Git: programmatic staging

In the past year, I’ve been using a lot of tools to automatically rewrite/refactor code. These include semgrep, ast-grep, LLMs, and one-off scripts. After running these tools on a large code-base, you usually end up with lots of additional unintended changes. These range from formatting/whitespace to unrequested modifications by LLMs.

The subsequent “cleanup” step is a very manual and tedious process. I’m essentially running git add -p and staging hunks one at a time. At times it feels like this step offsets the productivity gain from the rewrite tool itself.

After doing this several times, I realized that most of the hunks I was staging included some common text. If I could automatically stage hunks containing a search term, I could automate a lot of this work! Git does not natively support this, but it can be easily accomplished using the expect tool:

#!/usr/bin/expect -f

# Set timeout to prevent the script from hanging
set timeout -1

# Get the search pattern as a command line argument
if {[llength $argv] != 0} {
   set pattern [lindex $argv 0]
} else {
   puts "Error: search pattern not provided"
   exit 1

# Open the interaction with git add -p
spawn git add -p

# This is the main loop that handles the user interaction
expect {
  # This expect block is for the hunk that contains the provided pattern
  "*$pattern*Stage this hunk*" {
    send "y\r"
  # This expect block is for continuing to the next hunk
  "*Stage this hunk*" {
    send "n\r"

To install this script, save it in your PATH with the name git-add-match. Once installed, the usage is as follows:

$ git add-match foo

After running this command, all hunks where the string “foo” is found will be staged.


A user on suggested using grepdiff instead:

git diff | grepdiff --output-matching=hunk PATTERN | git apply --cached