diff: index-line: respect --abbrev in object's name

2020-08-21T19:43:05Z

A handful of Git's commands respect `--abbrev' for customizing length of abbreviation of object names. For diff-family, Git supports 2 different options for 2 different purposes, `--full-index' for showing diff-patch object's name in full, and `--abbrev' to customize the length of object names in diff-raw and diff-tree header lines, without any options to customise the length of object names in diff-patch format. When working with diff-patch format, we only have two options, either full index, or default abbrev length. Although, that behaviour is documented, it doesn't stop users from trying to use `--abbrev' with the hope of customising diff-patch's objects' name's abbreviation. Let's allow the blob object names shown on the "index" line to be abbreviated to arbitrary length given via the "--abbrev" option. To preserve backward compatibility with old script that specify both `--full-index' and `--abbrev', always show full object id if `--full-index' is specified. Signed-off-by: Đoàn Trần Công Danh Signed-off-by: Junio C Hamano

git/t/t4013/diff.diff-tree_--root_-p_--full-index_initial, branch jch

diff: index-line: respect --abbrev in object's name