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 this limitation 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]>
Reviewed-by: Torsten Bögershausen <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: PhilipOakley

Documentation/git-add.txt

@@ -188,7 +188,9 @@ 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, thus
+	while a CRLF cleans to LF, a CRCRLF sequence is only partially
+	cleaned to CRLF.
 
 --chmod=(+|-)x::
 	Override the executable bit of the added files.  The executable