Git

Created: Miscellaneous Git Concepts

Updated: 29 September 2023

Stage Files Using Glob

Git allows the use of globbing to work with files, using this knowledge we’re able to do something like stage files based on a glob pattern, so we can do something like stage all .js and .ts files with:

git add **/*.{js,ts}

You can create and test glob patterns on GlobTester

Revert Commits

From StackOverflow

Revert Single Commit

Say we have a commit with id b below, and we would like undo changes that were introduced in that commit but still retain our history as is, something like:

We want to go from this state:

a -> b -> c -> d -> e

To this state:

a -> b -> c -> d -> e -> b'

Such that b' undoes the changes introduced by b, then we can use the following git command:

git revert --no-commit HEAD~4

Where HEAD~4 means the 4th last commit from the current HEAD (latest commit)

Revert Multiple Commits

Say we have a commit with id b below, and we would like undo changes that were introduced in that all changes since that commit but still retain our history as is, something like:

We want to go from this state:

a -> b -> c -> d -> e

To this state:

a -> b -> c -> d -> e -> (bcde)'

Such that (bcde)' undoes the changes introduced by all commits from b to e, then we can use the following git command:

git revert --no-commit HEAD~4..

Where HEAD~4 means the 4th last commit from the current HEAD (latest commit) and the .. means a commit range till the latest commit

Submodules

Submodules allow you to include one git repository in another, for instance if we want to include a library in our codebase

Set Up a Test Repo

We can get started on a new test repository, just create a folder with some files and other folders in it and run:

git init

Thereafter add and commit all the files in the repo:

git add .
git commit -m "initial commit"

Add a Submodule

Next, from the directory into which you want the submodule to be cloned into, you can run the following command:

git submodule add https://github.com/nabeelvalley/YourRepository.git

If we would like to change the name of the folder being cloned from the default, we can add a new name for the folder by adding it at the end of the clone command

git submodule add https://github.com/nabeelvalley/YourRepository.git NewNameForSubmoduleDirectory

This will clone the repository into a directory called NewNameForSubmoduleDirectory

You will also see a new .gitmodules file in your parent repo’s root directory created with the following:

[submodule "MySubmodules/YourRepository"]
	path = MySubmodules/YourRepository
	url = https://github.com/nabeelvalley/YourRepository.git

[submodule "MySubmodules/NewNameForSubmoduleDirectory"]
	path = MySubmodules/NewNameForSubmoduleDirectory
	url = https://github.com/nabeelvalley/YourRepository.git

You can see above an example of a submodule created with the default name as well as a renamed one

Next you will see that the new files need to be committed, you can do that with

git add .
git commit -m "add submodules"

Cloning a Project with Submodules

When cloning a project that has submodules you can do either of the following:

git clone https://github.com/nabeelvalley/MyNewRepository.git

And then updating the submodules with:

git submodule init
git submodule update

If you want to init and update all nested submodules of the repository at once you can use:

git submodule update --init

And if you want to also update any further embedded submodules you can do:

git submodule update --init --recursive

Alternatively if you are cloning the project for the first time you should be able to pull everything including the submodules with --recurse-submodules

git clone --recurse-submodules https://github.com/nabeelvalley/MyNewRepository.git

Pull Latest Changes from Submodule

To pull the latest changes from a submodule into the repository you can make use of the following command:

git submodule update --remote --merge

There’s a lot more you can do with submodules but these are the basics, more information is in the Git docs

It’s also relevant to note that when working on submodules you can kind of treat them as a normal git repository and work on them like you would if they were such

Clean Ignored Files

To remove files that are in your .gitignore but are not ignored by your repo, you can do the following:

git rm -r --cached .

Which will clean out the repo, and then you can restage and commit all the files that should be tracked with

git add .
git commit -m ".gitignore fix"

Create an Orphan/Unrelated Branch

Information from this Stack Overflow Answer

Sometimes it’s useful to start a completely fresh segment of work without carrying around previous changes, e.g. to test out a totally new application architecture

We can do this by using the following:

git checkout --orphan NEW_BRANCH_NAME
git rm -rf .

Then you can remove all old files, or do whatever work is required and then:

git add .
git commit -m 'Initial commit on new branch'

Using Git Flow

To init Git Flow in a repo use git flow for the help menu:

> git flow

usage: git flow <subcommand>

Available subcommands are:
   init      Initialize a new git repo with support for the branching model.
   feature   Manage your feature branches.
   bugfix    Manage your bugfix branches.
   release   Manage your release branches.
   hotfix    Manage your hotfix branches.
   support   Manage your support branches.
   version   Shows version information.
   config    Manage your git-flow configuration.
   log       Show log deviating from base branch.

