Merge branch 'js/bs-is-a-dir-sep-on-windows' into maint

"foo\bar\baz" in "git fetch foo\bar\baz", even though there is no
slashes in it, cannot be a nickname for a remote on Windows, as
that is likely to be a pathname on a local filesystem.

* js/bs-is-a-dir-sep-on-windows:
  Windows: do not treat a path with backslashes as a remote's nick name
  mingw.h: permit arguments with side effects for is_dir_sep

Author: gitster

compat/mingw.h

@@ -398,7 +398,11 @@ HANDLE winansi_get_osfhandle(int fd);
 	(isalpha(*(path)) && (path)[1] == ':' ? 2 : 0)
 int mingw_skip_dos_drive_prefix(char **path);
 #define skip_dos_drive_prefix mingw_skip_dos_drive_prefix
-#define is_dir_sep(c) ((c) == '/' || (c) == '\\')
+static inline int mingw_is_dir_sep(int c)
+{
+	return c == '/' || c == '\\';
+}
+#define is_dir_sep mingw_is_dir_sep
 static inline char *mingw_find_last_dir_sep(const char *path)
 {
 	char *ret = NULL;

remote.c

@@ -649,7 +649,12 @@ static int valid_remote_nick(const char *name)
 {
 	if (!name[0] || is_dot_or_dotdot(name))
 		return 0;
-	return !strchr(name, '/'); /* no slash */
+
+	/* remote nicknames cannot contain slashes */
+	while (*name)
+		if (is_dir_sep(*name++))
+			return 0;
+	return 1;
 }
 
 const char *remote_for_branch(struct branch *branch, int *explicit)