RFR: 8042810: (s) hgforest: some shells run read in sub-shell and can't use fifo

[Chris Hegarty]

Looks fine to me Mike.

Trivially while you are there (not related to your changes), or i can do it separately, --sequentially now runs with up to two parallel commands. 

-Chris

> On 9 May 2014, at 03:19, Mike Duigou <mike.duigou at oracle.com> wrote:
> 
> Hello all;
> 
> This issue is a follow-on bug fix to JDK-8041151 (Improve hgforest.sh concurrency). That changeset introduced use of fifos for monitoring sub-shell completion and included an alternative implementation for configurations which did not properly support fifos. This changeset detects another unsupported configuration, older shells which run the "read" command using a sub-shell.
> 
> I've tested the change on Solaris 10u11, Solaris 11u1, Ubuntu Linux 13.10 x64, MacOS 10.9. Of these only the Bash 3.2 shell on Solaris 10u11 does not support FIFOs. I have not tested this specific change on Cygwin as FIFOs were already disabled on Cygwin.
> 
> https://bugs.openjdk.java.net/browse/JDK-8042810
> http://cr.openjdk.java.net/~mduigou/JDK-8042810/0/webrev/
> 
> Mike