storage: filesystem, Add option to set a specific FS for alternates

Introduces the option to set a FS for alternates, enabling more flexible cross FS
sharing of alternates. If none is set, falls back to the current FS used for the
object storage.

The changes only process a given path once, and if an alternates dir is not valid,
exits with error - aligning behaviour with upstream.

Signed-off-by: Paulo Gomes <paulo.gomes@suse.com>

1 files changed, 125 insertions, 37 deletions

diff --git a/storage/filesystem/dotgit/dotgit_test.go b/storage/filesystem/dotgit/dotgit_test.go
index 1b6c113..2cbdb0c 100644
--- a/storage/filesystem/dotgit/dotgit_test.go
+++ b/storage/filesystem/dotgit/dotgit_test.go
@@ -6,6 +6,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"regexp"
 	"runtime"
 	"strings"
 	"testing"
@@ -15,6 +16,7 @@ import (
 	"github.com/go-git/go-billy/v5/util"
 	fixtures "github.com/go-git/go-git-fixtures/v4"
 	"github.com/go-git/go-git/v5/plumbing"
+	"github.com/stretchr/testify/assert"
 	. "gopkg.in/check.v1"
 )
 
@@ -810,53 +812,139 @@ func (s *SuiteDotGit) TestPackRefs(c *C) {
 	c.Assert(ref.Hash().String(), Equals, "b8d3ffab552895c19b9fcf7aa264d277cde33881")
 }
 
-func (s *SuiteDotGit) TestAlternates(c *C) {
-	fs, clean := s.TemporalFilesystem()
-	defer clean()
+func TestAlternatesDefault(t *testing.T) {
+	// Create a new dotgit object.
+	dotFS := osfs.New(t.TempDir())
 
-	// Create a new dotgit object and initialize.
-	dir := New(fs)
-	err := dir.Initialize()
-	c.Assert(err, IsNil)
+	testAlternates(t, dotFS, dotFS)
+}
 
-	// Create alternates file.
-	altpath := fs.Join("objects", "info", "alternates")
-	f, err := fs.Create(altpath)
-	c.Assert(err, IsNil)
+func TestAlternatesWithFS(t *testing.T) {
+	// Create a new dotgit object with a specific FS for alternates.
+	altFS := osfs.New(t.TempDir())
+	dotFS, _ := altFS.Chroot("repo2")
 
-	// Multiple alternates.
-	var strContent string
-	if runtime.GOOS == "windows" {
-		strContent = "C:\\Users\\username\\repo1\\.git\\objects\r\n..\\..\\..\\rep2\\.git\\objects"
-	} else {
-		strContent = "/Users/username/rep1//.git/objects\n../../../rep2//.git/objects"
+	testAlternates(t, dotFS, altFS)
+}
+
+func TestAlternatesWithBoundOS(t *testing.T) {
+	// Create a new dotgit object with a specific FS for alternates.
+	altFS := osfs.New(t.TempDir(), osfs.WithBoundOS())
+	dotFS, _ := altFS.Chroot("repo2")
+
+	testAlternates(t, dotFS, altFS)
+}
+
+func testAlternates(t *testing.T, dotFS, altFS billy.Filesystem) {
+	tests := []struct {
+		name      string
+		in        []string
+		inWindows []string
+		setup     func()
+		wantErr   bool
+		wantRoots []string
+	}{
+		{
+			name: "no alternates",
+		},
+		{
+			name:      "abs path",
+			in:        []string{filepath.Join(altFS.Root(), "./repo1/.git/objects")},
+			inWindows: []string{filepath.Join(altFS.Root(), ".\\repo1\\.git\\objects")},
+			setup: func() {
+				err := altFS.MkdirAll(filepath.Join("repo1", ".git", "objects"), 0o700)
+				assert.NoError(t, err)
+			},
+			wantRoots: []string{filepath.Join("repo1", ".git")},
+		},
+		{
+			name:      "rel path",
+			in:        []string{"../../../repo3//.git/objects"},
+			inWindows: []string{"..\\..\\..\\repo3\\.git\\objects"},
+			setup: func() {
+				err := altFS.MkdirAll(filepath.Join("repo3", ".git", "objects"), 0o700)
+				assert.NoError(t, err)
+			},
+			wantRoots: []string{filepath.Join("repo3", ".git")},
+		},
+		{
+			name:      "invalid abs path",
+			in:        []string{"/alt/target2"},
+			inWindows: []string{"\\alt\\target2"},
+			wantErr:   true,
+		},
+		{
+			name:      "invalid rel path",
+			in:        []string{"../../../alt/target3"},
+			inWindows: []string{"..\\..\\..\\alt\\target3"},
+			wantErr:   true,
+		},
 	}
-	content := []byte(strContent)
-	f.Write(content)
-	f.Close()
 
