Documentation/git-status: mention how to detect copies

The man page documents that git-status can find copies, but does not
mention how. Whereas git-diff has command line options -C, there is
no such option for git-status - it will only detect copies when the
"status.renames" config option is "copies" or "copy". Document that
in git-status.txt because this has confused me and others[1].

[1]: https://www.reddit.com/r/git/comments/ppc2l9/how_to_get_a_file_with_copied_status/

Signed-off-by: Johannes Altmanninger <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: krobelus

Documentation/git-status.txt

@@ -211,7 +211,7 @@ show tracked paths:
 * 'A' = added
 * 'D' = deleted
 * 'R' = renamed
-* 'C' = copied
+* 'C' = copied (if config option status.renames is set to "copies")
 * 'U' = updated but unmerged
 
 ....