@@ -1,0 +1,121 @@
name: CI
on:
  pull_request:
    branches: [main]
  push:
    branches: [main]
env:
  MIX_ENV: test
  ELIXIR_VERSION: "1.17"
  OTP_VERSION: "27"
jobs:
  compile:
    name: Compile
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: erlef/setup-beam@v1
        with:
          elixir-version: ${{ env.ELIXIR_VERSION }}
          otp-version: ${{ env.OTP_VERSION }}
      - uses: actions/cache@v4
        with:
          path: |
            deps
            _build
          key: ${{ runner.os }}-mix-${{ hashFiles('mix.lock') }}
          restore-keys: ${{ runner.os }}-mix-
      - run: mix deps.get
      - run: mix compile --warnings-as-errors
  test:
    name: Test
    needs: compile
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: erlef/setup-beam@v1
        with:
          elixir-version: ${{ env.ELIXIR_VERSION }}
          otp-version: ${{ env.OTP_VERSION }}
      - uses: actions/cache@v4
        with:
          path: |
            deps
            _build
          key: ${{ runner.os }}-mix-${{ hashFiles('mix.lock') }}
          restore-keys: ${{ runner.os }}-mix-
      - run: mix deps.get
      - run: mix test
  format:
    name: Format
    needs: compile
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: erlef/setup-beam@v1
        with:
          elixir-version: ${{ env.ELIXIR_VERSION }}
          otp-version: ${{ env.OTP_VERSION }}
      - uses: actions/cache@v4
        with:
          path: |
            deps
            _build
          key: ${{ runner.os }}-mix-${{ hashFiles('mix.lock') }}
          restore-keys: ${{ runner.os }}-mix-
      - run: mix deps.get
      - run: mix format --check-formatted
  license:
    name: License Check
    needs: compile
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: erlef/setup-beam@v1
        with:
          elixir-version: ${{ env.ELIXIR_VERSION }}
          otp-version: ${{ env.OTP_VERSION }}
      - uses: actions/cache@v4
        with:
          path: |
            deps
            _build
          key: ${{ runner.os }}-mix-${{ hashFiles('mix.lock') }}
          restore-keys: ${{ runner.os }}-mix-
      - run: mix deps.get
      - run: mix license_check
  dialyzer:
    name: Dialyzer
    needs: compile
    runs-on: ubuntu-latest
    env:
      MIX_ENV: dev
    steps:
      - uses: actions/checkout@v4
      - uses: erlef/setup-beam@v1
        id: beam
        with:
          elixir-version: ${{ env.ELIXIR_VERSION }}
          otp-version: ${{ env.OTP_VERSION }}
      - uses: actions/cache@v4
        with:
          path: |
            deps
            _build
          key: ${{ runner.os }}-mix-dev-${{ hashFiles('mix.lock') }}
          restore-keys: ${{ runner.os }}-mix-dev-
      - uses: actions/cache@v4
        with:
          path: priv/plts
          key: plt-${{ runner.os }}-${{ steps.beam.outputs.otp-version }}-${{ steps.beam.outputs.elixir-version }}-${{ hashFiles('mix.lock') }}
      - run: mix deps.get
      - run: mkdir -p priv/plts
      - run: mix dialyzer --plt
      - run: mix dialyzer --format github

@@ -1,0 +1,58 @@
name: Release
on:
  push:
    branches: [main]
permissions:
  contents: write
jobs:
  release:
    name: Release to Hex.pm
    runs-on: ubuntu-latest
    # Only run when a version-tagged commit lands on main
    if: startsWith(github.event.head_commit.message, 'Release v')
    env:
      MIX_ENV: prod
      ELIXIR_VERSION: "1.17"
      OTP_VERSION: "27"
    steps:
      - uses: actions/checkout@v4
      - uses: erlef/setup-beam@v1
        with:
          elixir-version: ${{ env.ELIXIR_VERSION }}
          otp-version: ${{ env.OTP_VERSION }}
      - run: mix deps.get
      - run: mix compile
      - name: Publish to Hex.pm
        run: mix hex.publish --yes
        env:
          HEX_API_KEY: ${{ secrets.HEX_API_KEY }}
      - name: Extract version
        id: version
        run: |
          VERSION=$(mix eval "IO.puts(Mix.Project.config()[:version])" | head -1)
          echo "version=$VERSION" >> "$GITHUB_OUTPUT"
      - name: Create GitHub Release
        run: |
          gh release create "v${{ steps.version.outputs.version }}" \
            --title "v${{ steps.version.outputs.version }}" \
            --generate-notes
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
      - name: Build docs
        env:
          MIX_ENV: dev
        run: |
          mix deps.get
          mix docs
      - name: Publish docs to Hex.pm
        run: mix hex.publish docs --yes
        env:
          HEX_API_KEY: ${{ secrets.HEX_API_KEY }}

@@ -25,3 +25,6 @@
# Temporary files, for example, from tests.
/tmp/
# Dialyzer PLT files
/priv/plts/

@@ -1,0 +1,26 @@
# Changelog
All notable changes to this project will be documented in this file.
The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
## [0.1.0] - 2026-02-10
### Added
- Git object encoding/decoding (blob, tree, commit, tag) with SHA-1 hashing
- Pluggable storage backends: Filesystem, S3, and Memory
- Ref management: branches, tags, HEAD, compare-and-swap updates
- Packfile support: read/write `.pack` and `.idx` v2 files
- Delta resolution (OFS_DELTA) in pack reader
- Three-way recursive tree merge with conflict detection
- Myers diff algorithm with unified diff output and context hunks
- Commit log traversal and merge base (LCA) finding
- Git wire protocol: pkt-line framing, upload-pack, receive-pack
- ETS-based LRU object cache with configurable size limits
- Atomic file writes and lock-file CAS for filesystem storage
- Path traversal prevention in filesystem storage
- Input validation for refs, SHAs, tree entry names, pack counts
- Apache 2.0 license with headers on all source files
- `mix license_check` task for CI enforcement

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore do
  @moduledoc """
  Pure Elixir Git library with pluggable object storage (S3, filesystem, memory).

