Add ability to set a lockfile for a run about sql-runner HOT 5 CLOSED

Bringing forwards...

from sql-runner.

Some lock rules:

• If the lock file cannot be written, die with something like "Lock file $foo is not writable. Cannot start"
• If the lock file is already found, die with something like "SQL Runner $foo found, previous run failed or is ongoing. Cannot start"

From a Factotum perspective, it's nice for "lock file already found" to have a distinct return code, because Factotum DAGs will often want to treat that as a no-op rather than a failure.

from sql-runner.

Note that the -dryRun should not check locks, nor set them...

from sql-runner.

What exit code would you like for lock file already found @alexanderdean ?

from sql-runner.

Hmm, per http://tldp.org/LDP/abs/html/exitcodes.html maybe 3?

from sql-runner.