In git, is there any (simple) way to modify the index so that only changes to files which are already in it are added? It sounds kind of complicated, but what I want to achieve is simple.
Lets say my index looks like this (slightly stripped git status output):
# Changes to be committed:
# modified: A
# modified: B
#
# Changed but not updated:
# modified: B
# modified: C
#
# Untracked files:
# D
Some changes to B are in the index, some aren't.
C is not staged at all.
How can I update B in the index (stage its unstaged changes) without adding C?
I.e. I would like for the index to look like this:
# Changes to be committed:
# modified: A
# modified: B
#
# Changed but not updated:
# modified: C
#
# Untracked files:
# D
In this simple case it can of course be achieved with a simple git add B, but I would like to know if there's a simple answer for the general case. I tried git add --refresh, but if I understand correctly, that only updates stat info.
Answer
The following command will update the index to contain the other changes in B that has not been staged yet:
git update-index --again