Make it possible to create new git indices

The API allows for creating brand new index/tree objects, but the
implementation didn't take into account that git update-index expects
the file to be non-existent instead of being zero-sized.

Change-Id: I4b380154626d037da62bf05a90b62d61bc92f8ee
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@qt.io>

2 files changed, 40 insertions, 0 deletions

diff --git a/src/qtmoduleupdater/repo.go b/src/qtmoduleupdater/repo.go
index 2f6e3efd..26cca03e 100644
--- a/src/qtmoduleupdater/repo.go
+++ b/src/qtmoduleupdater/repo.go
@@ -280,6 +280,7 @@ type Index struct {
 	file          *os.File
 	repo          Repository
 	cachedEntries []IndexEntry
+	populated     bool
 }
 
 // NewIndex creates a new git index based on a temporary file. Unless you'd like to
@@ -293,6 +294,7 @@ func (repo Repository) NewIndex() (result *Index, err error) {
 	if err != nil {
 		return nil, err
 	}
+	result.populated = false
 	return result, nil
 }
 
@@ -395,15 +397,20 @@ func (idx *Index) ReadTree(tree OID) error {
 	if err != nil {
 		return err
 	}
+	idx.populated = true
 	return idx.updateCachedEntries()
 }
 
 // Add adds a new entry to the index or updates an existing one if already present.
 func (idx *Index) Add(entry *IndexEntry) error {
+	if !idx.populated {
+		os.Remove(idx.file.Name())
+	}
 	_, err := idx.gitCommandWithIndex("update-index", "--add", "--cacheinfo", fmt.Sprintf("%s,%s,%s", entry.Permissions, entry.ID, entry.Path)).Run()
 	if err != nil {
 		return err
 	}
+	idx.populated = true
 	return idx.updateCachedEntries()
 }
 
diff --git a/src/qtmoduleupdater/repo_test.go b/src/qtmoduleupdater/repo_test.go
index 4b478ffc..8a77eec1 100644
--- a/src/qtmoduleupdater/repo_test.go
+++ b/src/qtmoduleupdater/repo_test.go
@@ -30,6 +30,8 @@ package main
 import (
 	"strings"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestRepo(t *testing.T) {
@@ -127,6 +129,37 @@ func TestIndex(t *testing.T) {
 	}
 }
 
+func TestNewIndex(t *testing.T) {
+	repo, err := OpenRepository("qt/qtbase")
+	assert.Nilf(t, err, "Unexpected error opening qtbase repo: %s", err)
+
+	index, err := repo.NewIndex()
+	if err != nil {
+		t.Fatalf("Could not get index.")
+	}
+	defer index.Free()
+
+	sampleContent := []byte("Hello World")
+
+	indexEntry := &IndexEntry{
+		Permissions: "100644",
+		Path:        "test.txt",
+	}
+
+	err = index.HashObject(indexEntry, sampleContent)
+	assert.Nilf(t, err, "should be able to add data to git database: %s", err)
+
+	assert.Equal(t, OID("5e1c309dae7f45e0f39b1bf3ac3cd9db12e7d689"), indexEntry.ID)
+
+	err = index.Add(indexEntry)
+	assert.Nilf(t, err, "should be able to add entry to new index: %s", err)
+
+	tree, err := index.WriteTree()
+	assert.Nilf(t, err, "should be able to write tree: %s", err)
+
+	assert.Equal(t, OID("4f11af3e4e067fc319abd053205f39bc40652f05"), tree)
+}
+
 func TestLog(t *testing.T) {
 	repo, err := OpenRepository("qt/qtbase")
 	if err != nil {