doc add: renormalize is not idempotent for CRCRLF

Bug report
 https://lore.kernel.org/git/AM0PR02MB56357CC96B702244F3271014E8DC9@AM0PR02MB5635.eurprd02.prod.outlook.com/
noted that a file containing /r/r/n needed renormalising twice.

This is by design. Lone CR characters, not paired with an LF, are left
unchanged. Note the lack of idempotentness of the "clean" filter in the
documentation.

Renormalize was introduced at 9472935 (add: introduce "--renormalize",
Torsten Bögershausen, 2017-11-16)

Signed-off-by: Philip Oakley <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: PhilipOakley

Documentation/git-add.txt

@@ -188,7 +188,8 @@ for "git add --no-all <pathspec>...", i.e. ignored removed files.
 	forcibly add them again to the index.  This is useful after
 	changing `core.autocrlf` configuration or the `text` attribute
 	in order to correct files added with wrong CRLF/LF line endings.
-	This option implies `-u`.
+	This option implies `-u`. Lone CR characters are untouched, so
+	cleaning not idempotent. A CRCRLF sequence cleans to CRLF.
 
 --chmod=(+|-)x::
 	Override the executable bit of the added files.  The executable