taskwarrior: Add conditional tasksh invocation

To use taskwarrior, an alias to `t` has been created. If you invoke any
taskwarrior command through `t`, it will behave just as taskwarrior
would (just with a shorter name).
If you invoke `t` without any additional arguments, it will instead open
up the tasksh program and let you play around in there.

taskwarrior/.config/sh/alias.d/taskwarrior.sh

@@ -1,4 +1,14 @@
 #!/usr/bin/env sh
 
-alias t="tasksh"
 alias taskopen='taskopen -c ${XDG_DATA_HOME}/task/notes'
+
+# invoking t starts the task shell
+# passing arguments along passes them straight through to taskwarrior instead
+t() {
+  # check for existence of tasksh before doing this whole song and dance
+  if type tasksh >/dev/null 2>&1 && [ "$#" -eq 0 ]; then
+    tasksh
+  else
+    task "$@"
+  fi
+}