[PATCH v3 0/1] ref-filter: add new "signature" atom

This commit duplicates the code for `signature` atom from pretty.c to ref-filter.c. This feature will help to get rid of current duplicate implementation of `signature` atom when unifying implementations by using ref-filter logic everywhere when ref-filter can do everything pretty is doing.

Add "signature" atom with `grade`, `signer`, `key`, `fingerprint`, `primarykeyfingerprint`, `trustlevel` as arguments. This code and its documentation are inspired by how the %GG, %G?, %GS, %GK, %GF, %GP, and %GT pretty formats were implemented.

Co-authored-by: Hariom Verma <hariom18599@gmail.com>
Co-authored-by: Jaydeep Das <jaydeepjd.8914@gmail.com>
Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Mentored-by: Hariom Verma <hariom18599@gmail.com>
Signed-off-by: Nsengiyumva Wilberforce <nsengiyumvawilberforce@gmail.com>

Nsengiyumva Wilberforce (1):
  ref-filter: add new "signature" atom

 Documentation/git-for-each-ref.txt |  27 +++++++
 ref-filter.c                       | 101 +++++++++++++++++++++++++
 t/t6300-for-each-ref.sh            | 116 +++++++++++++++++++++++++++++
 3 files changed, 244 insertions(+)

Range-diff against v2: 1: ce51d8e79e = 1: ce51d8e79e ref-filter: add new "signature" atom