data_sync: sync homedir to external storage.

cmd/data_sync/README

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+data_sync
+
+This is a tool I wrote primarily to sync my home directory to a backup drive plugged
+into my laptop. This system is provisioned by Ansible, and the goal is to be able to
+just copy my home directory back in the event of a failure without having lost a great
+deal of work. Specifically, I use a Framework laptop with the 1TB storage module,
+encrypted with LUKS, and run this twice daily (timed to correspond with my commute,
+though that's not really necessary). It started off as a shell script, then I decided
+to just write it as a program.
+
+Usage: data_sync [-d path] [-l level] [-m path] [-nqsv]
+                                  [-t path]
+        -d path         path to sync source directory
+                        (default "~")
+        -l level        log level to output (default "INFO"). Valid log
+                        levels are DEBUG, INFO, NOTICE, WARNING, ERR,
+                        CRIT, ALERT, EMERG. The default is INFO.
+        -m path         path to sync mount directory
+                        (default "/media/$USER/$(hostname -s)_data")
+        -n              dry-run mode: only check paths and print files to
+                        exclude
+        -q              suppress console output
+        -s              suppress syslog output
+        -t path         path to sync target directory
+                        (default "/media/$USER/$(hostname -s)_data/$USER")
+        -v              verbose rsync output
+
+data_sync rsyncs the tree at the sync source directory (-d) to the sync target
+directory (-t); it checks the mount directory (-m) exists; the sync target
+target directory must exist on the mount directory.
+