fix: ensure globbed FileInfo always has correct size (#482)

When globbing a file that has a FileInfo set, we would reuse the pointer
to the original file's FileInfo even if the matched files' sizes are
different, causing deb to error when writing the data file due to
mismatching sizes.

Copy the FileInfo and recalculate its size when globbing. Add a test
case to check this scenario.

Fixes #316.

files/files.go

@@ -177,11 +177,18 @@ func ExpandContentGlobs(contents Contents, disableGlobbing bool) (files Contents
 
 func appendGlobbedFiles(all Contents, globbed map[string]string, origFile *Content) (Contents, error) {
 	for src, dst := range globbed {
+		// if the file has a FileInfo, we need to copy it but recalculate its size
+		newFileInfo := origFile.FileInfo
+		if newFileInfo != nil {
+			newFileInfoVal := *newFileInfo
+			newFileInfoVal.Size = 0
+			newFileInfo = &newFileInfoVal
+		}
 		newFile := (&Content{
 			Destination: ToNixPath(dst),
 			Source:      ToNixPath(src),
 			Type:        origFile.Type,
-			FileInfo:    origFile.FileInfo,
+			FileInfo:    newFileInfo,
 			Packager:    origFile.Packager,
 		}).WithFileInfoDefaults()
 		if dst, err := os.Readlink(src); err == nil {

files/files_test.go

@@ -347,3 +347,26 @@ func TestGlobbingWhenFilesHaveBrackets(t *testing.T) {
 		}
 	}
 }
+
+func TestGlobbingFilesWithDifferentSizesWithFileInfo(t *testing.T) {
+	result, err := files.ExpandContentGlobs(files.Contents{
+		{
+			Source:      "./testdata/globtest/different-sizes/**/*",
+			Destination: ".",
+			FileInfo: &files.ContentFileInfo{
+				Mode: 0o777,
+			},
+		},
+	}, false)
+	if err != nil {
+		t.Fatalf("expand content globs: %v", err)
+	}
+
+	if len(result) != 2 {
+		t.Fatalf("unexpected result length: %d, expected 2", len(result))
+	}
+
+	if result[0].FileInfo.Size == result[1].FileInfo.Size {
+		t.Fatal("test FileInfos have the same size, expected different")
+	}
+}

files/testdata/globtest/different-sizes/a/a.txt

@@ -0,0 +1 @@
+foo

files/testdata/globtest/different-sizes/b/b.txt

@@ -0,0 +1 @@
+barbaz