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Cache.ETS do
  @moduledoc """
  ETS-based LRU cache for git objects and pack indexes.
@@ -5,11 +19,11 @@
  Objects are immutable by SHA, making them ideal for caching.
  Cache keys are `{repo_id, sha}` tuples.
  Config:
      %{table: :my_cache_table, max_entries: 10_000}
  Uses a separate ordered_set ETS table as an LRU index to avoid
  O(n log n) full-table scans during eviction.
  The caller is responsible for creating the ETS table before use:
      :ets.new(:my_cache, [:set, :public, :named_table])
  Config:
      %{table: :my_cache_table, lru_table: :my_lru_table, max_entries: 10_000}
  """
  @doc """
@@ -27,18 +41,40 @@
        write_concurrency: true
      ])
    lru_table =
    %{table: table, max_entries: max_entries}
      :ets.new(:"#{table_name}_lru", [
        :ordered_set,
        :public,
        write_concurrency: true
      ])
    %{table: table, lru_table: lru_table, max_entries: max_entries}
  end
  @doc """
  Destroy the cache tables, freeing memory.
  """
  @spec destroy(map()) :: :ok
  def destroy(%{table: table, lru_table: lru_table}) do
    :ets.delete(table)
    :ets.delete(lru_table)
    :ok
  end
  @doc """
  Get an object from the cache.
  """
  @spec get(map(), String.t(), String.t()) :: {:ok, term()} | :miss
  def get(%{table: table}, repo_id, key) do
    case :ets.lookup(table, {repo_id, key}) do
      [{_, value, _ts}] ->
        # Update access time for LRU
        :ets.update_element(table, {repo_id, key}, {3, System.monotonic_time()})
  def get(%{table: table, lru_table: lru_table}, repo_id, key) do
    cache_key = {repo_id, key}
    case :ets.lookup(table, cache_key) do
      [{_, value, old_ts}] ->
        new_ts = System.monotonic_time()
        # Update access time in both tables (best-effort, races are acceptable for LRU)
        :ets.update_element(table, cache_key, {3, new_ts})
        :ets.delete(lru_table, {old_ts, cache_key})
        :ets.insert(lru_table, {{new_ts, cache_key}})
        {:ok, value}
      [] ->
@@ -50,14 +86,16 @@
  Put an object into the cache.
  """
  @spec put(map(), String.t(), String.t(), term()) :: :ok
  def put(%{table: table, max_entries: max_entries}, repo_id, key, value) do
    # Check size and evict if needed
  def put(%{table: table, lru_table: lru_table, max_entries: max_entries}, repo_id, key, value) do
    size = :ets.info(table, :size)
    if size >= max_entries do
      evict_oldest(table, div(max_entries, 10))
      evict_oldest(table, lru_table, div(max_entries, 10))
    end
    ts = System.monotonic_time()
    :ets.insert(table, {{repo_id, key}, value, System.monotonic_time()})
    cache_key = {repo_id, key}
    :ets.insert(table, {cache_key, value, ts})
    :ets.insert(lru_table, {{ts, cache_key}})
    :ok
  end
@@ -75,7 +113,10 @@
  Clear all entries for a specific repo.
  """
  @spec clear_repo(map(), String.t()) :: :ok
  def clear_repo(%{table: table}, repo_id) do
  def clear_repo(%{table: table, lru_table: lru_table}, repo_id) do
    :ets.match_delete(table, {{repo_id, :_}, :_, :_})
    # Clearing LRU entries for a specific repo requires a scan,
    # but it's better to just rebuild on next eviction
    :ets.delete_all_objects(lru_table)
    :ok
  end
@@ -84,21 +125,24 @@
  Clear the entire cache.
  """
  @spec clear(map()) :: :ok
  def clear(%{table: table}) do
  def clear(%{table: table, lru_table: lru_table}) do
    :ets.delete_all_objects(table)
    :ets.delete_all_objects(lru_table)
    :ok
  end
  # Evict the N oldest entries by access time
  defp evict_oldest(table, count) do
    # Get all entries sorted by access time
    entries =
      :ets.tab2list(table)
      |> Enum.sort_by(fn {_key, _value, ts} -> ts end)
      |> Enum.take(count)
  # Evict the N oldest entries using the ordered LRU index — O(N) not O(total)
  defp evict_oldest(table, lru_table, count) do
    do_evict(table, lru_table, count, :ets.first(lru_table))
  end
    for {key, _value, _ts} <- entries do
      :ets.delete(table, key)
    end
  defp do_evict(_table, _lru_table, 0, _key), do: :ok
  defp do_evict(_table, _lru_table, _remaining, :"$end_of_table"), do: :ok
  defp do_evict(table, lru_table, remaining, {_ts, cache_key} = lru_key) do
    next = :ets.next(lru_table, lru_key)
    :ets.delete(table, cache_key)
    :ets.delete(lru_table, lru_key)
    do_evict(table, lru_table, remaining - 1, next)
  end
end

