plumbing: filemode, Remove check for setting size of .git/index file (#1159)

* plumbing: filemode, Remove check for setting size of .git/index file on staging. Fixes #1003

Co-authored-by: Paulo Gomes <paulo.gomes.uk@gmail.com>

2 files changed, 94 insertions, 3 deletions

diff --git a/worktree_status.go b/worktree_status.go
index 6a0049c..f6b8282 100644
--- a/worktree_status.go
+++ b/worktree_status.go
@@ -559,9 +559,11 @@ func (w *Worktree) doUpdateFileToIndex(e *index.Entry, filename string, h plumbi
 		return err
 	}
 
-	if e.Mode.IsRegular() {
-		e.Size = uint32(info.Size())
-	}
+	// The entry size must always reflect the current state, otherwise
+	// it will cause go-git's Worktree.Status() to divert from "git status".
+	// The size of a symlink is the length of the path to the target.
+	// The size of Regular and Executable files is the size of the files.
+	e.Size = uint32(info.Size())
 
 	fillSystemInfo(e, info.Sys())
 	return nil
diff --git a/worktree_status_test.go b/worktree_status_test.go
new file mode 100644
index 0000000..629ebd5
--- /dev/null
+++ b/worktree_status_test.go
@@ -0,0 +1,89 @@
+package git
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/go-git/go-billy/v5/osfs"
+	"github.com/go-git/go-git/v5/plumbing/cache"
+	"github.com/go-git/go-git/v5/storage/filesystem"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// For additional context: #1159.
+func TestIndexEntrySizeUpdatedForNonRegularFiles(t *testing.T) {
+	w := osfs.New(t.TempDir(), osfs.WithBoundOS())
+	dot, err := w.Chroot(GitDirName)
+	require.NoError(t, err)
+
+	s := filesystem.NewStorage(dot, cache.NewObjectLRUDefault())
+	r, err := Init(s, w)
+	require.NoError(t, err)
+	require.NotNil(t, r)
+
+	wt, err := r.Worktree()
+	require.NoError(t, err)
+	require.NotNil(t, wt)
+
+	file := "LICENSE"
+	f, err := w.OpenFile(file, os.O_CREATE|os.O_WRONLY, 0o666)
+	require.NoError(t, err)
+	require.NotNil(t, f)
+
+	content := []byte(strings.Repeat("a\n", 1000))
+	_, err = f.Write(content)
+	require.NoError(t, err)
+	err = f.Close()
+	require.NoError(t, err)
+
+	_, err = wt.Add(file)
+	require.NoError(t, err)
+
+	_, err = wt.Commit("add file", &CommitOptions{})
+	require.NoError(t, err)
+
+	st, err := wt.StatusWithOptions(StatusOptions{Strategy: Preload})
+	require.NoError(t, err)
+	assert.Equal(t,
+		&FileStatus{Worktree: Unmodified, Staging: Unmodified},
+		st.File(file))
+
+	// Make the file not regular. The same would apply to a transition
+	// from regular file to symlink.
+	err = os.Chmod(filepath.Join(w.Root(), file), 0o777)
+	require.NoError(t, err)
+
+	f, err = w.OpenFile(file, os.O_APPEND|os.O_RDWR, 0o777)
+	require.NoError(t, err)
+	require.NotNil(t, f)
+
+	_, err = f.Write([]byte("\n\n"))
+	require.NoError(t, err)
+	err = f.Close()
+	require.NoError(t, err)
+
+	_, err = wt.Add(file)
+	assert.NoError(t, err)
+
+	// go-git's Status diverges from "git status", so this check does not
+	// fail, even when the issue is present. As at this point "git status"
+	// reports the unstaged file was modified while "git diff" would return
+	// empty, as the files are the same but the index has the incorrect file
+	// size.
+	st, err = wt.StatusWithOptions(StatusOptions{Strategy: Preload})
+	assert.NoError(t, err)
+	assert.Equal(t,
+		&FileStatus{Worktree: Unmodified, Staging: Modified},
+		st.File(file))
+
+	idx, err := wt.r.Storer.Index()
+	assert.NoError(t, err)
+	require.NotNil(t, idx)
+	require.Len(t, idx.Entries, 1)
+
+	// Check whether the index was updated with the two new line breaks.
+	assert.Equal(t, uint32(len(content)+2), idx.Entries[0].Size)
+}