4.3. Retrace and reenact¶
“Thanks a lot for sharing your dataset with me! This is super helpful. I’m sure I’ll catch up in no time!”, your room mate says confidently. “How far did you get with the DataLad commands yet?” he asks at last.
“Mhh, I think the last big one was datalad run. Actually, let me quickly show you what this command does. There is something that I’ve been wanting to try anyway.” you say.
The dataset you shared contained a number of datalad run
commands. For example, you created the simple podcasts.tsv
file that listed all titles and speaker names of the longnow
podcasts.
Given that you learned to create “proper” datalad run commands,
complete with --input
and --output
specification,
anyone should be able to datalad rerun these commits
easily. This is what you want to try now.
You begin to think about which datalad run commit would be
the most useful one to take a look at. The creation of
podcasts.tsv
was a bit dull – at this point in time, you
didn’t yet know about --input
and --output
arguments,
and the resulting output is present anyway because text files
like this .tsv
file are stored in Git.
However, one of the attempts to resize a picture could be
useful. The input, the podcast logos, is not yet retrieved,
nor is the resulting, resized image. “Let’s go for this!”,
you say, and drag your confused room mate to the computer
screen.
First of all, find the commit shasum of the command you want to run by taking a look into the history of the dataset (in the shared dataset):
# navigate into the shared copy
$ cd ../mock_user/DataLad-101
# lets view the history
$ git log --oneline -n 10
41ea4e6 add note on clean datasets
4753f3f [DATALAD RUNCMD] Resize logo for slides
4951771 [DATALAD RUNCMD] Resize logo for slides
926a797 add additional notes on run options
4cf3515 [DATALAD RUNCMD] convert -resize 450x450 recordings/longn...
19a9a7d resized picture by hand
91aeee9 [DATALAD RUNCMD] convert -resize 400x400 recordings/longn...
da12c3f add note on basic datalad run and datalad rerun
355446e add note datalad and git diff
d5edb18 [DATALAD RUNCMD] create a list of podcast titles
Ah, there it is, the second most recent commit. Just as already done in section DataLad, Re-Run!, take this shasum and plug it into a datalad rerun command:
$ datalad rerun 4753f3f58f6cb9b2a70f71ad56fd0173c453853f
[INFO] run commit 4753f3f; (Resize logo for s...)
[INFO] Making sure inputs are available (this may take some time)
get(ok): recordings/longnow/.datalad/feed_metadata/logo_salt.jpg (file) [from origin...]
[WARNING] no content present; cannot unlock [unlock(/home/me/dl-101/mock_user/DataLad-101/recordings/salt_logo_small.jpg)]
remove(ok): recordings/salt_logo_small.jpg
[INFO] == Command start (output follows) =====
[INFO] == Command exit (modification check follows) =====
add(ok): recordings/salt_logo_small.jpg (file)
action summary:
add (ok: 1)
get (notneeded: 1, ok: 1)
remove (ok: 1)
save (notneeded: 2)
“This was so easy!” you exclaim. DataLad retrieved the missing
file content from the subdataset and it tried to unlock the output
prior to the command execution. Note that because you did not retrieve
the output, recordings/salt_logo_small.jpg
, yet, the missing content
could not be unlocked. DataLad warns you about this, but proceeds
successfully.
Your room mate now not only knows how exactly the resized file came into existence, but he can also reproduce your exact steps to create it. “This is as reproducible as it can be!” you think in awe.