GIT

GIT version management snippets.

Revert Changes and Keep Commit History

git revert --no-edit {LAST GOOD COMMIT}..{LAST BAD COMMIT}

Force Repository to Previous Commit

Should use Revert Changes and Keep Commit History.

git reset --hard {COMMIT ID}
git push --force origin master

Danger

This is data destructive. Ensure any files are cleaned up before committing.

Currently checked out versions of this repository will break.

Force Pull from Master Repository

Forces local repository to be in sync with master, discarding all local changes and unpushed commits.

git fetch --all
git reset --hard origin/master

Apply to a branch only

git checkout {BRANCH}
git fetch --all
git branch {BRANCH}-backup
git reset --hard origin/{BRANCH}

Reference

Revert Entire Directory to HEAD

git checkout -- {DIR}
git clean -fd {DIR}

Note

{DIR}/.. can be used to target all files and directories within that directory.

Add Tag to Previous Commit

git pull --tags
git tag {TAG} {COMMIT}
git push --tags

Squash Commits to a Single Commit (Rebase)

This will squash a series of commits into a single commit, which is useful to cleanup multiple commits before pushing upstream.

git rebase --interactive {COMMIT}

Note

The COMMIT is the last commit that should be collapsed (e.g. rolled into a single commit).

Editor will appear with rebase configuration. Generally use pick for the first commit and squash for the remaining commits.

git rebase --continue

Note

If done correctly, this will show all commit messages that were rolled up. Update as needed and commit as normal.

Modify Specific Historical Commit

Warning

This will re-write commit history from the changed commit; if tags, releases are used they will need to be deleted and re-created. Existing clones will break. Be careful.

Rebase to one commit before the intended change

git rebase --interactive '{COMMIT}^'

Note

Set edit for the desired commit; save and exit. Make desired changes.

Finish rebasing to HEAD

git commit --all --amend --no-edit
git rebase --continue

Reset affected tags

git tag -l
git rev-list -n 1 {TAG}
git tag -d {TAG}
git push --delete origin {TAG}
git tag {TAG} {NEW COMMIT HASH}
git push --tags

Note

Ensure affected releases, tags are removed before pushing the changed repo.

git push -f

Reference

Remove Tracked Files without Deleting Them

Single file.

git rm --cached {FILE TO REMOVE FROM COMMIT}

Multiple files.

git rm --cached {FILE1} {FILEN}

All contents of a directory.

git rm -r --cached {DIR}

Create a Branch 

Multiple branches can be made to focus changes on specific efforts. These are cut from the current branch; most cases this should be master.

List, create, and move to new branch.

git branch -a
git checkout -b {NEW BRANCH}

Use git normally.

Merging Branches

Completed branches can be merged back into any branch, typically master.

List branches, switch to master, and merge.

git branch -a
git checkout master
git merge {BRANCH} --no-ff

Note

--no-ff retains all commit messages from the branch. Leave this off to squish the commit (it may be helpful to get branch log for merge message git --no-pager log > /tmp/git.log.

You may reset the merge before committing with no data loss with get merge --abort.

Reference

Deleting Branches

Git will throw an error if deleting a branch with commits that has not been merged.

Delete merged branch.

git branch -a
git branch -d {BRANCH}

Create Worktree

Allows the use of multiple branches simultaneously.

Create a new worktree from a branch

git branch -a
git checkout -b {NEW BRANCH}
git checkout master
git worktree add ../{WORKTREE NAME} {BRANCH}

Merge Worktree

Works like normal branch merging. Execute merge from master worktree.

See Merging Branches.

Removing Worktree

After the branch is merged worktree can be removed.

Remove worktree.

cd {MASTER WORKTREE}
git worktree remove {WORKTREE}

Then delete branch as normal. See Deleting Branches.

Migrate git stash to another machine

Export a stash as a patch to import in another git client.

Export stash 0 to a patch.

git stash show "stash@{0}" -p > changes.patch

Import patch to client.

git apply changes.patch

Patch can be reverted if there are issues.

git apply changes.patch --reverse

Repo git hooks

Hooks are located in .git/hooks but are not versioned. This enables repository tracked hooks.