Try 'git flow <subcommand> help' for details.

To init a new Git Flow project:

git flow init

This will then ask you to update the naming convention for your branching system, it uses the defaults as listed in the help menu above

The full log when runing the above command will look something like this:

> git flow init

Initialized empty Git repository in C:/Users/NVALLEY/source/repos/gitglow/.git/
No branches exist yet. Base branches must be created now.
Branch name for production releases: [master]
Branch name for "next release" development: [develop]

How to name your supporting branch prefixes?
Feature branches? [] feature/
Bugfix branches? [] bugfix/
Release branches? [] release/
Hotfix branches? [] hotfix/
Support branches? [] support/
Version tag prefix? []
Hooks and filters directory? [<REPO PATH/.git/hooks]

When using init you will also automatically be switched to the develop branch if you’re working on an existing project

Now you can use the git flow <BRANCH TYPE> start <FUNCTION NAME> command to start a new feature branch for something like so:

> git flow feature start save-user

Switched to a new branch 'feature/save-user'

Summary of actions:
- A new branch 'feature/save-user' was created, based on 'develop'
- You are now on branch 'feature/save-user'
Now, start committing on your feature. When done, use:
git flow feature finish save-user

The above will then add you to a feature called feature/save-user and you can then make some changes and commits on this branch

When you’re done with that you can use git flow <BRANCH TYPE> finish <FUNCTION NAME> to merge the work to develop

>  git flow feature finish save-user

Switched to branch 'develop'
Updating 012cac2..ecfd049
Fast-forward
 stuff.txt | Bin 0 -> 28 bytes
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 stuff.txt
Deleted branch feature/save-user (was ecfd049).

Summary of actions:
- The feature branch 'feature/save-user' was merged into 'develop'

You can then continue to use the above methodology to manage branching, releases, etc.

Using Git from Another Tool

Sometimes it’s useful to use git from another tool/application. To get a more standard/parseable output from git commands you can add the --porcelain flag. For example, with git status below:

> git status --porcelain

 M Random/git.md
?? Random/wsl.json
?? Random/wsl.md

As opposed to:

> git status

On branch master
Your branch is up to date with 'origin/master'.

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
        modified:   git.md

Untracked files:
  (use "git add <file>..." to include in what will be committed)
        wsl.json
        wsl.md

Consistent Line Endings

You can setup consistent line endings for repositories that are shared between Windows and *nix systems by adding the following to a .gitattributes file

.gitattributes

* text=auto eol=lf
*.{cmd,[cC][mM][dD]} text eol=crlf
*.{bat,[bB][aA][tT]} text eol=crlf

Locate your SSH Key on Windows

When using git with SSH you may have difficulties finding the location for the SSH keys to use, to find the SSH Key you need to navigate to %HOMEDRIVE%%HOMEPATH%\.ssh\ To figure out where this folder is you can do the following: start > run > %HOMEDRIVE%%HOMEPATH%. The SSH Keys being used should be located in here

Delete All Branches other than Master

Using grep and xargs you can do this using:

git branch | grep -v "master" | xargs git branch -D

Get File From Specific Branch or Commit

From this StackOverflow answer

To basically copy a version of a file from one branch or commit to another you can use git checkout with either providing the branch name or commit from which you want to get the file

git checkout branch_or_commit_sha path/to/file

So to get a specific file from a develop branch

git checkout develop src/my-file.ts

Or from a specific commit

git checkout 211512 src/my-file.ts

Checkout Previous Branch

When switching branches, we can easily go to the last branch we were on using:

git checkout -

Get Commit Changes from another Branch (Cherry Picking)

Cherry picking allows us to get a specific commit from one branch and bring it into our current branch

git cherry-pick commit_sha

For example, if we want to take the changes from commit 211512 into our branch you can use

git cherry-pick 211512

Automatically Set Upstream

When using git it can be annoying when pushing a new branch since it will always request that you setup the upstream/origin. You can configure git to do this automatically using the following command:

git config --global push.autoSetupRemote true

Enable Case Sensitivity

To ensure that git is case sensitive on non-case-sensitive systems (Windows) you can use the following command:

git config core.ignorecase false