In a custom pretty format, using the '+' or ' ' combinators to prefix
a non-empty expansion with whitespace will erroneously truncate
subsequent expansions of the same type.
Normally '%+X' inserts a newline before <X>, IFF the expansion of X is
non-empty:
$ git log -n 1 --pretty='format:newline:%+an'
newline:
MyName
For the abbreviated commit hash placeholder ('h'), pretty.c uses
add_again() to cache the result of the expansion, and then uses that
result in future expansions. This causes problems when the expansion
includes whitespace:
$ git log -n 1 --pretty='format:newline:%+h%nno_newline:%h'
newline:
a0b1c2d
no_newline:
a0b1c2
The second expansion of the hash added an unwanted newline and removed
the final character. It seemingly used the cached expansion *starting
from the inserted newline*.
The expected output is:
$ git log -n 1 --pretty='format:newline:%+h%nno_newline:%h'
newline:
a0b1c2d
no_newline:a0b1c2d
/CC René from commit b9c62321 and Junio from 9fa708d