Add clocktable formatter to filter entries with small clocking time

Whenever I try to check what I actually in the past couple of days, I
try to use a clocktable for this.  However, those clocktables are
usually littered with small entries, i.e. entries where I only spent a
couple of minutes on (example: a quick chat with a colleague).  Those
entries clutter the view for the relevant entries, making it hard to
make sense of past activities.

Restricting the clocktable to a certain depth somehow helps, but major
single tasks are hidden this way, and I usually want to see those.

The custom formatter added in this commit tries to alleviate this
situation by providing a mechanism to filter out those entries using a
minimum clocktime threshold.  Let's see how this feature plays out.

init.el

@@ -548,6 +548,7 @@
              db/org-cleanup-continuous-clocks
              db/find-csv-in-org
              db/org-mark-current-default-task
+             db/org-clocktable-write-with-threshold
              db/export-diary
              db/org-insert-checklist
              db/org-copy-body-from-item-to-point

site-lisp/db-org.el

@@ -518,6 +518,31 @@ Work task and home task are determined by the current values of
         (message "Setting default task to: %s" (org-link-display-format (org-entry-get (point) "ITEM")))
         (org-clock-mark-default-task)))))
 
+(defun db/org-clocktable-write-with-threshold (ipos tables params)
+  "A clocktable formatter to filter entries by minimal clock time.
+
+The arguments IPOS, TABLES, and PARAMS are as for the default
+clocktable formatter `org-clocktable-write-default'.  The only
+difference is that PARAMS may include an additional property
+called `:clocktime-treshold' with a non-negative integer value.
+If such a value is given, each table entry in TABLES whose TIME
+value is below this threshold is removed before formatting the
+clocktable (see `org-clock-get-table-data' for the meaning of
+TIME)."
+  (let ((tables tables))                ; necessary?
+    (when-let ((threshold (plist-get params :clocktime-threshold)))
+      (unless (and (integerp threshold) (>= threshold 0))
+        (user-error "Clocktime threshold must be a non-negative integer, but is %s"
+                    threshold))
+      (setq tables (-map (pcase-lambda (`(,file-name ,file-time ,entries))
+                           (list file-name
+                                 file-time
+                                 (-filter (pcase-lambda (`(_ _ _ _ ,time _))
+                                            (>= time threshold))
+                                          entries)))
+                         tables)))
+    (org-clocktable-write-default ipos tables params)))
+
 
 ;;; Workload Reports