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Diff do
  @moduledoc """
  Tree-level diff and line-level diff with hunk formatting.
@@ -236,7 +250,16 @@
  end
  defp group_changes(indexed, context) do
    # Find change regions (del/add) and expand with context
    indexed_vec = :array.from_list(indexed)
    total = :array.size(indexed_vec)
    # Build index map for O(1) position lookups instead of O(n) find_index
    index_map =
      indexed
      |> Enum.with_index()
      |> Map.new(fn {item, idx} -> {item, idx} end)
    # Find change regions using prepend + reverse to avoid O(n²) append
    {groups, current_group} =
      Enum.reduce(indexed, {[], []}, fn item, {groups, current} ->
        case item do
@@ -244,42 +267,43 @@
            if current == [] do
              {groups, []}
            else
              {groups, current ++ [item]}
              {groups, [item | current]}
            end
          _ ->
            {groups, current ++ [item]}
            {groups, [item | current]}
        end
      end)
    all_groups =
      if current_group != [] do
        [Enum.reverse(current_group) | groups]
    all_groups = if current_group != [], do: groups ++ [current_group], else: groups
      else
        groups
      end
      |> Enum.reverse()
    # Add context lines around each group using pre-computed indices
    all_groups
    # Add context lines around each group
    |> Enum.map(fn group -> add_context(group, indexed_vec, total, index_map, context) end)
    Enum.map(all_groups, fn group ->
      add_context(group, indexed, context)
    end)
    |> Enum.reject(&Enum.empty?/1)
  end
  defp add_context(group, all_indexed, context) do
    return_if_empty = fn -> [] end
  defp add_context([], _indexed_vec, _total, _index_map, _context), do: []
  defp add_context(group, indexed_vec, total, index_map, context) do
    first = List.first(group)
    last = List.last(group)
    case {List.first(group), List.last(group)} do
      {nil, _} ->
        return_if_empty.()
      {first, last} ->
        # Find indices in all_indexed
        first_idx = Enum.find_index(all_indexed, &(&1 == first))
        last_idx = Enum.find_index(all_indexed, &(&1 == last))
    first_idx = Map.get(index_map, first)
    last_idx = Map.get(index_map, last)
        if first_idx == nil or last_idx == nil do
          group
        else
          start_idx = max(0, first_idx - context)
    if first_idx == nil or last_idx == nil do
      group
    else
      start_idx = max(0, first_idx - context)
      end_idx = min(total - 1, last_idx + context)
          end_idx = min(length(all_indexed) - 1, last_idx + context)
          Enum.slice(all_indexed, start_idx..end_idx)
        end
      for i <- start_idx..end_idx, do: :array.get(i, indexed_vec)
    end
  end

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Diff.Myers do
  @moduledoc """
  Myers diff algorithm for computing the shortest edit script between two sequences.

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Merge do
  @moduledoc """
  Three-way tree merge.
@@ -9,6 +23,8 @@
  alias ExGitObjectstore.{Object, ObjectResolver, Repo, Walk}
  alias ExGitObjectstore.Object.{Commit, Tree}
  @max_tree_depth 64
  @type conflict :: %{
          path: String.t(),
          base: String.t() | nil,
@@ -58,6 +74,6 @@
    with {:ok, base_tree} <- read_tree(repo, base_tree_sha),
         {:ok, ours_tree} <- read_tree(repo, ours_tree_sha),
         {:ok, theirs_tree} <- read_tree(repo, theirs_tree_sha) do
      merge_tree_entries(repo, base_tree, ours_tree, theirs_tree, "")
      merge_tree_entries(repo, base_tree, ours_tree, theirs_tree, "", 0)
    end
  end
@@ -73,7 +89,12 @@
  end
  # Merge tree entries from all three sides
  defp merge_tree_entries(_repo, _base_tree, _ours_tree, _theirs_tree, _path_prefix, depth)
       when depth > @max_tree_depth do
    {:error, :max_tree_depth_exceeded}
  end
  defp merge_tree_entries(repo, base_tree, ours_tree, theirs_tree, path_prefix) do
  defp merge_tree_entries(repo, base_tree, ours_tree, theirs_tree, path_prefix, depth) do
    base_map = entries_to_map(base_tree.entries)
    ours_map = entries_to_map(ours_tree.entries)
    theirs_map = entries_to_map(theirs_tree.entries)
@@ -93,6 +114,6 @@
        theirs_entry = Map.get(theirs_map, name)
        full_path = join_path(path_prefix, name)
        case merge_entry(repo, base_entry, ours_entry, theirs_entry, full_path) do
        case merge_entry(repo, base_entry, ours_entry, theirs_entry, full_path, depth) do
          {:keep, entry} ->
            {[entry | entries_acc], conflicts_acc}
@@ -120,7 +141,7 @@
  end
  # Three-way merge logic for a single entry
  defp merge_entry(repo, base, ours, theirs, path) do
  defp merge_entry(repo, base, ours, theirs, path, depth) do
    cond do
      # All three identical — no change
      same_entry?(base, ours) and same_entry?(base, theirs) ->
@@ -140,7 +161,7 @@
      # Both changed differently — check if subtrees can be recursively merged
      both_are_trees?(ours, theirs) and (base == nil or is_tree_entry?(base)) ->
        merge_subtrees(repo, base, ours, theirs, path)
        merge_subtrees(repo, base, ours, theirs, path, depth)
      # Conflict: both modified differently (blobs), or delete vs modify
      true ->
@@ -154,16 +175,12 @@
    end
  end
  defp merge_subtrees(repo, base, ours, theirs, path) do
  defp merge_subtrees(repo, base, ours, theirs, path, depth) do
    # For recursive subtree merge, we need actual tree objects
    base_sha = if base, do: base.sha, else: empty_tree_sha(repo)
    ours_sha = ours.sha
    with {:ok, base_sha} <- empty_tree_or_sha(repo, base),
         {:ok, base_tree} <- read_tree(repo, base_sha),
         {:ok, ours_tree} <- read_tree(repo, ours.sha),
    theirs_sha = theirs.sha
    # Use merge_tree_entries directly to keep path prefix context
    with {:ok, base_tree} <- read_tree(repo, base_sha),
         {:ok, ours_tree} <- read_tree(repo, ours_sha),
         {:ok, theirs_tree} <- read_tree(repo, theirs_sha) do
      case merge_tree_entries(repo, base_tree, ours_tree, theirs_tree, path) do
         {:ok, theirs_tree} <- read_tree(repo, theirs.sha) do
      case merge_tree_entries(repo, base_tree, ours_tree, theirs_tree, path, depth + 1) do
        {:ok, merged_sha} ->
          {:keep, %{mode: ours.mode, name: ours.name, sha: merged_sha}}
@@ -177,15 +194,12 @@
    end
  end
  # Create an empty tree and return its SHA for base-less subtree merges
  defp empty_tree_sha(repo) do
  # Return the entry's SHA or write an empty tree for base-less subtree merges
  defp empty_tree_or_sha(repo, nil) do
    Object.write(repo, Tree.new([]))
  end
    tree = Tree.new([])
    case Object.write(repo, tree) do
      {:ok, sha} -> sha
  defp empty_tree_or_sha(_repo, entry), do: {:ok, entry.sha}
      {:error, _} -> raise "Failed to write empty tree"
    end
  end
  defp entries_to_map(entries) do
    Map.new(entries, fn entry -> {entry.name, entry} end)

