Luis Ballblog

How to make the last commit message your gh-pages commit message

May 19, 2021

Until recently I hadn’t bothered to look at how the gh-pages package was titling the commits. Turns out, it was just as a super unhelpful Updates. Yikes.

So over lunch I poured over the docs only to find they have an API that allows you change this. Nice! All you need to do is use the --message flag.

gh-pages -d public -b main --message $SOME_MESSAGE

Problem is I don’t want yet another unhelpful commit tittle. Instead, I’d like at least some context of what’s being changed to be passed in.

Although not perfect, the last commit message from master-source branch will have this.

Use the last commit from the current branch as the gh-pages commit message

We can add the last commit message to the --message flag by using git’s log and pretty APIs.

# outputs last commit title in one line
git log -1 --pretty=%B

If we save that to a variable, $DEPLOY_MESSAGE, we can reference it in package.json’s deploy script.

"deploy": "DEPLOY_MESSAGE=\"$(git log -1 --pretty=%B)\"; gatsby build && cp CNAME public && gh-pages -d public -b master --message $DEPLOY_MESSAGE"

The catch

This is almost perfect, except because there’s empty spaces in the commit title, the package.json script will not pass the entire commit to the --message flag for gh-pages.

So you’d end up with a commit message like this,

chore:

instead of this

chore: add deploy script variables

Lets fix it

It’s an easy fix. All we need to do is replace the empty character, ‏‏‎ ‎, in the $DEPLOY_MESSAGE variable with something else, like _.

We can do this in bash using pattern substitution.

## ${parameter/pattern/string}

DEPLOY_MESSAGE=\"$(git log -1 --pretty=%B)\";
RESULT=${DEPLOY_MESSAGE// /_};

And that’s it! Just update the deploy script with that pattern and you’re all set.

"deploy": "DEPLOY_MESSAGE=\"$(git log -1 --pretty=%B)\"; RESULT=${DEPLOY_MESSAGE// /_}; gatsby build && cp CNAME public && gh-pages -d public -b master --message $RESULT"

Now your commit messages can give you some context about what your last gh-pages push changed.