A collection of git tips

Fri 19 February 2016 by Lars Kellogg-Stedman Tags git

This is a small collection of simple git tips and tricks I use to make my life easier.

Quickly amend an existing commit with new files

I have this alias in place that will amend the current commit while automatically re-using the existing commit message:

alias.fix=commit --amend -C HEAD

With this in place, fixing a review becomes:

$ vim some/file/somewhere
$ git add -u
$ git fix

Which I find much more convenient than git commit --amend, following by saving the commit message.

What files have changed?

Sometimes, I just want to know what files were changed in a commit. I have the following alias, because I have a hard time remembering whether I want --name-only or --names-only or --only-names...

alias.changed=show --name-only

Which gets me the commit message and a list of changed files:

$ git changed
commit 8c2a00809817a047bf312b72f390b5cb50ef9819
Author: Lars Kellogg-Stedman <lars@redhat.com>
Date:   Wed Feb 17 11:11:02 2016 -0500

    yet another attempt at fixing image fetching

    this uses curl rather than wget, because wget chokes on file:// urls
    which makes it difficult to cache images locally.  curl supports
    resuming downloads, but explicitly rather than implicitly like wget,
    so we need a do/until loop.

    Change-Id: Ibd3c524ea6ddfd423aec439f9eb7fffa62dfe818

:100644 100644 342a002... 2b9f9cb... M  playbooks/roles/libvirt/setup/undercloud/tasks/main.yml
:100644 000000 d22cb99... 0000000... D  playbooks/roles/libvirt/setup/undercloud/templates/get-undercloud.sh.j2

Getting the name of the current branch

For scripting purposes I often want the name of the current branch. Rather than reading git rev-parse --help every time, I have this alias:

alias.branch-name=rev-parse --abbrev-ref --symbolic-full-name HEAD

Which gets me:

$ git branch-name
master
$ git checkout bug/missing-become
$ git branch-name
bug/missing-become

Prevent accidental commits on master

When working on upstream projects I always want to be working on a feature branch. To prevent accidental commits on master I drop the following script into .git/hooks/pre-commit:

#!/bin/sh

current_branch=$(git branch-name)

if [ "$current_branch" = "master" ]; then
  echo "*** DO NOT COMMIT ON MASTER"
  exit 1
fi

exit 0

If I try to commit to my local master branch, I get:

$ git ci -m 'made a nifty change'
*** DO NOT COMMIT ON MASTER

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