strv_make_nulstr() is documented to always return a valid nulstr,
but if the input is `NULL` we return a string terminated with only
a single NUL terminator, so let's fix that and always terminate the
resulting string with two NUL bytes.
Originally, the table formatting code was written to display a number of
records, one per line, and within each line multiple fields of the same
record. The first line contains the column names.
It was then started to be used in a "vertical" mode however,
i.e. with field names on the left instead of the top. Let's support such
a mode explicitly, so that we can provide systematic styling, and can
properly convert this mode to JSON.
A new constructor "table_new_vertical()" is added creating such
"vertical" tables. Internally, this is a table with two columns: "key"
and "value". When outputting this as JSON we'll output a single JSON
object, with key/value as fields. (Which is different from the
traditional output where we'd use the first line as JSON field names,
and output an array of objects).
A new cell type TABLE_FIELD is added for specifically marking the
"field" cells, i.e. the cells in the first column. We'll automatically
suffic ":" to these fields on output.
This is useful to force off fancy unicode glyph use (i.e. use "->"
instead of "→"), which is useful in tests where locales might be
missing, and thus control via $LC_CTYPE is not reliable.
Use this in TEST-58, to ensure the output checks we do aren't confused
by missing these glyphs being unicode or not.
Let's say we have the following repart definitions files root.conf
and home.conf:
```
[Partition]
Type=root
CopyFiles=/
```
```
[Partition]
Type=home
CopyFiles=/home
```
Currently, we'd end up copying /home to both the root partition and
the home partition. To prevent this from happening, let's adopt a
new policy when copying files for a partition: We won't copy any
files/directories that appear in the CopyFiles= list of another
partition, unless that directory explicitly appears in our own
CopyFiles= list.
This way, we prevent copying /home twice into the root and home
partition, but should a user really want that behavior, they can
have it by adding /home to the CopyFIles= list of the root partition
as well.
