Possible if the working tree has been copied from another machine or is
bind-mounted from a chroot.

Not supported by clang.

Travis limits the latter, making searching for tags fail.

That format sucks and never had any real use, got dropped from termrec ten
years ago -- save for this leftover bit.

Some files in the wild use it.

Can't use a proper JSON library, as v1 format would otherwise require
reading the whole file.  The original asciicast producer (asciinema)
outputs all required bits before the actual data starts, thus this hack
allows streaming.  Hopefully no other producer of v1 format will reorder
the fields.

Recognized fields:
* version (1, 2)
* width
* height
* timestamp

anything else is silently ignored; as we lack a full JSON parser, fancy
data structures may cause failure.

Wishlist: take "comment" or "title" as OSC title?

It reduces clarity by making code less readable.  There's a reason we write
a sum of products a*b+c*d not (a*b)+(c*d); bitwise products being similar.