-	dotgits, err := dir.Alternates()
-	c.Assert(err, IsNil)
-	if runtime.GOOS == "windows" {
-		c.Assert(dotgits[0].fs.Root(), Equals, "C:\\Users\\username\\repo1\\.git")
-	} else {
-		c.Assert(dotgits[0].fs.Root(), Equals, "/Users/username/rep1/.git")
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			dir := NewWithOptions(dotFS, Options{AlternatesFS: altFS})
+			err := dir.Initialize()
+			assert.NoError(t, err)
+
+			content := strings.Join(tc.in, "\n")
+			if runtime.GOOS == "windows" {
+				content = strings.Join(tc.inWindows, "\r\n")
+			}
+
+			// Create alternates file.
+			altpath := dotFS.Join("objects", "info", "alternates")
+			f, err := dotFS.Create(altpath)
+			assert.NoError(t, err)
+			f.Write([]byte(content))
+			f.Close()
+
+			if tc.setup != nil {
+				tc.setup()
+			}
+
+			dotgits, err := dir.Alternates()
+			if tc.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+			}
+
+			for i, d := range dotgits {
+				assert.Regexp(t, "^"+regexp.QuoteMeta(altFS.Root()), d.fs.Root())
+				assert.Regexp(t, regexp.QuoteMeta(tc.wantRoots[i])+"$", d.fs.Root())
+			}
+		})
 	}
+}
 
-	// For relative path:
-	// /some/absolute/path/to/dot-git -> /some/absolute/path
-	pathx := strings.Split(fs.Root(), string(filepath.Separator))
-	pathx = pathx[:len(pathx)-2]
-	// Use string.Join() to avoid malformed absolutepath on windows
-	// C:Users\\User\\... instead of C:\\Users\\appveyor\\... .
-	resolvedPath := strings.Join(pathx, string(filepath.Separator))
-	// Append the alternate path to the resolvedPath
-	expectedPath := fs.Join(string(filepath.Separator), resolvedPath, "rep2", ".git")
+func TestAlternatesDupes(t *testing.T) {
+	dotFS := osfs.New(t.TempDir())
+	dir := New(dotFS)
+	err := dir.Initialize()
+	assert.NoError(t, err)
+
+	path := filepath.Join(dotFS.Root(), "target3")
+	dupes := []string{path, path, path, path, path}
+
+	content := strings.Join(dupes, "\n")
 	if runtime.GOOS == "windows" {
-		expectedPath = fs.Join(resolvedPath, "rep2", ".git")
+		content = strings.Join(dupes, "\r\n")
 	}
 
-	c.Assert(dotgits[1].fs.Root(), Equals, expectedPath)
+	err = dotFS.MkdirAll("target3", 0o700)
+	assert.NoError(t, err)
+
+	// Create alternates file.
+	altpath := dotFS.Join("objects", "info", "alternates")
+	f, err := dotFS.Create(altpath)
+	assert.NoError(t, err)
+	f.Write([]byte(content))
+	f.Close()
+
+	dotgits, err := dir.Alternates()
+	assert.NoError(t, err)
+	assert.Len(t, dotgits, 1)
 }
 
 type norwfs struct {