See .git/hooks for examples. Custom pre-commit example. Hooks must have exact names.

Create repo hooks

mkdir {REPO}/.githooks

Set local gitconfig hookspath to custom location

git config -f .gitconfig core.hooksPath .githooks

0755 user user .githooks/pre-commit

#!/usr/bin/env bash
#
# Called by "git commit" with no arguments.  The hook should
# exit with non-zero status after issuing an appropriate message if
# it wants to stop the commit. See .git/hooks for examples.

# Unset variables produce errors
set -u

if git rev-parse --verify HEAD >/dev/null 2>&1
then
	against=HEAD
else
	# Initial commit: diff against an empty tree object
	against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
fi

# Redirect output to stderr.
exec 1>&2

EXIT_STATUS=0

# Check that vault files are encrypted.
# read: -r do not allow backslashes to escape characters; -d delimiter
while IFS= read -r -d $'\0' file; do
	[[ "$file" != *.vault &&
		 "$file" != *.vault.yml &&
		 "$file" != *vault ]] && continue
	# cut gets symbols 1-2
	file_status=$(git status --porcelain -- "$file" 2>&1 | cut -c1-2)
	file_status_index=${file_status:0:1}
	file_status_worktree=${file_status:1:1}
	[[ "$file_status_worktree" != ' ' ]] && {
		echo "ERROR: *.vault file is modified in worktree but not added to the index: $file"
		echo "Can not check if it is properly encrypted. Use git add or git stash to fix this."
		EXIT_STATUS=1
	}
	# check is neither required nor possible for deleted files
	[[ "$file_status_index" = 'D' ]] && continue
	head -1 "$file" | grep --quiet '^\$ANSIBLE_VAULT;' || {
		echo "ERROR: non-encrypted *.vault file: $file"
		EXIT_STATUS=1
	}
done < <(git diff --cached --name-only -z "$against")

exit $EXIT_STATUS

Use a Makefile or manually run on repo checkout to setup.

git config --local include.path ../.gitconfig

Note

Command executes from .git directory, hence going up a directory to read the config.

List All Respositories for An Organization/User

Useful for determining if there are new repositories to sync.

List all repositories for an organzation.

curl "https://api.github.com/orgs/{ORGANIZATION NAME}/repos?per_page=1000&page=1" | jq -r '.[] | .name' | sort

List all repositories for a user.

curl "https://api.github.com/users/{USER}/repos?per_page=1000&page=1" | jq -r '.[] | .name' | sort

Pull Latest Tarball Release from Github

Useful for projects that have periodic releases but are not in OS packages.

0755 user user update_latest_tarball

#!/bin/bash
#
# Args:
#   1: github username
#   2: repository name
#   3: tarball download target (absolute path)
#   4: tarball extract target (absolute path)
RELEASE_DATA=$(curl --silent "https://api.github.com/repos/${1}/${2}/releases/latest")
TAG=$(echo ${RELEASE_DATA} | jq -r .tag_name)
URL=$(echo ${RELEASE_DATA} | jq -r '.assets[0].browser_download_url')
NAME=$(echo ${RELEASE_DATA} | jq -r '.assets[0].name')
TARBALL=${3}/${NAME}

if [ ! -f "${TARBALL}" ]; then
  curl --silent --location ${URL} --output ${TARBALL}
  tar xf ${TARBALL} --strip-components=1 -C ${4}
fi

GIT

Revert Changes and Keep Commit History

Force Repository to Previous Commit

Force Pull from Master Repository

Revert Entire Directory to HEAD

Add Tag to Previous Commit

Squash Commits to a Single Commit (Rebase)

Modify Specific Historical Commit

Remove Tracked Files without Deleting Them

Create a Branch

Merging Branches

Deleting Branches

Create Worktree

Merge Worktree

Removing Worktree

Migrate git stash to another machine

Repo git hooks

List All Respositories for An Organization/User

Pull Latest Tarball Release from Github

Create a Branch 