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content/blog/ahead-behind-git.md

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+---
+title: "Figuring out which git repositories are ahead or behind"
+date: 2023-11-09T21:05:34-05:00
+draft: false
+tags: []
+math: false
+medium_enabled: false
+---
+
+More often than I care to admit, I would pick up to do work on a device only to realize that I'm working with an older version of the codebase. I could use the `git status` command, but the output is verbose and stale if you haven't `git fetch/pull`'d.
+
+I keep the majority of my git repositories in the folder `~/repo/` on all my devices. Inspired by a recent [blog post by Clayton Errington](https://claytonerrington.com/blog/git-status/), I wanted a way to quickly check within a folder which repositories need updating.  Their blog post has a script written in PowerShell. I decided to write my own bash implementation, and also ignore the bit about modified files since I mostly care about the state of my commits with respect to the `origin` remote.
+
+Before writing a recursive implementation, let's first discuss how to check the ahead/behind status for a single repository.
+
+First things first, you need to make sure that we have all the references from the remote.
+
+```bash
+git remote update
+```
+
+To print out how many commits the local `main` branch is ahead of the one located on the `origin` remote we can use:
+
+```bash
+git rev-list --count origin/main..main
+```
+
+Similarly for checking how many commits the local `main` branch is behind we can use:
+
+```bash
+git rev-list --count main..origin/main
+```
+
+Instead of looking at the `main` branch, maybe we can to check whichever branch we're currently at.
+
+```bash
+branch=$(git rev-parse --abbrev-ref HEAD)
+```
+
+We can wrap all of this into a nice bash function. We'll additionally check if there is a `.git` in the current folder as none of the git commands will work without it.
+
+```bash
+check_remote() {
+  if [ -d .git ]; then
+    git remote update > /dev/null 2> /dev/null
+    branch=$(git rev-parse --abbrev-ref HEAD)
+    ahead=$(git rev-list --count origin/$branch..$branch)
+    behind=$(git rev-list --count $branch..origin/$branch)
+    echo "$ahead commits ahead, $behind commits behind"
+  fi
+}
+```
+
+I currently have 15 repositories in my `~/repo` folder. Now I can `cd` into each of them and run this bash function. Or, I can have `bash` do it for me :)
+
+Let's write a function called `process` that does just that. We'll pass in a folder as an argument stored in `$1`
+
+```bash
+process() {
+  if [ -d "$1/.git" ]; then
+    pushd "$PWD" > /dev/null
+    cd "$1"
+    echo -n "$1 "
+    check_remote
+    popd > /dev/null
+  fi
+}
+```
+
+The `pushd` command will keep track of the folder that we're currently in. Then we `cd` into the directory that has `.git` folder. Print the name of the folder so we can associate the ahead/behind counts, and then run the `check_remote` function. Lastly we `popd` back to the folder we started from.
+
+All that's left is to get the list of folders to process:
+
+```bash
+find . -type d -print0
+```
+
+Feed it into a `while read` loop passing in each folder into the `process` function.
+
+```bash
+find . -type d -print0 | while read -d $'\0' folder
+do
+  process $folder
+done
+```
+
+All together the script will look like:
+
+```bash
+#!/bin/bash
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+show_usage() {
+  echo "Usage: git-remote-status [-R]"
+  exit 1
+}
+
+check_remote() {
+  if [ -d .git ]; then
+    git remote update > /dev/null 2> /dev/null
+    branch=$(git rev-parse --abbrev-ref HEAD)
+    ahead=$(git rev-list --count origin/$branch..$branch)
+    behind=$(git rev-list --count $branch..origin/$branch)
+    echo "$ahead commits ahead, $behind commits behind"
+  fi
+}
+
+if [ "$#" -eq 0 ]; then
+  check_remote
+  exit 0
+fi
+
+if [ "$1" != "-R" ]; then 
+  show_usage
+  exit 1
+fi
+
+
+process() {
+  if [ -d "$1/.git" ]; then
+    pushd "$PWD" > /dev/null
+    cd "$1"
+    echo -n "$1 "
+    check_remote
+    popd > /dev/null
+  fi
+}
+export -f process
+
+find . -type d -print0 | while read -d $'\0' folder
+do
+  process $folder
+done
+```
+
+This gives us two options. If we pass in no flags, then it'll print out the ahead/behind status for the current folder. If we pass in `-R`, then we recursively check all the subfolders as well.
+
+Example Output of `git-remote-status -R`:
+
+```
+./project1 0 commits ahead, 3 commits behind
+./project2 1 commits ahead, 0 commits behind
+./project3 1 commits ahead, 2 commits behind
+./project4 0 commits ahead, 0 commits behind
+./project5 0 commits ahead, 0 commits behind
+
+```
+