Bug#841499: support searching in multiple directories for matching files

[Osamu Aoki]

severity 819170 wishlist
forcemerge 819170 827814 841499
thanks

  https://bugs.debian.org/819170
  https://bugs.debian.org/827814
  https://bugs.debian.org/841499

Thanks for reminding this fundamental problem of uscan.
These are all the same problem.

Current uscan watch line parser is not written to parse more than 1 line
to pick up the best available version.

This requires process_watchline functions to be split in 2 phases.
 * process_watchline()
   - Get the list of candidates for a watch line
     (no selection of download version or source)
 * select_download()
   - Select the best download over multiple of watch lines

Then process_watchfile() can be rewritten to loop over multiple lines
with rocess_watchline() and pass the candidates to the
select_download().

In order to this to be realized, serious refactoring and code
normalization is needed.  Once that is done and with the use of extra
opts=... for each watch line, this is possible.

If done correctly, added benefit will be FTP site with version embedded
path.  Now we select fixed version of latest path first.  But we may
delay it to ensure actual matched file fixed-filename.tar.gz exists
first in the following example.

ftp://example.org/download/([^/]*)//([^/]*)/ fixed-filename.tar.gz \
   debian uudate

If upstream makes empty directory, current uscan is trickled to pick
empty directory and fail to download the available latest version.

Regards,

Osamu