Urgh I made some wrong amends and I'm too tired to separate the commits out this time

ancestor: Split out of reachability
mergebase: Add merge base routines
internal/commitquery: Add commit query context engine thingy
internal/peel: Shared tag peeling
errors: Shared object query errors
internal/testgit: Add rooted repo helpers; remove raw path access
objectstore/memory: Add in-memory object store
objectid: Add Compare helper

1 files changed, 86 insertions, 0 deletions

diff --git a/internal/testgit/repo_fs.go b/internal/testgit/repo_fs.go
new file mode 100644
index 00000000..56acbfcf
--- /dev/null
+++ b/internal/testgit/repo_fs.go
@@ -0,0 +1,86 @@
+package testgit
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// OpenFile opens one file relative to the repository root.
+func (testRepo *TestRepo) OpenFile(tb testing.TB, name string) *os.File {
+	tb.Helper()
+
+	root := testRepo.OpenRoot(tb)
+
+	file, err := root.Open(name)
+	if err != nil {
+		tb.Fatalf("Open(%q): %v", name, err)
+	}
+
+	return file
+}
+
+// ReadFile reads one file relative to the repository root.
+func (testRepo *TestRepo) ReadFile(tb testing.TB, name string) []byte {
+	tb.Helper()
+
+	root := testRepo.OpenRoot(tb)
+
+	data, err := root.ReadFile(name)
+	if err != nil {
+		tb.Fatalf("ReadFile(%q): %v", name, err)
+	}
+
+	return data
+}
+
+// WriteFile writes one file relative to the repository root.
+func (testRepo *TestRepo) WriteFile(tb testing.TB, name string, data []byte, perm os.FileMode) {
+	tb.Helper()
+
+	root := testRepo.OpenRoot(tb)
+
+	err := root.WriteFile(name, data, perm)
+	if err != nil {
+		tb.Fatalf("WriteFile(%q): %v", name, err)
+	}
+}
+
+// WriteFileAll writes one file relative to the repository root, creating any
+// missing parent directories first.
+func (testRepo *TestRepo) WriteFileAll(
+	tb testing.TB,
+	name string,
+	data []byte,
+	dirPerm os.FileMode,
+	filePerm os.FileMode,
+) {
+	tb.Helper()
+
+	root := testRepo.OpenRoot(tb)
+
+	dir := filepath.Dir(name)
+	if dir != "." {
+		err := root.MkdirAll(dir, dirPerm)
+		if err != nil {
+			tb.Fatalf("MkdirAll(%q): %v", dir, err)
+		}
+	}
+
+	err := root.WriteFile(name, data, filePerm)
+	if err != nil {
+		tb.Fatalf("WriteFile(%q): %v", name, err)
+	}
+}
+
+// Remove removes one path relative to the repository root.
+func (testRepo *TestRepo) Remove(tb testing.TB, name string) {
+	tb.Helper()
+
+	root := testRepo.OpenRoot(tb)
+
+	err := root.Remove(name)
+	if err != nil {
+		tb.Fatalf("Remove(%q): %v", name, err)
+	}
+}