Git command to programatically add a range of lines of a file to the index?

Question

I want a command that would let me do something like:

git manual-add some_file.txt 10..20

Which would be the equivalent of:

git add -p some_file.txt

and saying y to only the hunk containing lines 10 through 20.

Is there an internal git command that would let me do this? Is there any way it could be done?

Answer 1

You can take advantage of the git add -e command and pass to it as an editor a script (in the example below, it is named filterpatch) that will edit the patch up to your requirements (see the "EDITING PATCHES" section in the documentation of git add):

EDITOR="filterpatch 10..20" git add -e some_file.txt

For convenience you can add a git alias as follows:

git config alias.manual-add '!EDITOR="filterpatch $2" git add -e $1; :'

An example of a silly filterpatch script that prepends a foo prefix to all added lines in the specified range of the patch:

#!/bin/bash -x

sed -i "$1 s/^+\([^+]\)/+foo \1/" "$2"

Usage example:

git manual-add some_file.txt 13,16

So the remaining part is about implementing the filterpatch script properly - it must parse the diff and unselect hunks that don't belong to the target range.

Answer 2

Add alias to your config:

[alias]
        addp = "!sh -c 'git commit -m temp \"$1\" && git log -1 -u -L \"$2\":\"$1\" > ptc.patch && git reset HEAD^ && git apply --cached ptc.patch ' -"

Now you could:

git addp a.txt 3,4

This sequence will:

1. Do a temporary commit with file $1 only.
2. Write patch ptc.patch for lines $2 in file $1 using solution from this question - Git: discover which commits ever touched a range of lines.
3. Mixed reset temporary commit.
4. Apply patch to index only, since working directory already contains changes.