When constructing views, metadata is available about the location of the
file in the view's reference branch. Allows incorporating parts of the
directory hierarchy in a view.
For example `git annex view tag=* podcasts/=*` makes a view in the form
tag/showname.
Performance impact: I benchmarked git annex view tag=* in the conference
proceedings repo to take 6.459s before this change, and 6.544s after.
FWIW, I considered making the syntax for this be podcasts/*, which might
be easier for the user to learn. However, I think it's not as good:
* The user has to then juggle two different syntaxes, and podcasts/* will
be expanded by the shell so they also need to quote it, while podcasts/=*
is unlikely to be expanded by the shell.
* It would allow for things like podcasts/*/* and *.mp3 which do not
map well into views.
This commit was sponsored by Aurélien Pinceaux.
While writing this documentation, I realized that there needed to be a way
to stay in a view like tag=* while adding a filter like tag=work that
applies to the same field.
So, there are really two ways a view can be refined. It can have a new
"field=explicitvalue" filter added to it, which does not change the
"shape" of the view, but narrows the files it shows.
Or, it can have a new view added, which adds another level of
subdirectories.
So, added a vfilter command, which takes explicit values to add to the
filter, and rejects changes that would change the shape of the view.
And, made vadd only accept changes that change the shape of the view.
And, changed the View data type slightly; now components that can match
multiple metadata values can be visible, or not visible.
This commit was sponsored by Stelian Iancu.
