From 22976d9607f2510d7e6fb4488cc8da466fd11149 Mon Sep 17 00:00:00 2001
From: Jason Gross <jgross@mit.edu>
Date: Wed, 23 Oct 2024 20:47:45 -0700
Subject: [PATCH] Add setup-alternates for less git storage usage

---
 etc/setup-alternates.py | 89 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100755 etc/setup-alternates.py

diff --git a/etc/setup-alternates.py b/etc/setup-alternates.py
new file mode 100755
index 00000000..41410f2f
--- /dev/null
+++ b/etc/setup-alternates.py
@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+# %%
+import os
+import subprocess
+from pathlib import Path
+
+
+def get_git_dir(submodule_path: str | Path) -> Path | None:
+    """Gets the actual .git directory for a submodule."""
+    git_dir_file = Path(submodule_path) / ".git"
+    if git_dir_file.is_file():
+        with git_dir_file.open("r") as f:
+            git_dir_relative = f.read().strip().split(": ")[1]
+        git_dir = Path(submodule_path) / git_dir_relative
+        return git_dir.resolve()
+    return None
+
+
+def check_max_of_4_in_git_dir(git_dir: str | Path) -> bool:
+    """Checks if 'max_of_4.py' is in the GIT_DIR path."""
+    return "max_of_4.py" in str(git_dir)
+
+
+def get_alternates_file(git_dir: str | Path) -> Path | None:
+    """Returns the path to the alternates file, or None if it does not exist."""
+    return Path(git_dir) / "objects" / "info" / "alternates"
+
+
+def get_relative_path(submodule_path: str | Path, target_path: str | Path) -> Path:
+    """Calculates the relative path from the submodule's root directory to the target path."""
+    submodule_path = Path(submodule_path).resolve()
+    target_path = Path(target_path).resolve()
+    return Path(os.path.relpath(target_path, submodule_path))
+
+
+def get_repo_root() -> Path:
+    """Returns the root directory of the git repository."""
+    # Run the git command to get the top-level directory
+    result = subprocess.run(
+        ["git", "rev-parse", "--show-toplevel"],
+        capture_output=True,
+        text=True,
+        check=True,
+    )
+    # Return the path as a Path object
+    return Path(result.stdout.strip())
+
+
+def process_submodules():
+    """Processes each submodule and checks for max_of_4.py, alternates, and relative paths."""
+    # Use git submodule foreach to get the list of submodules
+    os.chdir(get_repo_root())
+    result = subprocess.run(
+        ["git", "submodule", "foreach", "--quiet", "echo $path"],
+        capture_output=True,
+        text=True,
+        check=True,
+    )
+    submodules = result.stdout.strip().splitlines()
+
+    for submodule in submodules:
+        print(f"Checking submodule: {submodule}")
+
+        # Get the actual git directory for the submodule
+        git_dir = get_git_dir(submodule)
+        if git_dir is None:
+            print(f"Could not find .git directory for submodule: {submodule}")
+            continue
+
+        # Check if 'max_of_4.py' is in the GIT_DIR path
+        if not check_max_of_4_in_git_dir(git_dir):
+            print(f"max_of_4.py not found in GIT_DIR: {git_dir}")
+
+            # Check for the alternates file
+            alternates_file = get_alternates_file(git_dir)
+            print(f"Alternates file found at: {alternates_file}")
+
+            # Calculate the relative path to max_of_4.py/objects using pathlib
+            relative_target = ".git/modules/notebooks_jason/.cache/max_of_4.py/objects"
+            print(f"Finding get_relative_path({alternates_file.parent.parent}, {relative_target})")
+            relative_path = get_relative_path(alternates_file.parent.parent, relative_target)
+            print(f"Relative path to alternates: {relative_path}")
+            alternates_file.write_text(str(relative_path))
+        else:
+            print("max_of_4.py is already in the GIT_DIR path")
+
+
+if __name__ == "__main__":
+    process_submodules()