Initializer

When developing a Rails application (or any app) with Git, it’s sometimes useful to see which branch or commit you’re currently on. You can initialize some global constants pretty easily in Rails by creating a file under your config/initializers/ directory. I like to make a single file with all of my application-wide constants in config/initializers/global_constants.rb, but you can also split it up into specific files like config/intializers/git_info.rb for example.

Git information

To get your current branch and commit information, just stick this in your initializer file:

# Get branch information
GIT_BRANCH = `git branch`.split.last
GIT_COMMIT = `git log | sed -n 1p`

If you come across some color codes in the output, you can strip it out like so

# Strip out color codes
GIT_COMMIT = `git log | sed -n 1p`.gsub(/\x1B\[([0-9]{1,2}(;[0-9]{1,2})?)?[m|K]/,'').split.first

Tags and versions

A great feature of Git is tagging, which is typically used to tag version numbers, feature releases, and patches. An annotated tag is probably the simplest way to tag the current or any specified commit. For example:

# Simple annotated tagging
$ git tag -a v1.0.0 454ef4d -m 'Initial public release!'

Note that you can drop the 454ef4d commit specification, which would then just tag the current commit. You can also sign your tags with GPG using the -s option instead of the -a option. If you’re on GitHub, you can push your tags using git push --tags.

If you’ve been tagging along, a neat thing you can do is to display the latest version number or release in your application. Again, we can do this by creating a global constant

# Get latest tag information
APP_VERSION = `git describe --tags`.strip

which will output something similar to v1.0.0-1-g6a9ee26. The format here is [tag name]-[# commits ahead]-[current commit]. This might be useful in a development environment, but you might want to strip it down to just the version number or tag name in your production app:

# Get only tag name
APP_VERSION = `git describe --tags \`git rev-list --tags --max-count=1\`
`.strip

Now you can print the APP_VERSION or any of the other constants out in one of your views, like your site’s footer, and make your app feel super official.