on-modify.timewarrior: Use last annotation as additional tag, if present

[fdcds]

This allows the following workflow to be effective and tracked in a useful manner:

task 123 start First draft
task 123 stop
...
task 123 start Second iteration
task 123 stop
...
task 123 start Bugfixing
task 123 stop
...

This will be tracked as:

01:00 - 02:00 <TASK 123 TAGS> "First draft"
03:00 - 04:00 <TASK 123 TAGS> "Second iteration"
05:00 - 06:00 <TASK 123 TAGS> "Bugfixing"

[lauft]

The problem I see here is that this creates a lot of new tags (which are only used once).
Timewarrior 1.2.0 has a command annotate which allows to store an extra string along with the interval.

[ChargingBulle]

Oh I never use a limited number of tags. I use TimeWarrior like this:

inc 20190912T100000Z - 20190912T110000Z # "Investigated issue 123" cooltool dev
inc 20190912T110000Z - 20190912T111500Z # "Fixed issue 123" cooltool dev
inc 20190912T111500Z - 20190912T130000Z # "Upgrading WSL, borking my ethernet setup while doing so" dev

The TaskWarrior integration incentivises an usage like this.
That's why I think this enhancement might be really cool (with config toggle).

[xeruf]

The problem I see here is that this creates a lot of new tags (which are only used once).
reports

As @JavaZauber mentioned, this happens already with descriptions, so the argument is hardly valid.
We need to solve #41/#209/#179 anyways, and then this won't be a problem anymore either.

[lauft]

Migrated to GothenburgBitFactory/task-timewarrior-hook#4

Please continue any discussion of this PR there.