[GSoC PATCH v2 0/2] diff: improve scaling of filenames in diffstat to handle UTF-8 chars

Added a test (as Junio Hamano suggested) to check how the generated diffstat handles UTF-8 characters when given various `name-width`s.

This allowed me to notice a bug where, if the given `name-width` was 2 or less, the `len` variable would become negative, entering an infinite loop. So I also fixed this bug.

LorenzoPegorari (2):
  diff: improve scaling of filenames in diffstat to handle UTF-8 chars
  t4073: add test for diffstat paths length when containing UTF-8 chars

 diff.c                          | 17 ++++-----
 t/meson.build                   |  1 +
 t/t4073-diff-stat-name-width.sh | 61 +++++++++++++++++++++++++++++++++
 3 files changed, 68 insertions(+), 11 deletions(-)
 create mode 100755 t/t4073-diff-stat-name-width.sh

Range-diff against v1:
1:  63e73122d1 ! 1:  abeb8d3439 diff: improve scaling of filenames in diffstat to handle UTF-8 chars
    @@ Commit message
         characters to drop from the filename, rather than their display width, using
         the `utf8_width()` function.
     
    +    Force `len` to not be less than 0 (this happens if the given `name-width` is
    +    2 or less), otherwise an infinite loop is entered.
    +
         Signed-off-by: LorenzoPegorari <lorenzo.pegorari2002@gmail.com>
     
      ## diff.c ##
    @@ diff.c: static void show_stats(struct diffstat_t *data, struct diff_options *opt
     -			 * leave the resulting string still too long.
     -			 */
     -			name += name_len - len;
    ++			if (len < 0)
    ++				len = 0;
     +
     +			while (name_len > len)
     +				name_len -= utf8_width((const char**)&name, NULL);
-:  ---------- > 2:  ee088ea6ef t4073: add test for diffstat paths length when containing UTF-8 chars