From 21fba447a130a18ac2ca43fc3dd01995bcb13fb6 Mon Sep 17 00:00:00 2001
From: Caleb Owens <caleb@gitbutler.com>
Date: Wed, 5 Feb 2025 12:08:41 +0100
Subject: [PATCH] but-rebase stub

---
 Cargo.lock                   | 12 +++++
 Cargo.toml                   |  1 +
 crates/but-rebase/Cargo.toml | 26 +++++++++++
 crates/but-rebase/src/lib.rs | 90 ++++++++++++++++++++++++++++++++++++
 4 files changed, 129 insertions(+)
 create mode 100644 crates/but-rebase/Cargo.toml
 create mode 100644 crates/but-rebase/src/lib.rs

diff --git a/Cargo.lock b/Cargo.lock
index 71d52bab9c..d94662279a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -720,6 +720,18 @@ dependencies = [
  "serde_json",
 ]
 
+[[package]]
+name = "but-rebase"
+version = "0.0.0"
+dependencies = [
+ "anyhow",
+ "bstr",
+ "gix",
+ "gix-testtools",
+ "insta",
+ "tracing",
+]
+
 [[package]]
 name = "but-workspace"
 version = "0.0.0"
diff --git a/Cargo.toml b/Cargo.toml
index ef81fd8b58..f36c8e1ed3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -71,6 +71,7 @@ but-debugging = { path = "crates/but-debugging" }
 but-core = { path = "crates/but-core" }
 but-workspace = { path = "crates/but-workspace" }
 but-hunk-dependency = { path = "crates/but-hunk-dependency" }
+but-rebase = { path = "crates/but-rebase" }
 
 [profile.release]
 codegen-units = 1 # Compile crates one after another so the compiler can optimize better
diff --git a/crates/but-rebase/Cargo.toml b/crates/but-rebase/Cargo.toml
new file mode 100644
index 0000000000..d8483a3c52
--- /dev/null
+++ b/crates/but-rebase/Cargo.toml
@@ -0,0 +1,26 @@
+[package]
+name = "but-rebase"
+version = "0.0.0"
+edition = "2021"
+authors = ["GitButler <gitbutler@gitbutler.com>"]
+publish = false
+
+[lib]
+doctest = false
+
+[dependencies]
+bstr.workspace = true
+tracing.workspace = true
+anyhow = "1.0.95"
+gix = { workspace = true, features = [
+    "dirwalk",
+    "credentials",
+    "parallel",
+    "serde",
+    "status",
+] }
+
+[dev-dependencies]
+gix-testtools.workspace = true
+gix = { workspace = true, features = ["revision"] }
+insta.workspace = true
diff --git a/crates/but-rebase/src/lib.rs b/crates/but-rebase/src/lib.rs
new file mode 100644
index 0000000000..2a169eccc4
--- /dev/null
+++ b/crates/but-rebase/src/lib.rs
@@ -0,0 +1,90 @@
+#![deny(missing_docs, rust_2018_idioms)]
+//! Rebase for your flying but.
+
+use anyhow::Result;
+use bstr::{BStr, BString};
+
+#[derive(Debug)]
+/// A step to be taken as part of rebase.
+pub enum Step<'a> {
+    /// Reference updates the given reference to the commit beneath it.
+    ///
+    /// Should be a full reference identifer, IE: refs/heads/foo
+    Reference(&'a BStr),
+    /// Picks a commit and squashes it into the commit beneath it.
+    ///
+    /// If a name is provided, it will be used as the new commit's title.
+    /// Otherwise, the commit's title that is getting picked will be taken.
+    ///
+    /// TODO: ADD A VALIDATION STEP FOR THIS
+    /// Must never be the first operation.
+    /// Must never come after a Reference operation.
+    Ammend(gix::ObjectId, Option<&'a BStr>),
+    /// Picks a commit
+    ///
+    /// If a name is provided, it will be used as the new commit's title.
+    /// Otherwise, the commit's title that is getting picked will be taken.
+    Pick(gix::ObjectId, Option<&'a BStr>),
+    /// Merges in a commit and it's parents
+    ///
+    /// The name provided will be used as the merge commit's name
+    Merge(gix::ObjectId, &'a BStr),
+}
+
+// vec![
+//      Step::Pick(fdsaadfs),
+//      Step::Pick(fdsaadfs),
+//      Step::Ammend(fdsaadfs),
+//      Step::Reference("refs/heads/foo"),
+// ]
+
+fn but_base(base: gix::ObjectId, steps: &[Step]) -> Result<RebaseOutput> {
+    let mut references = vec![];
+    let mut commits = vec![];
+
+    for step in steps {
+        match step {
+            Step::Reference(refname) => references.push(Reference {
+                name: refname.to_owned().into(),
+                oid: commits.last().unwrap_or(&base).to_owned(),
+            }),
+            Step::Pick(to_pick, commit_name) => {
+                let target_commit = commits.last().unwrap_or(&base).to_owned();
+                let result = cherry_rebase_group(todo!(), target_commit, &[to_pick], true)?;
+                commits.push(result)
+            }
+            Step::Ammend(to_pick, commit_name) => {
+                let target_commit = commits
+                    .last()
+                    .expect("Ammend should never be the first operation");
+                let result = cherry_rebase_group(todo!(), target_commit, &[to_pick], true)?;
+                commits.pop(); // Remove the commit that we ammended
+                commits.push(result)
+            }
+            Step::Merge(to_merge, commit_name) => {
+                // Do the same with gitbutler_merge_commits
+            }
+        }
+    }
+
+    Ok(RebaseOutput {
+        references,
+        commits,
+    })
+}
+
+/// Describes a reference
+pub struct Reference {
+    /// The reference identifier, IE: refs/heads/foo
+    name: BString,
+    /// The oid that the reference points to.
+    oid: gix::ObjectId,
+}
+
+/// The result of a rebase
+pub struct RebaseOutput {
+    /// The references, from child-most to parent-most.
+    references: Vec<Reference>,
+    /// The commits, from child-most to parent-most.
+    commits: Vec<gix::ObjectId>,
+}