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Object do
  @moduledoc """
  Git object encoding/decoding.
@@ -33,13 +47,25 @@
  @doc """
  Encode a git object to its stored format (zlib compressed).
  Raises on compression failure (extremely rare).
  """
  @spec encode(t()) :: binary()
  def encode(object) do
    case zlib_compress(encode_raw(object)) do
      {:ok, compressed} -> compressed
      {:error, reason} -> raise "zlib compression failed: #{inspect(reason)}"
    end
    object |> encode_raw() |> zlib_compress()
  end
  @doc """
  Safe version of encode/1 — returns `{:ok, compressed}` or `{:error, reason}`.
  """
  @spec safe_encode(t()) :: {:ok, binary()} | {:error, term()}
  def safe_encode(object) do
    zlib_compress(encode_raw(object))
  end
  @doc """
  Decode a stored git object (zlib compressed) into a struct.
  """
  @spec decode(binary()) :: {:ok, t()} | {:error, term()}
@@ -81,10 +107,15 @@
  @spec write(Repo.t(), t()) :: {:ok, String.t()} | {:error, term()}
  def write(%Repo{} = repo, object) do
    sha = hash(object)
    compressed = encode(object)
    case safe_encode(object) do
      {:ok, compressed} ->
        case Repo.storage_call(repo, :put_object, [sha, compressed]) do
          :ok -> {:ok, sha}
          {:error, _} = err -> err
        end
    case Repo.storage_call(repo, :put_object, [sha, compressed]) do
      :ok -> {:ok, sha}
      {:error, _} = err ->
        err
      {:error, _} = err -> err
    end
  end
@@ -141,11 +172,17 @@
  defp zlib_compress(data) do
    z = :zlib.open()
    :zlib.deflateInit(z)
    compressed = :zlib.deflate(z, data, :finish)
    :zlib.deflateEnd(z)
    :zlib.close(z)
    IO.iodata_to_binary(compressed)
    try do
      :zlib.deflateInit(z)
      compressed = :zlib.deflate(z, data, :finish)
      :zlib.deflateEnd(z)
      {:ok, IO.iodata_to_binary(compressed)}
    rescue
      e -> {:error, {:compress_failed, Exception.message(e)}}
    after
      :zlib.close(z)
    end
  end
  defp safe_decompress(data) do

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Object.Blob do
  @moduledoc """
  Git blob object — stores file content.

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Object.Commit do
  @moduledoc """
  Git commit object.

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Object.Tag do
  @moduledoc """
  Git annotated tag object.

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Object.Tree do
  @moduledoc """
  Git tree object — represents a directory listing.
@@ -21,6 +35,22 @@
  end
  @doc """
  Validate a tree entry name according to git rules.
  Returns `:ok` or `{:error, reason}`.
  """
  @spec validate_entry_name(String.t()) :: :ok | {:error, term()}
  def validate_entry_name(name) do
    cond do
      name == "" -> {:error, {:invalid_entry_name, name, :empty}}
      name == "." -> {:error, {:invalid_entry_name, name, :dot}}
      name == ".." -> {:error, {:invalid_entry_name, name, :dotdot}}
      String.contains?(name, "/") -> {:error, {:invalid_entry_name, name, :slash}}
      String.contains?(name, <<0>>) -> {:error, {:invalid_entry_name, name, :null_byte}}
      true -> :ok
    end
  end
  @doc """
  Encode tree entries to the binary content format.
  Format per entry: `<mode> <name>\0<20-byte-sha>`
  """
@@ -28,7 +58,7 @@
  def encode_content(%__MODULE__{entries: entries}) do
    entries
    |> Enum.map(fn entry ->
      sha_bin = Base.decode16!(String.upcase(entry.sha))
      {:ok, sha_bin} = Base.decode16(String.upcase(entry.sha))
      "#{entry.mode} #{entry.name}\0" <> sha_bin
    end)
    |> IO.iodata_to_binary()

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.ObjectResolver do
  @moduledoc """
  Resolves git objects by checking loose objects first, then searching packs.

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Pack.Delta do
  @moduledoc """
  Git packfile delta decompression.
@@ -23,7 +37,8 @@
  """
  @spec apply(binary(), binary()) :: {:ok, binary()} | {:error, term()}
  def apply(base, delta) do
    with {:ok, base_size, rest} <- read_varint(delta),
    with {:ok, _base_size, rest} <- read_varint(delta),
         :ok <- validate_base_size(base, base_size),
         {:ok, target_size, instructions} <- read_varint(rest),
         {:ok, result} <- apply_instructions(instructions, base, []) do
      result_bin = IO.iodata_to_binary(result)
@@ -50,5 +65,13 @@
  end
  defp read_varint(<<>>, _value, _shift), do: {:error, :truncated_varint}
  defp validate_base_size(base, expected_size) do
    if byte_size(base) == expected_size do
      :ok
    else
      {:error, {:base_size_mismatch, expected: expected_size, got: byte_size(base)}}
    end
  end
  defp apply_instructions(<<>>, _base, acc), do: {:ok, Enum.reverse(acc)}

