config --show-origin: report paths with forward slashes

On Windows, the backslash is the native directory separator, but all
supported Windows versions also accept the forward slash in most
circumstances.

Our tests expect forward slashes.

Relative paths are generated by Git using forward slashes.

So let's try to be consistent and use forward slashes in the $HOME part
of the paths reported by `git config --show-origin`, too.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/mingw.h

@@ -396,6 +396,12 @@ static inline char *mingw_find_last_dir_sep(const char *path)
 			ret = (char *)path;
 	return ret;
 }
+static inline void convert_slashes(char *path)
+{
+	for (; *path; path++)
+		if (*path == '\\')
+			*path = '/';
+}
 #define find_last_dir_sep mingw_find_last_dir_sep
 int mingw_offset_1st_component(const char *path);
 #define offset_1st_component mingw_offset_1st_component

path.c

@@ -584,6 +584,9 @@ char *expand_user_path(const char *path)
 			if (!home)
 				goto return_null;
 			strbuf_addstr(&user_path, home);
+#ifdef GIT_WINDOWS_NATIVE
+			convert_slashes(user_path.buf);
+#endif
 		} else {
 			struct passwd *pw = getpw_str(username, username_len);
 			if (!pw)