compat/mingw.c: Teach mingw_rename() to replace read-only files

On POSIX, rename() can replace files that are not writable. On Windows,
however, read-only files cannot be replaced without additional efforts:
We have to make the destination writable first.

Since the situations where the destination is read-only are rare, we do not
make the destination writable on every invocation, but only if the first
try to rename a file failed with an "access denied" error.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/compat/mingw.c b/compat/mingw.c
index 772cad510d5d260fdf33b4f7d6ff79f9f3367b05..45733f9e04eb87409a896898cb5a92b37e87a920 100644 (file)
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -865,6 +865,8 @@ int mingw_connect(int sockfd, struct sockaddr *sa, size_t sz)
 #undef rename
 int mingw_rename(const char *pold, const char *pnew)
 {
+       DWORD attrs;
+
        /*
         * Try native rename() first to get errno right.
         * It is based on MoveFile(), which cannot overwrite existing files.
@@ -876,12 +878,19 @@ int mingw_rename(const char *pold, const char *pnew)
        if (MoveFileEx(pold, pnew, MOVEFILE_REPLACE_EXISTING))
                return 0;
        /* TODO: translate more errors */
-       if (GetLastError() == ERROR_ACCESS_DENIED) {
-               DWORD attrs = GetFileAttributes(pnew);
-               if (attrs != INVALID_FILE_ATTRIBUTES && (attrs & FILE_ATTRIBUTE_DIRECTORY)) {
+       if (GetLastError() == ERROR_ACCESS_DENIED &&
+           (attrs = GetFileAttributes(pnew)) != INVALID_FILE_ATTRIBUTES) {
+               if (attrs & FILE_ATTRIBUTE_DIRECTORY) {
                        errno = EISDIR;
                        return -1;
                }
+               if ((attrs & FILE_ATTRIBUTE_READONLY) &&
+                   SetFileAttributes(pnew, attrs & ~FILE_ATTRIBUTE_READONLY)) {
+                       if (MoveFileEx(pold, pnew, MOVEFILE_REPLACE_EXISTING))
+                               return 0;
+                       /* revert file attributes on failure */
+                       SetFileAttributes(pnew, attrs);
+               }
        }
        errno = EACCES;
        return -1;