Git
Created: Miscellaneous Git Concepts
Updated: 25 March 2024
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 thedevelop
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
Find Bad Commits using Bisect
- Checkout the branch where the bad commit exists
- Run
git bisect start
to start a bisect session - Checkout a commit that is known to be bad and run
git bisect bad
- Checkout a commit that is known to be good and run
git bisect good
- Then the bisect tool will automatically checkout another commit
- Do your checks
- If good then run
git bisect good
, otherwise rungit bisect bad
- The process will run until you find the last bad commit, you can then try to figure out what was changed in that commit
- Optionally, you can checkout the HEAD of your branch, then run
git checkout <LAST_WORKING_COMMIT_HASH> .
to get the last working files in your branch and you can remove changes until you are left with some change that would be the one that caused the bug
Git User Configs
Often when using git you may need to have multiple accounts on the same machine and would like more specific control over config for different repositories - Often I would like to be able to set my email address differently for a specific repo or group of repos
To do this, you can use two solutions depending on your usecase:
Single Repository
For a repository you can update the .git/config
file for that repository using the following command:
~/repos/my-repo/.git/config
git config set user.email "repo@email.com"
For a Subdirectory
Sometimes you may have multiple subdirectories in which you would like repositories within it to inherit a specific config, you can do this by:
- Adding a conditional includes in your global git config
~/.gitconfig
file
~/.gitignore
# default value to be used outside of subdirectory
[user]
name = Nabeel Valley
email = nabeel@email.com
# link to subdirectory config
[includeIf "gitdir:~/repos/my-other-repos/"]
path = ~/repos/my-other-repos/.gitconfig
Note that for Windows you have to include the path as
C:/Users/my-user/repos/my-other-repos.
in theincludeIf
section and thepath
section
- In the subdirecroty create a
.gitconfig
file that has specifies the config for the entire subdirectory:
~/repos/my-other-repos/.gitconfig
# override value that applies to this subdirectory only
[user]
email = other@email.com
Newer Git Stuff
From Git Tips and Tricks
Log changes to specific part of file
Log changes to a specific part of a file using:
git log -L FROM,TO:path/to/file
For example:
git log -L 10,20:my/file.js
You can also do this using the name of some symbol in your code and it will try to figure that out for you:
git log -L SymbolName:path/to/file
Git Maintenance
Run the following in a repo to make git maintain the repo and keep things fast in the background using a CRON job (just run this in every repo)
git maintenance start