This has been wrong since bbbdf0478e, but the race condition was not
previously been (often?) triggered in the tests. With the DB_RETRY_LOCK
patches, it manifests itself as a deadlock.
The files (test) scripts source (with builtin command `.`) provides
information which the scripts depend, and without the `source` to
succeed allowing script to continue may lead to dangerous situations
(e.g. rm -rf "${undefined_variable}"/*).
At the end of all source (.) lines construct ' || exit 1' was added;
In our case the script script will exit if it cannot find (or read) the
file to be sourced. Additionally script would also exits if the last
command of the sourced file exited nonzero.
The main goal is to support gzipped output for future internal
calls (e.g. from notmuch-new) to notmuch_database_dump.
The additional dependency is not very heavy since xapian already pulls
in zlib.
We want the dump to be "atomic", in the sense that after running the
dump file is either present and complete, or not present. This avoids
certain classes of mishaps involving overwriting a good backup with a
bad or partial one.
All test scripts to be executed are now named as T\d\d\d-name.sh,
numers in increments of 10.
This eases adding new tests and developers to see which are test scripts
that are executed by test suite and in which order.
