win32: map windows error codes to errno

Introduce mapping from windows error codes to errno values.  This
allows us to replace our calls to the Windows posix emulation functions
with calls to the Win32 APIs for more fine-grained control over the
emulation.

These mappings match the Windows CRT's mappings for its posix emulation
as they were described to me.

src/win32/posix_w32.c

@@ -44,6 +44,119 @@
 /* GetFinalPathNameByHandleW signature */
 typedef DWORD(WINAPI *PFGetFinalPathNameByHandleW)(HANDLE, LPWSTR, DWORD, DWORD);
 
+GIT_INLINE(void) set_errno(void)
+{
+	switch (GetLastError()) {
+	case ERROR_FILE_NOT_FOUND:
+	case ERROR_PATH_NOT_FOUND:
+	case ERROR_INVALID_DRIVE:
+	case ERROR_NO_MORE_FILES:
+	case ERROR_BAD_NETPATH:
+	case ERROR_BAD_NET_NAME:
+	case ERROR_BAD_PATHNAME:
+	case ERROR_FILENAME_EXCED_RANGE:
+		errno = ENOENT;
+		break;
+	case ERROR_BAD_ENVIRONMENT:
+		errno = E2BIG;
+		break;
+	case ERROR_BAD_FORMAT:
+	case ERROR_INVALID_STARTING_CODESEG:
+	case ERROR_INVALID_STACKSEG:
+	case ERROR_INVALID_MODULETYPE:
+	case ERROR_INVALID_EXE_SIGNATURE:
+	case ERROR_EXE_MARKED_INVALID:
+	case ERROR_BAD_EXE_FORMAT:
+	case ERROR_ITERATED_DATA_EXCEEDS_64k:
+	case ERROR_INVALID_MINALLOCSIZE:
+	case ERROR_DYNLINK_FROM_INVALID_RING:
+	case ERROR_IOPL_NOT_ENABLED:
+	case ERROR_INVALID_SEGDPL:
+	case ERROR_AUTODATASEG_EXCEEDS_64k:
+	case ERROR_RING2SEG_MUST_BE_MOVABLE:
+	case ERROR_RELOC_CHAIN_XEEDS_SEGLIM:
+	case ERROR_INFLOOP_IN_RELOC_CHAIN:
+		errno = ENOEXEC;
+		break;
+	case ERROR_INVALID_HANDLE:
+	case ERROR_INVALID_TARGET_HANDLE:
+	case ERROR_DIRECT_ACCESS_HANDLE:
+		errno = EBADF;
+		break;
+	case ERROR_WAIT_NO_CHILDREN:
+	case ERROR_CHILD_NOT_COMPLETE:
+		errno = ECHILD;
+		break;
+	case ERROR_NO_PROC_SLOTS:
+	case ERROR_MAX_THRDS_REACHED:
+	case ERROR_NESTING_NOT_ALLOWED:
+		errno = EAGAIN;
+		break;
+	case ERROR_ARENA_TRASHED:
+	case ERROR_NOT_ENOUGH_MEMORY:
+	case ERROR_INVALID_BLOCK:
+	case ERROR_NOT_ENOUGH_QUOTA:
+		errno = ENOMEM;
+		break;
+	case ERROR_ACCESS_DENIED:
+	case ERROR_CURRENT_DIRECTORY:
+	case ERROR_WRITE_PROTECT:
+	case ERROR_BAD_UNIT:
+	case ERROR_NOT_READY:
+	case ERROR_BAD_COMMAND:
+	case ERROR_CRC:
+	case ERROR_BAD_LENGTH:
+	case ERROR_SEEK:
+	case ERROR_NOT_DOS_DISK:
+	case ERROR_SECTOR_NOT_FOUND:
+	case ERROR_OUT_OF_PAPER:
+	case ERROR_WRITE_FAULT:
+	case ERROR_READ_FAULT:
+	case ERROR_GEN_FAILURE:
+	case ERROR_SHARING_VIOLATION:
+	case ERROR_LOCK_VIOLATION:
+	case ERROR_WRONG_DISK:
+	case ERROR_SHARING_BUFFER_EXCEEDED:
+	case ERROR_NETWORK_ACCESS_DENIED:
+	case ERROR_CANNOT_MAKE:
+	case ERROR_FAIL_I24:
+	case ERROR_DRIVE_LOCKED:
+	case ERROR_SEEK_ON_DEVICE:
+	case ERROR_NOT_LOCKED:
+	case ERROR_LOCK_FAILED:
+		errno = EACCES;
+		break;
+	case ERROR_FILE_EXISTS:
+	case ERROR_ALREADY_EXISTS:
+		errno = EEXIST;
+		break;
+	case ERROR_NOT_SAME_DEVICE:
+		errno = EXDEV;
+		break;
+	case ERROR_INVALID_FUNCTION:
+	case ERROR_INVALID_ACCESS:
+	case ERROR_INVALID_DATA:
+	case ERROR_INVALID_PARAMETER:
+	case ERROR_NEGATIVE_SEEK:
+		errno = EINVAL;
+		break;
+	case ERROR_TOO_MANY_OPEN_FILES:
+		errno = EMFILE;
+		break;
+	case ERROR_DISK_FULL:
+		errno = ENOSPC;
+		break;
+	case ERROR_BROKEN_PIPE:
+		errno = EPIPE;
+		break;
+	case ERROR_DIR_NOT_EMPTY:
+		errno = ENOTEMPTY;
+		break;
+	default:
+		errno = EINVAL;
+	}
+}
+
 /**
  * Truncate or extend file.
  *