MinGW: fix stat() and lstat() implementations for handling symlinks

In msysGit the stat() function has been implemented using mingw_lstat
which sets the st_mode member to S_IFLNK when a symbolic links is found.
This causes the is_executable function to return when git attempts to
build a list of available commands in the help code and we end up missing
most git commands. (msysGit issue #445)

This patch modifies the implementation so that lstat() will return the link
flag but if we are called as stat() we read the size of the target and set
the mode to that of a regular file.

Includes squashed fix st_mode for symlink dirs

Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>
Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>

compat/mingw.c

@@ -192,8 +192,11 @@ static inline time_t filetime_to_time_t(const FILETIME *ft)
 /* We keep the do_lstat code in a separate function to avoid recursion.
  * When a path ends with a slash, the stat will fail with ENOENT. In
  * this case, we strip the trailing slashes and stat again.
+ *
+ * If follow is true then act like stat() and report on the link
+ * target. Otherwise report on the link itself.
  */
-static int do_lstat(const char *file_name, struct stat *buf)
+static int do_lstat(int follow, const char *file_name, struct stat *buf)
 {
 	WIN32_FILE_ATTRIBUTE_DATA fdata;
 
@@ -209,6 +212,25 @@ static int do_lstat(const char *file_name, struct stat *buf)
 		buf->st_atime = filetime_to_time_t(&(fdata.ftLastAccessTime));
 		buf->st_mtime = filetime_to_time_t(&(fdata.ftLastWriteTime));
 		buf->st_ctime = filetime_to_time_t(&(fdata.ftCreationTime));
+		if (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) {
+			WIN32_FIND_DATAA findbuf;
+			HANDLE handle = FindFirstFileA(file_name, &findbuf);
+			if (handle != INVALID_HANDLE_VALUE) {
+				if ((findbuf.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) &&
+						(findbuf.dwReserved0 == IO_REPARSE_TAG_SYMLINK)) {
+					if (follow) {
+						char buffer[MAXIMUM_REPARSE_DATA_BUFFER_SIZE];
+						buf->st_size = readlink(file_name, buffer, MAXIMUM_REPARSE_DATA_BUFFER_SIZE);
+					} else {
+						buf->st_mode = S_IFLNK;
+					}
+					buf->st_mode |= S_IREAD;
+					if (!(findbuf.dwFileAttributes & FILE_ATTRIBUTE_READONLY))
+						buf->st_mode |= S_IWRITE;
+				}
+				FindClose(handle);
+			}
+		}
 		return 0;
 	}
 	return -1;
@@ -220,12 +242,12 @@ static int do_lstat(const char *file_name, struct stat *buf)
  * complete. Note that Git stat()s are redirected to mingw_lstat()
  * too, since Windows doesn't really handle symlinks that well.
  */
-int mingw_lstat(const char *file_name, struct stat *buf)
+static int do_stat_internal(int follow, const char *file_name, struct stat *buf)
 {
 	int namelen;
 	static char alt_name[PATH_MAX];
 
-	if (!do_lstat(file_name, buf))
+	if (!do_lstat(follow, file_name, buf))
 		return 0;
 
 	/* if file_name ended in a '/', Windows returned ENOENT;
@@ -244,7 +266,16 @@ int mingw_lstat(const char *file_name, struct stat *buf)
 
 	memcpy(alt_name, file_name, namelen);
 	alt_name[namelen] = 0;
-	return do_lstat(alt_name, buf);
+	return do_lstat(follow, alt_name, buf);
+}
+
+int mingw_lstat(const char *file_name, struct stat *buf)
+{
+	return do_stat_internal(0, file_name, buf);
+}
+int mingw_stat(const char *file_name, struct stat *buf)
+{
+	return do_stat_internal(1, file_name, buf);
 }
 
 #undef fstat

compat/mingw.h

@@ -235,10 +235,11 @@ int mingw_getpagesize(void);
 #ifndef ALREADY_DECLARED_STAT_FUNCS
 #define stat _stati64
 int mingw_lstat(const char *file_name, struct stat *buf);
+int mingw_stat(const char *file_name, struct stat *buf);
 int mingw_fstat(int fd, struct stat *buf);
 #define fstat mingw_fstat
 #define lstat mingw_lstat
-#define _stati64(x,y) mingw_lstat(x,y)
+#define _stati64(x,y) mingw_stat(x,y)
 #endif
 
 int mingw_utime(const char *file_name, const struct utimbuf *times);