man -Tlint feh

  STYLE: no blank before trailing delimiter: Em Note:
  WARNING: skipping paragraph macro: Pp after Sh

  no blank before trailing delimiter
    (mdoc) The last argument of a macro that supports trailing
    delimiter arguments is longer than one byte and ends with a
    trailing delimiter. Consider inserting a blank such that the
    delimiter becomes a separate argument, thus moving it out of
    the scope of the macro.

  skipping paragraph macro
    In mdoc(7) documents, this happens

      - at the beginning and end of sections and subsections
      - right before non-compact lists and displays
      - at the end of items in non-column, non-compact lists
      - and for multiple consecutive paragraph macros.

    In man(7) documents, it happens

      - for empty P, PP, and LP macros
      - for IP macros having neither head nor body arguments
      - for br or sp right after SH or SS

  https://man.openbsd.org/mandoc.1

  man: feh.1:1483:9: STYLE: no blank before trailing delimiter: Em Note:
  man: feh.1:1897:2: WARNING: skipping paragraph macro: Pp after Sh

There are two warnings here.

  1. This is fixed by adding a zero-width space (\&) so that the
     trailing delimiter character (:) is no longer at the end.
     This also adds this to a few other similar examples. The man page
     should render the same after this change.

  2. Removed an extra .Pp macro as suggested by the warning, this does
     not change how the man page renders.

This fixes the following mandoc warnings.

  man -Tlint feh

  WARNING: skipping empty macro: No

  skipping empty macro
    (mdoc) The indicated macro has no arguments and hence no effect.

  man: /tmp/man1/feh.1:16:14: WARNING: skipping empty macro: No
  man: /tmp/man1/feh.1:16:34: WARNING: skipping empty macro: No
  man: /tmp/man1/feh.1:179:2: WARNING: skipping empty macro: No
  man: /tmp/man1/feh.1:387:48: WARNING: skipping empty macro: No
  man: /tmp/man1/feh.1:785:26: WARNING: skipping empty macro: No
  man: /tmp/man1/feh.1:785:38: WARNING: skipping empty macro: No
  man: /tmp/man1/feh.1:823:26: WARNING: skipping empty macro: No

This fixes many warnings shown by mandoc lint feature and should also respect
the 80 col limit.

  man -Tlint feh

  WARNING: new sentence, new line

  new sentence, new line
    (mdoc) A new sentence starts in the middle of a text line. Start it on a new
    input line to help formatters produce correct spacing.

man: /usr/man/man1/feh.1.gz:35:32: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:78:33: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:90:50: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:95:53: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:97:23: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:108:17: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:112:36: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:115:24: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:122:20: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:129:21: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:130:9: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:135:19: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:146:64: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:148:43: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:149:58: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:167:2: WARNING: skipping empty macro: No
man: /usr/man/man1/feh.1.gz:175:21: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:177:30: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:178:19: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:186:42: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:189:15: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:199:49: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:213:6: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:227:47: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:231:19: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:242:11: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:274:66: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:285:19: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:297:9: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:311:19: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:340:21: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:351:14: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:360:69: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:365:44: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:372:35: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:395:21: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:396:16: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:397:31: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:406:65: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:407:53: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:430:11: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:440:24: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:442:11: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:447:24: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:455:10: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:458:22: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:491:23: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:492:44: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:493:42: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:498:26: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:511:59: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:512:55: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:530:18: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:531:46: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:532:24: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:533:41: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:538:50: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:545:13: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:562:11: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:569:41: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:576:26: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:584:23: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:607:49: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:616:61: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:617:76: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:623:61: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:635:23: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:638:27: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:640:37: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:650:17: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:666:37: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:677:42: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:682:20: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:683:8: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:688:24: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:703:51: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:714:37: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:728:23: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:729:44: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:738:61: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:775:34: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:778:42: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:787:36: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:822:19: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:823:22: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:852:46: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:868:26: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:881:10: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:889:10: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:902:43: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:920:65: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:934:23: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:954:69: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:965:37: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:973:65: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:987:17: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1027:29: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1056:17: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1143:28: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1164:38: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1171:49: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1240:54: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1271:58: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1289:22: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1291:57: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1292:59: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1293:53: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1318:32: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1329:35: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1335:13: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1341:18: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1349:22: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1358:24: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1391:44: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1398:25: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1399:8: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1405:67: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1408:23: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1569:22: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1680:21: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1681:70: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1683:22: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1708:55: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1723:36: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1742:54: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1743:45: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1771:67: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1816:35: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1822:14: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1845:47: WARNING: new sentence, new line
man: /usr/man/man1/feh.1.gz:1902:56: WARNING: new sentence, new line

Closes #386

Closes #272

Closes #218

FWIW: This behaviour was already present before
394517d1

Closes #326

closes #302

closes #270

Many image collections are organized by directory, so it is nice to have
jump-to-adjacent-directory navigation.

e.g. Given the following file hierarchy:

    .
    ├── A
    │   ├── 1.jpg
    │   ├── 2.jpg
    │   └── C
    │       ├── 1.jpg
    │       ├── 2.jpg
    │       └── 3.jpg
    └── B
        ├── 1.jpg
        ├── 2.jpg
        └── 3.jpg

`feh --recursive` creates the following filelist:

    A/1.jpg <---- current_file
    A/2.jpg
    A/C/1.jpg
    A/C/2.jpg
    A/C/3.jpg
    B/1.jpg
    B/2.jpg
    B/3.jpg

If we press [next_dir], we move the current_file pointer to:

    A/1.jpg
    A/2.jpg
    A/C/1.jpg <-- current_file
    A/C/2.jpg
    A/C/3.jpg
    B/1.jpg
    B/2.jpg
    B/3.jpg

Pressing [next_dir] again moves the pointer to:

    A/1.jpg
    A/2.jpg
    A/C/1.jpg
    A/C/2.jpg
    A/C/3.jpg
    B/1.jpg <---- current_file
    B/2.jpg
    B/3.jpg

[next_dir] now moves the pointer back to the top of the list:

    A/1.jpg <---- current_file
    A/2.jpg
    A/C/1.jpg
    A/C/2.jpg
    A/C/3.jpg
    B/1.jpg
    B/2.jpg
    B/3.jpg

Pressing [prev_dir] from here moves backwards to the first image of the
previous directory:

    A/1.jpg
    A/2.jpg
    A/C/1.jpg
    A/C/2.jpg
    A/C/3.jpg
    B/1.jpg <---- current_file
    B/2.jpg
    B/3.jpg

When starting from an position that is not the first image of a
directory, [prev_dir] moves the pointer to the first image of the
current directory.

These actions combine well with `--sort dirname` since all regular files
in a directory will be sorted before any subdirectories, avoiding a
filelist like the following:

    A/1.jpg
    A/SUBDIR/2.jpg
    A/SUBDIR/3.jpg
    A/4.jpg

With `--sort dirname` that filelist becomes:

    A/1.jpg
    A/4.jpg
    A/SUBDIR/2.jpg
    A/SUBDIR/3.jpg