base setup for index testing (#293)

It should be easy enough to learn from git tests to generate whichever
kind of index we need.

Author: Byron

Cargo.lock

@@ -13,3 +13,9 @@ doctest = false
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+git-hash = { version ="^0.8.0", path = "../git-hash" }
+
+quick-error = "2.0.0"
+
+[dev-dependencies]
+git-testtools = { path = "../tests/tools"}

git-index/Cargo.toml

@@ -1 +1,48 @@
-#![forbid(unsafe_code, rust_2018_idioms)]
+#![forbid(unsafe_code)]
+#![deny(rust_2018_idioms)]
+#![allow(missing_docs)]
+
+use std::path::PathBuf;
+
+pub mod file {
+    pub mod init {
+        #![allow(unused)]
+        use crate::File;
+        use std::path::Path;
+
+        impl File {
+            pub fn at(path: impl AsRef<Path>, object_hash: git_hash::Kind) -> std::io::Result<Self> {
+                todo!("read file")
+            }
+        }
+    }
+}
+pub mod init {
+    use crate::State;
+
+    impl State {
+        /// Returns an empty state.
+        /// TODO: figure out if it needs to know some configuration
+        pub fn new() -> Self {
+            State
+        }
+    }
+
+    impl Default for State {
+        fn default() -> Self {
+            State::new()
+        }
+    }
+}
+
+/// An index file whose state was read from a file on disk.
+pub struct File {
+    pub state: State,
+    pub path: PathBuf,
+}
+
+/// An in-memory cache of a fully parsed git index file.
+///
+/// As opposed to a snapshot, it's meant to be altered and eventually be written back to disk or converted into a tree.
+/// We treat index and its state synonymous.
+pub struct State;

git-index/src/lib.rs

@@ -0,0 +1,8 @@
+mod init {
+
+    #[test]
+    #[ignore]
+    fn v2() {
+        let _file = git_index::File::at(crate::index_fixture_path("v2"), git_hash::Kind::Sha1).unwrap();
+    }
+}

git-index/tests/file/mod.rs

@@ -0,0 +1,9 @@
+#!/bin/bash
+set -eu -o pipefail
+
+GIT_INDEX_VERSION=2 git init -q
+git config commit.gpgsign false
+
+touch a
+git add a
+git commit -m "empty"

git-index/tests/fixtures/make_index/v2.sh

@@ -0,0 +1,9 @@
+use std::path::{Path, PathBuf};
+
+mod file;
+
+pub fn index_fixture_path(name: &str) -> PathBuf {
+    let dir = git_testtools::scripted_fixture_repo_read_only(Path::new("make_index").join(name).with_extension("sh"))
+        .expect("script works");
+    dir.join(".git").join("index")
+}

git-index/tests/index.rs

@@ -19,7 +19,9 @@ pub fn hex_to_id(hex: &str) -> git_hash::ObjectId {
 pub fn fixture_path(path: impl AsRef<Path>) -> PathBuf {
     PathBuf::from("tests").join("fixtures").join(path.as_ref())
 }
-pub fn scripted_fixture_repo_read_only(script_name: &str) -> std::result::Result<PathBuf, Box<dyn std::error::Error>> {
+pub fn scripted_fixture_repo_read_only(
+    script_name: impl AsRef<Path>,
+) -> std::result::Result<PathBuf, Box<dyn std::error::Error>> {
     scripted_fixture_repo_read_only_with_args(script_name, None)
 }
 
@@ -59,7 +61,7 @@ pub fn copy_recursively_into_existing_dir(src_dir: impl AsRef<Path>, dst_dir: im
 
 /// Returns the directory at which the data is present
 pub fn scripted_fixture_repo_read_only_with_args(
-    script_name: &str,
+    script_name: impl AsRef<Path>,
     args: impl IntoIterator<Item = &'static str>,
 ) -> std::result::Result<PathBuf, Box<dyn std::error::Error>> {
     let script_path = fixture_path(script_name);