$ git diff --line-prefix=abc main main^ side
abcdiff --cc dir/sub
abcindex cead32e,7289e35..992913c
abc--- a/dir/sub
abc+++ b/dir/sub
abc@@@ -1,6 -1,4 +1,8 @@@
abc  A
abc  B
abc +C
abc +D
abc +E
abc +F
abc+ 1
abc+ 2
abcdiff --cc file0
abcindex b414108,f4615da..10a8a9f
abc--- a/file0
abc+++ b/file0
abc@@@ -1,6 -1,6 +1,9 @@@
abc  1
abc  2
abc  3
abc +4
abc +5
abc +6
abc+ A
abc+ B
abc+ C
$