win32: name the dummy union in GIT_REPARSE_DATA_BUFFER

Instead of buf->"typeofbuffer"ReparseBuffer the members will be
referenced with buf->ReparseBuffer."typeofbuffer"

https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/ntifs/ns-ntifs-_reparse_data_buffer?redirectedfrom=MSDN
calls the union DUMMYUNIONNAME but that looks a bit cluttered.

Author: boretrk

src/win32/path_w32.c

@@ -381,14 +381,14 @@ int git_win32_path_readlink_w(git_win32_path dest, const git_win32_path path)
 
 	switch (reparse_buf->ReparseTag) {
 	case IO_REPARSE_TAG_SYMLINK:
-		target = reparse_buf->SymbolicLinkReparseBuffer.PathBuffer +
-			(reparse_buf->SymbolicLinkReparseBuffer.SubstituteNameOffset / sizeof(WCHAR));
-		target_len = reparse_buf->SymbolicLinkReparseBuffer.SubstituteNameLength / sizeof(WCHAR);
+		target = reparse_buf->ReparseBuffer.SymbolicLink.PathBuffer +
+			(reparse_buf->ReparseBuffer.SymbolicLink.SubstituteNameOffset / sizeof(WCHAR));
+		target_len = reparse_buf->ReparseBuffer.SymbolicLink.SubstituteNameLength / sizeof(WCHAR);
 	break;
 	case IO_REPARSE_TAG_MOUNT_POINT:
-		target = reparse_buf->MountPointReparseBuffer.PathBuffer +
-			(reparse_buf->MountPointReparseBuffer.SubstituteNameOffset / sizeof(WCHAR));
-		target_len = reparse_buf->MountPointReparseBuffer.SubstituteNameLength / sizeof(WCHAR);
+		target = reparse_buf->ReparseBuffer.MountPoint.PathBuffer +
+			(reparse_buf->ReparseBuffer.MountPoint.SubstituteNameOffset / sizeof(WCHAR));
+		target_len = reparse_buf->ReparseBuffer.MountPoint.SubstituteNameLength / sizeof(WCHAR);
 	break;
 	default:
 		errno = EINVAL;

src/win32/reparse.h

@@ -26,18 +26,18 @@ typedef struct _GIT_REPARSE_DATA_BUFFER {
 			USHORT PrintNameLength;
 			ULONG  Flags;
 			WCHAR  PathBuffer[1];
-		} SymbolicLinkReparseBuffer;
+		} SymbolicLink;
 		struct {
 			USHORT SubstituteNameOffset;
 			USHORT SubstituteNameLength;
 			USHORT PrintNameOffset;
 			USHORT PrintNameLength;
 			WCHAR  PathBuffer[1];
-		} MountPointReparseBuffer;
+		} MountPoint;
 		struct {
 			UCHAR DataBuffer[1];
-		} GenericReparseBuffer;
-	};
+		} Generic;
+	} ReparseBuffer;
 } GIT_REPARSE_DATA_BUFFER;
 
 #define REPARSE_DATA_HEADER_SIZE			8

tests/core/link.c

@@ -123,7 +123,7 @@ static void do_junction(const char *old, const char *new)
 	reparse_buf = LocalAlloc(LMEM_FIXED|LMEM_ZEROINIT, reparse_buflen);
 	cl_assert(reparse_buf);
 
-	subst_utf16 = reparse_buf->MountPointReparseBuffer.PathBuffer;
+	subst_utf16 = reparse_buf->ReparseBuffer.MountPoint.PathBuffer;
 	print_utf16 = subst_utf16 + subst_utf16_len + 1;
 
 	ret = git__utf8_to_16(subst_utf16, subst_utf16_len + 1,
@@ -135,10 +135,10 @@ static void do_junction(const char *old, const char *new)
 	cl_assert_equal_i(print_utf16_len, ret);
 
 	reparse_buf->ReparseTag = IO_REPARSE_TAG_MOUNT_POINT;
-	reparse_buf->MountPointReparseBuffer.SubstituteNameOffset = 0;
-	reparse_buf->MountPointReparseBuffer.SubstituteNameLength = subst_byte_len;
-	reparse_buf->MountPointReparseBuffer.PrintNameOffset = (USHORT)(subst_byte_len + sizeof(WCHAR));
-	reparse_buf->MountPointReparseBuffer.PrintNameLength = print_byte_len;
+	reparse_buf->ReparseBuffer.MountPoint.SubstituteNameOffset = 0;
+	reparse_buf->ReparseBuffer.MountPoint.SubstituteNameLength = subst_byte_len;
+	reparse_buf->ReparseBuffer.MountPoint.PrintNameOffset = (USHORT)(subst_byte_len + sizeof(WCHAR));
+	reparse_buf->ReparseBuffer.MountPoint.PrintNameLength = print_byte_len;
 	reparse_buf->ReparseDataLength = reparse_buflen - REPARSE_DATA_HEADER_SIZE;
 
 	cl_win32_pass(DeviceIoControl(handle, FSCTL_SET_REPARSE_POINT,