Have you ever found a bug-inducing line change in your code, and wondered who made the change to that line? Fortunately, git has a command for that! git blame lets you pick a file and show who last changed every line. If you were wondering, it's called git blame because it lets you assign blame for the code-breaking line you're investigating.
To find out who changed a line, simply run the following command where myfile.txt is the file you want to check:
git blame myfile.txt
If you're interested in the format of git blame, it breaks down like this:
^665221a (Johnny Simpson 2022-04-30 20:58:04 +0100 10) import { v4 as uuid } from 'uuid';
^ ^ ^
| | |
Commit ID | Line number
|
Author and timestamp
Using Git Blame on a Particular Line
This is really useful, but what if you want to hone in on a specific line, you can use the -L option. For example, if you want to see the change history between lines 1 and 5, you would do the following:
git blame index.js -L 1,5
Or, if you wanted to find the change history between lines 20 and 40, you could do the following:
git blame index.js -L 20,40
Other Useful Git Blame Options
There are also a bunch of other useful git blame options that you might want to use. Here are some of the ones I use the most, and what they do.
Showing an author's email with git blame
All you have to do to show the email address of an author only is use the -e option:
git blame index.js -e
Producing an output like this:
^665221a (<some@email.com> 2022-04-30 20:58:04 +0100 8) import { fileURLToPath } from 'url'
Ignoring whitepsace with git blame
You can also ignore whitespace with git blame, should your code contain a lot of it. To do this, you can use the -w option:
git blame index.js -w
Formatting lines with color using git blame
By default, git blame produces a wall of white or black text. If you want to differentiate different commits and changes by color, you can use the --color-lines or --color-by-age:
--color-linescolors lines if the line before was a different commit.--color-by-agecolors lines by their age.
Showing file names with git blame
To show the filename with git blame, use the -f option. This will show the file name along with the commit ID.
git blame index.js -f
Will produce an output like this:
^665221a index.js (Johnny Simpson 2022-04-30 20:58:04 +0100 16) import dotenv from 'dotenv'
Showing line changes from the bottom up (reversed) with git blame
You can also show line changes in reverse with git blame, meaning starting at the bottom, and going up. Just add the --reverse option to your command:
git blame index.js --reverse