Git Tips and Tricks

The following are useful git tips and tricks.

Cleanup to a given branch

Often times a git repo needs to be brought up-to-date with the remote quickly. Using a feature branch style also means that branches need to be cleaned up as well. The following does all that.

Info

If you copy the below into git-cleanup and put it in your path, then Git will automatically consider it a subcommand. So within a git repo just run git cleanup main (note the space) will move your to the main branch, sync it with the remote, and delete any synced branches.

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#!/bin/bash

branch="$1"
if [[ -z "$1" ]]; then
    echo "No branch supplied, too dangerious to assume"
    exit 1
fi

set -u
git fetch -p
git checkout "$branch"
git pull

# shellcheck disable=SC2063 # we are looking for "*"
while IFS= read -r line; do
    git branch -d "$line" || echo "Unable to delete '$line', ignoring"
done < <(git branch | grep -v "^*" | awk '{print $1}' )
# Note: the line starting "*" is the current branch, ignore it
# try to safely delete the rest

Find the hash of the latest commit 

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# If you know you are in the HEAD commit
git rev-parse HEAD

# or, one that works regardless
git log --pretty="oneline" | head -n1 | awk '{print $1}'

Find the files that changed 

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ANCESTOR="master"
COMMMIT="HEAD" # replace with commit hash if you could be in detached head

# sync the acenstor branche to ensure it has full history
git fetch origin "$ANCESTOR:remotes/origin/$ANCESTOR"

# diff to the anscestor
git diff --name-only "origin/$ACTIVE_BRANCH"..."$COMMIT"

# Unfortunately this doesn't catch if you are on $ACTIVE_BRANCH.
# So you need to check the the last commit if the above produces no output
git diff --name-only "$COMMIT^..$COMMIT"