Localize shell variable REPLY to avoid overwriting users' value

[akinomyoga]

The shell function __python_argcomplete_scan_head in the completion setting (argcomplete/bash_completion.d/_python-argcomplete) uses the read builtin without specifying variable names. This stores the read result in the shell variable REPLY. Then, __python_argcomplete_scan_head checks the value of REPLY. A problem is that this will clobber the users' values of the global shell variable REPLY on an attempt of completion. We should declare the REPLY as a local variable in the shell function __python_argcomplete_scan_head.

[kislyuk]

Thanks!

[akinomyoga]

Thank you!