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Pack.Index do
  @moduledoc """
  Parser for git pack index files (.idx), version 2 format.
@@ -29,16 +43,19 @@
  @doc """
  Parse a .idx v2 binary into an Index struct.
  """
  @max_pack_objects 10_000_000
  @spec parse(binary()) :: {:ok, t()} | {:error, term()}
  def parse(<<@idx_magic, @idx_version, rest::binary>>) do
    with {:ok, fanout, rest} <- parse_fanout(rest),
         count = elem(fanout, 255),
         :ok <- validate_fanout(fanout),
         :ok <- validate_count(count),
         {:ok, shas, rest} <- parse_shas(rest, count),
         {:ok, _crcs, rest} <- parse_crcs(rest, count),
         {:ok, offsets_4, rest} <- parse_offsets_4(rest, count),
         {:ok, large_offsets} <- parse_large_offsets(rest, offsets_4) do
      offset_map = build_offset_map(shas, offsets_4, large_offsets)
         {:ok, large_offsets} <- parse_large_offsets(rest, offsets_4),
         {:ok, offset_map} <- build_offset_map(shas, offsets_4, large_offsets) do
      {:ok,
       %__MODULE__{
         fanout: fanout,
@@ -165,17 +182,45 @@
      end
    end
  end
  defp validate_fanout(fanout) do
    # Fanout table must be monotonically non-decreasing
    values = Tuple.to_list(fanout)
    if values == Enum.sort(values) do
      :ok
    else
      {:error, :fanout_not_monotonic}
    end
  end
  defp validate_count(count) when count > @max_pack_objects do
    {:error, {:pack_too_large, count}}
  end
  defp validate_count(_count), do: :ok
  defp build_offset_map(shas, offsets_4, large_offsets) do
    result =
      shas
      |> Enum.zip(offsets_4)
      |> Map.new(fn {sha, offset_4} ->
        if Bitwise.band(offset_4, 0x80000000) != 0 do
          large_idx = Bitwise.band(offset_4, 0x7FFFFFFF)
          case Map.get(large_offsets, large_idx) do
            nil -> {sha, {:error, {:missing_large_offset, large_idx}}}
            offset -> {sha, offset}
          end
        else
          {sha, offset_4}
        end
    shas
    |> Enum.zip(offsets_4)
    |> Map.new(fn {sha, offset_4} ->
      if Bitwise.band(offset_4, 0x80000000) != 0 do
        large_idx = Bitwise.band(offset_4, 0x7FFFFFFF)
        {sha, Map.fetch!(large_offsets, large_idx)}
      else
        {sha, offset_4}
      end
    end)
      end)
    # Check if any entries had errors
    case Enum.find(result, fn {_sha, val} -> match?({:error, _}, val) end) do
      nil -> {:ok, result}
      {_sha, err} -> err
    end
  end
end

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Pack.Reader do
  @moduledoc """
  Packfile reader — parses objects from .pack files.
@@ -17,6 +31,7 @@
  alias ExGitObjectstore.Pack.Delta
  @pack_signature "PACK"
  @max_pack_objects 10_000_000
  # Object types (3-bit)
  @obj_commit 1
@@ -39,8 +54,12 @@
  @spec parse(binary()) :: {:ok, [pack_object()]} | {:error, term()}
  def parse(<<@pack_signature, version::unsigned-big-32, count::unsigned-big-32, rest::binary>>)
      when version == 2 do
    case parse_entries(rest, count, [], %{}) do
      {:ok, entries, _cache} -> {:ok, entries}
      {:error, _} = err -> err
    if count > @max_pack_objects do
      {:error, {:pack_too_large, count}}
    else
      case parse_entries(rest, count, [], %{}) do
        {:ok, entries, _cache} -> {:ok, entries}
        {:error, _} = err -> err
      end
    end
  end
@@ -271,5 +290,8 @@
  defp parse_ofs_continuation(<<>>, _offset, _consumed), do: {:error, :truncated_ofs_offset}
  # Decompress data and find the exact compressed length.
  # Uses inflate for decompression, then binary search to find the minimal
  # prefix that produces the same output. This is O(log n) decompressions.
  defp decompress_data(compressed) do
    z = :zlib.open()
@@ -280,7 +302,6 @@
      decompressed_bin = IO.iodata_to_binary(decompressed)
      :zlib.inflateEnd(z)
      # Find the exact compressed length by re-compressing and probing
      compressed_len = find_compressed_length(compressed, byte_size(decompressed_bin))
      {:ok, decompressed_bin, compressed_len}
    rescue
@@ -290,8 +311,6 @@
    end
  end
  # Find compressed length by binary probing: try increasingly smaller
  # prefixes until decompression still produces the same output
  defp find_compressed_length(compressed, expected_size) do
    total = byte_size(compressed)
    probe_compressed_length(compressed, expected_size, 1, total)
@@ -302,11 +321,9 @@
    case try_decompress_prefix(compressed, mid) do
      {:ok, size} when size == expected_size ->
        # This prefix is enough — try shorter
        probe_compressed_length(compressed, expected_size, low, mid)
      _ ->
        # This prefix is not enough — try longer
        probe_compressed_length(compressed, expected_size, mid + 1, high)
    end
  end
@@ -335,9 +352,12 @@
  defp type_num_to_atom(@obj_blob), do: :blob
  defp type_num_to_atom(@obj_tag), do: :tag
  # TODO: Implement REF_DELTA resolution by building an in-memory index from
  # the pack data. Currently REF_DELTA objects can only be resolved when the
  # caller provides offsets via the cache (e.g., from a .idx file lookup).
  # Without this, thin packs from git-fetch that use REF_DELTA will fail.
  # See: https://git-scm.com/docs/pack-format#_deltified_representation
  defp find_sha_offset(_pack_data, _sha, _cache) do
    {:error, :ref_delta_not_supported}
    # This would need an index lookup. For now, return an error.
    # The caller should have provided the offset via cache.
    {:error, :ref_delta_needs_index}
  end
end

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Pack.Writer do
  @moduledoc """
  Generate git packfiles and their corresponding .idx files from a set of objects.
@@ -130,7 +144,7 @@
    # SHA table
    sha_data =
      sorted
      |> Enum.map(fn {sha, _offset, _crc} -> Base.decode16!(sha, case: :lower) end)
      |> Enum.map(fn {sha, _offset, _crc} -> elem(Base.decode16(sha, case: :mixed), 1) end)
      |> IO.iodata_to_binary()
    # CRC table
@@ -169,6 +183,6 @@
    # 256 entries, each is cumulative count of objects with first SHA byte <= N
    sha_first_bytes =
      Enum.map(sorted_entries, fn {sha, _offset, _crc} ->
        <<first_byte, _rest::binary>> = Base.decode16!(sha, case: :lower)
        <<first_byte, _rest::binary>> = elem(Base.decode16(sha, case: :mixed), 1)
        first_byte
      end)
@@ -209,10 +223,16 @@
  defp zlib_compress(data) do
    z = :zlib.open()
    try do
      :zlib.deflateInit(z)
      compressed = :zlib.deflate(z, data, :finish)
      :zlib.deflateEnd(z)
      IO.iodata_to_binary(compressed)
    rescue
      e -> {:error, {:compress_failed, Exception.message(e)}}
    :zlib.deflateInit(z)
    compressed = :zlib.deflate(z, data, :finish)
    :zlib.deflateEnd(z)
    :zlib.close(z)
    IO.iodata_to_binary(compressed)
    after
      :zlib.close(z)
    end
  end
end

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Protocol.PktLine do
  @moduledoc """
  Git pkt-line format encoding and decoding.

