script to automate binary search for regression

[Janis Johnson <janis187 at us dot ibm dot com>]

Here's the script I'm using to do binary searches to locate regressions.
It invokes separate scripts to do the real work: update CVS, build GCC,
and run the test.  It starts with two specified dates and calls the
user-provided scripts in a binary search to narrow the time range where
the test behaviour changed to a specified time range, one hour by
default.  There are no restrictions on the starting dates, they just
need to be recognized by the date command.  It uses an extension in GNU
date to convert a date to seconds from the epoch, but on a system where
GNU date isn't an option that part could be replaced by a small C
program to do the conversion.

Since you provide the other scripts, they can do whatever you want: use
a CVS branch, build only cc1plus or do a full bootstrap, and whatever it
takes to run the test.

The length of the script is mostly due to comments and lots of error
checking.  I've tested it fairly thoroughly.  If you find this helpful,
let me know and I'll ask about adding it to contrib.

Janis Johnson
IBM Linux Technology Center

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