E>(mut out: impl std::io::Write, res: Result<T, E>) -> std::io::Result<bool>
+where
+    T: std::fmt::Debug,
+    E: std::error::Error + Send + Sync + 'static,
+{
+    let mut has_err = false;
+    let to_print = match res {
+        Ok(good) => {
+            format!("{good:#?}")
+        }
+        Err(err) => {
+            has_err = true;
+            format!("{:?}", anyhow::Error::from(err))
+        }
+    };
+    indent(&mut out, to_print)?;
+    Ok(has_err)
+}
+
+fn indent(mut out: impl std::io::Write, msg: impl Into<String>) -> std::io::Result<()> {
+    for line in msg.into().lines() {
+        writeln!(out, "\t{line}")?;
+    }
+    Ok(())
+}
diff --git a/gitoxide-core/src/lib.rs b/gitoxide-core/src/lib.rs
index 58e688ea983..b4dc9da5365 100644
--- a/gitoxide-core/src/lib.rs
+++ b/gitoxide-core/src/lib.rs
@@ -79,5 +79,8 @@ pub mod pack;
 pub mod query;
 pub mod repository;
 
+mod discover;
+pub use discover::discover;
+
 #[cfg(all(feature = "async-client", feature = "blocking-client"))]
 compile_error!("Cannot set both 'blocking-client' and 'async-client' features as they are mutually exclusive");
diff --git a/src/plumbing/main.rs b/src/plumbing/main.rs
index 94b085dd85e..677ec60fe0c 100644
--- a/src/plumbing/main.rs
+++ b/src/plumbing/main.rs
@@ -72,6 +72,7 @@ pub fn main() -> Result<()> {
     let object_hash = args.object_hash;
     let config = args.config;
     let repository = args.repository;
+    let repository_path = repository.clone();
     enum Mode {
         Strict,
         StrictWithGitInstallConfig,
@@ -449,6 +450,15 @@ pub fn main() -> Result<()> {
         )
         .map(|_| ()),
         Subcommands::Free(subcommands) => match subcommands {
+            free::Subcommands::Discover => prepare_and_run(
+                "discover",
+                trace,
+                verbose,
+                progress,
+                progress_keep_open,
+                None,
+                move |_progress, out, _err| core::discover(&repository_path, out),
+            ),
             free::Subcommands::CommitGraph(cmd) => match cmd {
                 free::commitgraph::Subcommands::Verify { path, statistics } => prepare_and_run(
                     "commitgraph-verify",
diff --git a/src/plumbing/options/free.rs b/src/plumbing/options/free.rs
index 64aa443d4de..083dd943b34 100644
--- a/src/plumbing/options/free.rs
+++ b/src/plumbing/options/free.rs
@@ -14,6 +14,8 @@ pub enum Subcommands {
     Pack(pack::Subcommands),
     /// Subcommands for interacting with a worktree index, typically at .git/index
     Index(index::Platform),
+    /// Show information about repository discovery and when opening a repository at the current path.
+    Discover,
 }
 
 ///