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Protocol.ReceivePack do
  @moduledoc """
  State machine for the git receive-pack protocol (server side of `git push`).
@@ -18,8 +32,12 @@
  alias ExGitObjectstore.Protocol.PktLine
  @zero_sha String.duplicate("0", 40)
  @capabilities "report-status delete-refs ofs-delta side-band-64k"
  # Capabilities we actually implement. Others are scaffolded but not yet functional:
  # TODO: ofs-delta — Writer doesn't generate OFS_DELTA yet
  # TODO: side-band-64k — not yet used in report responses
  @capabilities "report-status delete-refs"
  @type command :: %{
          ref: String.t(),
          old_sha: String.t(),
@@ -314,10 +332,16 @@
  defp zlib_compress(data) do
    z = :zlib.open()
    :zlib.deflateInit(z)
    try do
    compressed = :zlib.deflate(z, data, :finish)
    :zlib.deflateEnd(z)
    :zlib.close(z)
    IO.iodata_to_binary(compressed)
      :zlib.deflateInit(z)
      compressed = :zlib.deflate(z, data, :finish)
      :zlib.deflateEnd(z)
      IO.iodata_to_binary(compressed)
    rescue
      e -> {:error, {:compress_failed, Exception.message(e)}}
    after
      :zlib.close(z)
    end
  end
end

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Protocol.UploadPack do
  @moduledoc """
  State machine for the git upload-pack protocol (server side of `git fetch/clone`).
@@ -16,8 +30,12 @@
  alias ExGitObjectstore.Protocol.PktLine
  @zero_sha String.duplicate("0", 40)
  @capabilities "multi_ack_detailed side-band-64k ofs-delta"
  # Capabilities we actually implement. Others are scaffolded but not yet functional:
  # TODO: multi_ack_detailed — requires returning ACK during negotiation, currently NAK-only
  # TODO: ofs-delta — reader supports OFS_DELTA, but Writer doesn't generate them yet
  @capabilities "side-band-64k"
  @type state :: %__MODULE__{
          repo: Repo.t(),
          phase: :advertise | :negotiation | :pack | :done,
@@ -83,14 +101,16 @@
  defp build_advertisement(repo) do
    refs = list_all_refs(repo)
    symref = head_symref(repo)
    caps = build_capabilities(symref)
    case refs do
      [] ->
        line = "#{@zero_sha} capabilities^{}\0 #{caps}"
        line = "#{@zero_sha} capabilities^{}\0 #{@capabilities}"
        PktLine.encode(line) <> PktLine.flush()
      [{first_ref, first_sha} | rest] ->
        first_line = "#{first_sha} #{first_ref}\0 #{@capabilities}"
        first_line = "#{first_sha} #{first_ref}\0 #{caps}"
        lines =
          [PktLine.encode(first_line)] ++
@@ -102,6 +122,16 @@
        IO.iodata_to_binary(lines)
    end
  end
  defp head_symref(repo) do
    case Ref.get_head(repo) do
      {:ok, "ref: " <> ref_path} -> ref_path
      _ -> nil
    end
  end
  defp build_capabilities(nil), do: @capabilities
  defp build_capabilities(ref), do: "#{@capabilities} symref=HEAD:#{ref}"
  defp list_all_refs(repo) do
    heads =

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Ref do
  @moduledoc """
  Git reference management — branches, tags, and HEAD.
@@ -18,7 +32,11 @@
  """
  @spec put(Repo.t(), String.t(), String.t(), String.t() | nil) :: :ok | {:error, term()}
  def put(%Repo{} = repo, ref_path, new_sha, old_sha) do
    Repo.storage_call(repo, :put_ref, [ref_path, new_sha, old_sha])
    with :ok <- validate_sha(new_sha),
         :ok <- validate_ref_name(ref_path),
         :ok <- if(old_sha, do: validate_sha(old_sha), else: :ok) do
      Repo.storage_call(repo, :put_ref, [ref_path, new_sha, old_sha])
    end
  end
  @doc """
@@ -100,4 +118,48 @@
  end
  defp sha?(_), do: false
  @doc """
  Validate that a string is a valid 40-character lowercase hex SHA.
  """
  @spec validate_sha(String.t()) :: :ok | {:error, term()}
  def validate_sha(sha) do
    if sha?(sha) do
      :ok
    else
      {:error, {:invalid_sha, sha}}
    end
  end
  @doc """
  Validate a ref name according to git rules.
  """
  @spec validate_ref_name(String.t()) :: :ok | {:error, term()}
  def validate_ref_name(ref_path) do
    cond do
      ref_path == "" ->
        {:error, {:invalid_ref_name, ref_path, :empty}}
      String.contains?(ref_path, "..") ->
        {:error, {:invalid_ref_name, ref_path, :dotdot}}
      String.ends_with?(ref_path, ".lock") ->
        {:error, {:invalid_ref_name, ref_path, :lock_suffix}}
      String.contains?(ref_path, "//") ->
        {:error, {:invalid_ref_name, ref_path, :double_slash}}
      String.contains?(ref_path, <<0>>) ->
        {:error, {:invalid_ref_name, ref_path, :null_byte}}
      String.ends_with?(ref_path, "/") ->
        {:error, {:invalid_ref_name, ref_path, :trailing_slash}}
      String.starts_with?(ref_path, "/") ->
        {:error, {:invalid_ref_name, ref_path, :leading_slash}}
      true ->
        :ok
    end
  end
end

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Repo do
  @moduledoc """
  Repository handle. Encapsulates the repo identity and storage backend config.

