Windows: allow using UNC path for git repository

[efl: moved MinGW-specific part to compat/]
[jes: fixed compilation on non-Windows]

Eric Sunshine fixed mingw_offset_1st_component() to return
consistently "foo" for UNC "//machine/share/foo", cf

http://groups.google.com/group/msysgit/browse_thread/thread/c0af578549b5dda0

Author: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Cezary Zawadka <czawadka@gmail.com>
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Stepan Kasal <kasal@ucw.cz>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/compat/mingw.c b/compat/mingw.c
index e9892f8..a0e13bc 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -1823,3 +1823,27 @@
 	errno = EINVAL;
 	return -1;
 }
+
+int mingw_offset_1st_component(const char *path)
+{
+	int offset = 0;
+	if (has_dos_drive_prefix(path))
+		offset = 2;
+
+	/* unc paths */
+	else if (is_dir_sep(path[0]) && is_dir_sep(path[1])) {
+
+		/* skip server name */
+		char *pos = strpbrk(path + 2, "\\/");
+		if (!pos)
+			return 0; /* Error: malformed unc path */
+
+		do {
+			pos++;
+		} while (*pos && !is_dir_sep(*pos));
+
+		offset = pos - path;
+	}
+
+	return offset + is_dir_sep(path[offset]);
+}