mention use of "hooks.allownonascii" in "man githooks"

The default pre-commit script checks the config variable
"hooks.allownonascii" to determine whether to allow non-ASCII file
names -- mention this in "man githooks", just as the section on
"update" mentions the use of "hooks.allowunannotated".

Signed-off-by: Robert P. J. Day <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: robertpjday

Documentation/githooks.txt

@@ -99,6 +99,10 @@ All the `git commit` hooks are invoked with the environment
 variable `GIT_EDITOR=:` if the command will not bring up an editor
 to modify the commit message.
 
+The default 'pre-commit' hook, when enabled--and with the
+`hooks.allownonascii` config option unset or set to false--prevents
+the use of non-ASCII filenames.
+
 prepare-commit-msg
 ~~~~~~~~~~~~~~~~~~