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Storage do
  @moduledoc """
  Behaviour for pluggable git object storage backends.

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Storage.Filesystem do
  @moduledoc """
  Local filesystem storage backend.
@@ -17,6 +31,8 @@
  @behaviour ExGitObjectstore.Storage
  @max_recursive_depth 20
  # -- Object operations --
  @impl true
@@ -33,9 +49,7 @@
  @impl true
  def put_object(config, prefix, sha, data) do
    path = object_path(config, prefix, sha)
    File.mkdir_p!(Path.dirname(path))
    atomic_write(path, data)
    File.write!(path, data)
    :ok
  end
  @impl true
@@ -96,10 +110,11 @@
  def put_pack(config, prefix, pack_sha, pack_data, idx_data) do
    pack_p = pack_path(config, prefix, pack_sha, "pack")
    idx_p = pack_path(config, prefix, pack_sha, "idx")
    with :ok <- atomic_write(pack_p, pack_data),
         :ok <- atomic_write(idx_p, idx_data) do
    File.mkdir_p!(Path.dirname(pack_p))
    File.write!(pack_p, pack_data)
      :ok
    end
    File.write!(idx_p, idx_data)
    :ok
  end
  @impl true
@@ -130,28 +145,50 @@
  @impl true
  def put_ref(config, prefix, ref_path, new_sha, old_sha) do
    path = Path.join([config.root, prefix, ref_path])
    lock_path = path <> ".lock"
    File.mkdir_p!(Path.dirname(path))
    if old_sha do
      # CAS: check current value
      case File.read(path) do
        {:ok, data} ->
    # Use lock file for atomicity
    case File.open(lock_path, [:write, :exclusive]) do
      {:ok, lock_fd} ->
        try do
          IO.binwrite(lock_fd, new_sha <> "\n")
          File.close(lock_fd)
          if old_sha do
            # CAS: verify current value under lock
            case File.read(path) do
              {:ok, data} ->
                if String.trim(data) == old_sha do
                  File.rename!(lock_path, path)
                  :ok
                else
                  File.rm(lock_path)
                  {:error, :cas_failed}
                end
              {:error, :enoent} ->
                File.rm(lock_path)
                {:error, :cas_failed}
              {:error, reason} ->
                File.rm(lock_path)
                {:error, reason}
            end
          if String.trim(data) == old_sha do
            File.mkdir_p!(Path.dirname(path))
            File.write!(path, new_sha <> "\n")
            :ok
          else
            {:error, :cas_failed}
            File.rename!(lock_path, path)
            :ok
          end
        rescue
          e ->
            File.rm(lock_path)
            {:error, {:lock_failed, Exception.message(e)}}
        end
      {:error, :eexist} ->
        {:error, :enoent} ->
          {:error, :cas_failed}
        {:error, :ref_locked}
        {:error, reason} ->
          {:error, reason}
      end
    else
      {:error, reason} ->
        {:error, reason}
      File.mkdir_p!(Path.dirname(path))
      File.write!(path, new_sha <> "\n")
      :ok
    end
  end
@@ -214,21 +251,53 @@
  @impl true
  def put_head(config, prefix, target) do
    path = Path.join([config.root, prefix, "HEAD"])
    atomic_write(path, target <> "\n")
    File.mkdir_p!(Path.dirname(path))
    File.write!(path, target <> "\n")
    :ok
  end
  # -- Private --
  defp object_path(config, prefix, sha) do
    <<dir::binary-size(2), rest::binary>> = sha
    Path.join([config.root, prefix, "objects", dir, rest])
    safe_path(config.root, Path.join([prefix, "objects", dir, rest]))
  end
  defp pack_path(config, prefix, pack_sha, ext) do
    safe_path(config.root, Path.join([prefix, "objects", "pack", "pack-#{pack_sha}.#{ext}"]))
  end
  # Ensure constructed paths cannot escape the storage root via ".." traversal
  defp safe_path(root, relative) do
    full = Path.join(root, relative) |> Path.expand()
    root_expanded = Path.expand(root)
    if String.starts_with?(full, root_expanded <> "/") or full == root_expanded do
      full
    else
      raise ArgumentError, "path traversal detected: #{relative}"
    Path.join([config.root, prefix, "objects", "pack", "pack-#{pack_sha}.#{ext}"])
    end
  end
  # Atomic write: write to temp file then rename, preventing partial writes
  defp atomic_write(path, data) do
    dir = Path.dirname(path)
    File.mkdir_p!(dir)
    tmp_path = path <> ".tmp.#{:erlang.unique_integer([:positive])}"
    with :ok <- File.write(tmp_path, data) do
      case File.rename(tmp_path, path) do
        :ok ->
          :ok
        {:error, reason} ->
          File.rm(tmp_path)
          {:error, reason}
      end
    else
      {:error, reason} ->
        File.rm(tmp_path)
        {:error, reason}
    end
  end
  defp get_packed_ref(config, prefix, ref_path) do
    packed_refs_path = Path.join([config.root, prefix, "packed-refs"])
@@ -276,8 +345,14 @@
    |> Enum.reject(&is_nil/1)
    |> Map.new()
  end
  defp list_files_recursive(dir), do: list_files_recursive(dir, 0)
  defp list_files_recursive(dir) do
  defp list_files_recursive(_dir, depth) when depth > @max_recursive_depth do
    {:ok, []}
  end
  defp list_files_recursive(dir, depth) do
    case File.ls(dir) do
      {:ok, entries} ->
        files =
@@ -285,7 +360,7 @@
            path = Path.join(dir, entry)
            if File.dir?(path) do
              case list_files_recursive(path) do
              case list_files_recursive(path, depth + 1) do
                {:ok, sub_files} -> sub_files
                _ -> []
              end

