Running Prettier for specific Git branch

Blog/Architecture · 2020-01-14 · prettier git bash script branch file awk print echo file awk run prettier line column file mode files project

I'm working on a project in my own git branch. At the end of my working day I want to do one thing - run Prettier so my code is nicely formatted before I submit the PR for code review. Of course I know about the VSCode Prettier extension but right now my editor is kinda broken and I don't want to mess with it. I'm still on my branch and I run Prettier from the terminal. All good but the amount of changes that happened is so big that my 50+ loc updates are like a needle in a haystack. It is like that because apparently there are already malformatted files in the project. It is definitely not possible to understand what I did because of so much noise. So ... I want to run Prettier but only on the files that I touched in that particular branch.

Git to the rescue! I had to compare my branch to master, find out what are the changed files and run Prettier only for them. I decided to write a small shell script that will do this job for me. I will use it now and in the future.

#!/bin/sh

BASEDIR="<path to my project dir>"

files=$(git diff --name-status master);

while read -r file; do
  mode=$(echo "$file" | awk '{print $1}')
  filePath=$(echo "$file" | awk '{print $2}')
  if [ "$mode" = "M" ] || [ "$mode" = "A" ] || [ "$mode" = "AM" ]
    then
      npx prettier --write $filePath
  fi
done <<< "$files"

Let's go over it line by line.

files=$(git diff --name-status master); - runs git diff comparing the current branch to master. --name-status is giving us a nice two column table. The first one is what type of change we did and the second one the file path.
while read -r file; do - we loop over the table rows.
mode=$(echo "$file" | awk '{print $1}') - this line gives us the content of the first column.
filePath=$(echo "$file" | awk '{print $2}') - similarly to the line above this one gives us the value of the second column (the file path).
if [ "$mode" = "M" ] || [ "$mode" = "A" ] || [ "$mode" = "AM" ] - we check if the file is modified but not deleted. Prettier will scream if we run it against a file that doesn't exists.
npx prettier --write $filePath - at the end we format the file.

I hope it's useful. 😎