* Only update the database if the item modified time is different, otherwise we are needlessly updating the database with data that is the same
* Generating a file hash, during the file integrity check is computationally expensive. Only generate a file hash if the modified time of the file is different, otherwise it is pointless to generate the file hash during each integrity check
* Only flush SHM and WAL post integrity check
* Implement a check to validate local filesystem available space before attempting file download
* Implement 'space_reservation' config option with a default value of 50 MB
* Prevent the original run-away logging error message 'Failed initialization on handle XXXX' from occurring if the system is out of space
* Update documentation and man page
* Update to dmd-2.088.0 and ldc-1.18.0
* Update documentation based on change in DMD and LDC minimum versions. Minimum DMD version now 2.088.0 and minimum LDC version now 1.18.0.
* Security upgrade alpine Docker file to 3.16
* Fix where if the --confdir as specified has incorrect parent permissions, the client is unable to read the required hash files, thus cause an application crash
* When opening files, we should only be opening them as read-only
* When we write out any hash files. they should only be readable|writeable by the userid that is running the application
* Force a synchronization of a specific folder, only when using --synchronize --single-directory and ignoring all non-default skip_dir and skip_file rules
* When using the application with 'defaults' with logging enabled and no verbose mode, the application output that a sync process has started & finished is only written to the logfile every 5 sync times (25 mins). This change updates this so that, if defaults are being used with logging enabled and no verbose mode, the application will always, at a minimum, write out to the application log file when a sync was started and when it was completed. This provides important reference in the log as to when an activity began and was completed.
* In some scenarios users may have a running background service syncing data (systemd or otherwise). In these events, running the application in standalone mode can create a conflict when attempting to perform database queries when there are significant changes to data structures occurring. This PR specifically checks if the database operation files are present, and, if these are present (meaning the application is most likely currently operational) fail fast and not execute the application as a second instance against the same active configuration.
Potentially also resolves RBZ2061430 and RBZ2075468