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Storage.Memory do
  @moduledoc """
  In-memory storage backend for testing.
@@ -119,16 +133,15 @@
      current = get_in(state, [:refs, key(prefix, ref_path)])
      cond do
        old_sha == nil and current == nil ->
          {:ok, put_in(state, [:refs, key(prefix, ref_path)], new_sha)}
        # No CAS requested: unconditional write
        old_sha == nil ->
          # Creating new ref but it already exists — allow overwrite when no CAS
          {:ok, put_in(state, [:refs, key(prefix, ref_path)], new_sha)}
        # CAS: current matches expected
        current == old_sha ->
          {:ok, put_in(state, [:refs, key(prefix, ref_path)], new_sha)}
        # CAS: mismatch
        true ->
          {{:error, :cas_failed}, state}
      end

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Storage.S3 do
  @moduledoc """
  S3-compatible storage backend (AWS S3, MinIO, etc.).
@@ -240,15 +254,27 @@
  end
  defp s3_list(config, prefix) do
    op = ExAws.S3.list_objects_v2(config.bucket, prefix: prefix)
    s3_list_all(config, prefix, nil, [])
  end
  defp s3_list_all(config, prefix, continuation_token, acc) do
    opts =
      [prefix: prefix] ++
        if(continuation_token, do: [continuation_token: continuation_token], else: [])
    op = ExAws.S3.list_objects_v2(config.bucket, opts)
    case ExAws.request(op, ex_aws_config(config)) do
      {:ok, %{body: %{contents: contents, is_truncated: "true", next_continuation_token: token}}} ->
        keys = Enum.map(contents, & &1.key)
        s3_list_all(config, prefix, token, acc ++ keys)
      {:ok, %{body: %{contents: contents}}} ->
        keys = Enum.map(contents, & &1.key)
        {:ok, keys}
        {:ok, acc ++ keys}
      {:ok, %{body: _}} ->
        {:ok, []}
        {:ok, acc}
      {:error, reason} ->
        {:error, reason}

@@ -1,3 +1,17 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule ExGitObjectstore.Walk do
  @moduledoc """
  Commit graph traversal — implements `git log` style iteration.
@@ -8,6 +22,8 @@
  alias ExGitObjectstore.{ObjectResolver, Repo}
  alias ExGitObjectstore.Object.Commit
  @default_ancestor_limit 100_000
  @type log_opts :: [
          max_count: non_neg_integer(),
          skip: non_neg_integer(),
@@ -57,11 +73,17 @@
  @doc """
  Find the merge base (lowest common ancestor) of two commits.
  ## Options
    * `:ancestor_limit` — max commits to walk when building ancestor sets
      (default: #{@default_ancestor_limit})
  """
  @spec merge_base(Repo.t(), String.t(), String.t(), keyword()) ::
          {:ok, String.t()} | {:error, term()}
  def merge_base(%Repo{} = repo, sha_a, sha_b, opts \\ []) do
  @spec merge_base(Repo.t(), String.t(), String.t()) :: {:ok, String.t()} | {:error, term()}
  def merge_base(%Repo{} = repo, sha_a, sha_b) do
    limit = Keyword.get(opts, :ancestor_limit, @default_ancestor_limit)
    # Build ancestor sets for both commits, find the first common ancestor
    case {ancestor_set(repo, sha_a), ancestor_set(repo, sha_b)} do
    case {ancestor_set(repo, sha_a, limit), ancestor_set(repo, sha_b, limit)} do
      {{:ok, set_a}, {:ok, set_b}} ->
        # Walk from sha_a in order, find first commit that's also in set_b
        common = MapSet.intersection(set_a, set_b)
@@ -116,16 +138,18 @@
    )
  end
  defp parse_timestamp(author_or_committer) when is_binary(author_or_committer) do
  defp parse_timestamp(author_or_committer) do
    # Format: "Name <email> timestamp timezone"
    case Regex.run(~r/(\d+)\s+[+-]\d{4}$/, author_or_committer) do
      [_, timestamp_str] -> String.to_integer(timestamp_str)
      _ -> 0
    end
  end
  defp parse_timestamp(_), do: 0
  defp ancestor_set(repo, sha) do
    case walk(repo, [sha], MapSet.new(), [], 10_000) do
  defp ancestor_set(repo, sha, limit) do
    case walk(repo, [sha], MapSet.new(), [], limit) do
      {:ok, commits} ->
        set = commits |> Enum.map(&elem(&1, 0)) |> MapSet.new()
        {:ok, set}

@@ -1,0 +1,65 @@
# Copyright 2026 Cole Christensen
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule Mix.Tasks.LicenseCheck do
  @moduledoc """
  Checks that all .ex and .exs source files contain the Apache 2.0 license header.
  ## Usage
      mix license_check
  Returns exit code 1 if any files are missing the header.
  """
  @shortdoc "Verify Apache 2.0 license headers on all source files"
  use Mix.Task
  @expected_first_line "# Copyright 2026 Cole Christensen"
  @impl Mix.Task
  def run(_args) do
    files =
      (Path.wildcard("lib/**/*.ex") ++
         Path.wildcard("test/**/*.ex") ++
         Path.wildcard("test/**/*.exs") ++
         ["mix.exs"])
      |> Enum.filter(&File.exists?/1)
    missing =
      Enum.filter(files, fn file ->
        case File.open(file, [:read, :utf8]) do
          {:ok, device} ->
            first_line = IO.read(device, :line) |> String.trim_trailing()
            File.close(device)
            first_line != @expected_first_line
          {:error, _} ->
            true
        end
      end)
    if missing == [] do
      Mix.shell().info("All #{length(files)} files have license headers.")
    else
      Mix.shell().error("Missing license header in #{length(missing)} file(s):")
      Enum.each(missing, fn file ->
        Mix.shell().error("  #{file}")
      end)
      Mix.raise("License check failed. Add the Apache 2.0 header to the files listed above.")
    end
  end
end

@@ -1,1 +1,201 @@
                                 Apache License
                           Version 2.0, January 2004
                        http://www.apache.org/licenses/
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   Copyright 2026 Cole Christensen
   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at
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   Unless required by applicable law or agreed to in writing, software
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   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
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