Git extensions in Babashka

ryan-blog@rymcg.tech (EnigmaCurry) — Tue, 02 Jun 2026 00:00:00 -0600

In a previous post, I introduced git_extensions.sh – a monolithic bash script providing custom git subcommands (git vendor, git deploy, git deploy-key, git remote-proto). It worked fine. It also weighed in at 1,590 lines of bash, with global variables named things like VENDOR_SSH_PORT and URL parsing done through cascading regex in BASH_REMATCH. The kind of code where adding a feature means holding your breath and hoping set -eo pipefail catches whatever you break.

So I ported it to Babashka.

Why Babashka?

Babashka is a fast-starting Clojure scripting runtime. It ships as a single static binary, starts in under 50ms, and gives you a real language with real data structures instead of a stringly-typed minefield.

The pitch for porting a bash script to Babashka:

Maps instead of globals. URL parsing returns {:host "github.com" :path "user/repo"} instead of setting REMOTE_PROTO_HOST and praying nobody clobbers it.
Explicit parameters instead of cd. The bash version relies on cd "$dest" to set the working directory for subsequent git commands. The Babashka version passes :dir explicitly to every process call. No spooky action at a distance.
Actual testable functions. Each function takes arguments and returns values. No subshell surprises, no nameref tricks (local -n), no quoting emergencies.
63% less code. 580 lines of Clojure vs 1,590 lines of bash, with identical functionality and CLI interface.

The tradeoff is a runtime dependency – you need bb on your PATH. But if you’re already using Nix (and if you’re reading this blog, you probably are), that’s a non-issue.

What changed

Nothing, from the user’s perspective. The CLI is identical:

git vendor enigmacurry/sway-home
git deploy git@github.com:user/repo.git
git deploy-key list
git remote-proto ssh --port 2222

Same flags, same output, same symlink dispatch trick. The script detects its invoked name and dispatches accordingly, with a fallback to first-argument dispatch:

# Via symlink (git finds git-vendor in PATH):
git vendor org/repo

# Direct invocation:
bb git_extensions.bb vendor org/repo

How the port went

Most of the translation was mechanical. Bash patterns have direct Clojure equivalents:

Bash	Babashka
`[[ "$url" =~ ^git@([^:]+):(.+)$ ]]`	`(re-matches #"git@([^:]+):(.+)" url)`
`REPO_URL="${BASH_REMATCH[1]}"`	`(let [[_ host path] (re-matches ...)])`
`local -n _host=$2`	Just return a map
`check_deps git ssh-keygen`	`(check-deps "git" "ssh-keygen")`
`git remote get-url origin`	`(git-out dir "remote" "get-url" "origin")`
`awk '...' "$config_file" > "$tmp_file"`	Line processing with `loop`/`recur`

The SSH config manipulation (adding/removing Host blocks) was the most interesting part. The bash version uses awk with state tracking. The Clojure version does the same thing with a loop that tracks a skip flag – structurally identical, but without awk’s implicit line iteration.

The one genuinely tricky part was symlink detection. Babashka resolves *file* to the actual script, not the symlink. The solution tries two strategies: on Linux it reads /proc/self/cmdline (the null-separated argv), and on macOS/BSD it falls back to ps -p <pid> -o args=. Both scan the process command line for an argv entry starting with git-.

Installation

If you use my sway-home config with home-manager, it’s already wired up – the symlinks now point to git_extensions.bb.

For manual installation, you’ll need Babashka installed, then:

## Download the script and make it executable:
curl -Lo ~/.local/bin/git_extensions.bb \
  https://raw.githubusercontent.com/EnigmaCurry/blog.rymcg.tech/master/src/git/git_extensions.bb
chmod +x ~/.local/bin/git_extensions.bb

## Create symlinks for each extension:
ln -s git_extensions.bb ~/.local/bin/git-vendor
ln -s git_extensions.bb ~/.local/bin/git-deploy
ln -s git_extensions.bb ~/.local/bin/git-deploy-key
ln -s git_extensions.bb ~/.local/bin/git-remote-proto

The bash version still works and isn’t going anywhere. Use whichever you prefer.

The script

Download the script from this direct link