Throughout the book we have introduced dozens of Git commands and have tried hard to introduce them within something of a narrative, adding more commands to the story slowly. However, this leaves us with examples of usage of the commands somewhat scattered throughout the whole book.
In this appendix, we’ll go through all the Git commands we addressed throughout the book, grouped roughly by what they’re used for. We’ll talk about what each command very generally does and then point out where in the book you can find us having used it.
There are two commands that are used quite a lot, from the first invocations of Git to common every day tweaking and referencing, the config and help commands.
Git has a default way of doing hundreds of things. For a lot of these things, you can tell Git to default to doing them a different way, or set your preferences. This involves everything from telling Git what your name is to specific terminal color preferences or what editor you use. There are several files this command will read from and write to so you can set values globally or down to specific repositories.
The git config command has been used in nearly every chapter of the book.
In [_first_time] we used it to specify our name, email address and editor preference before we even got started using Git.
In [_git_aliases] we showed how you could use it to create shorthand commands that expand to long option sequences so you don’t have to type them every time.
In [_rebasing] we used it to make --rebase the default when you run git pull.
In [_credential_caching] we used it to set up a default store for your HTTP passwords.
In [_keyword_expansion] we showed how to set up smudge and clean filters on content coming in and out of Git.
Finally, basically the entirety of [_git_config] is dedicated to the command.
The git help command is used to show you all the documentation shipped with Git about any command. While we’re giving a rough overview of most of the more popular ones in this appendix, for a full listing of all of the possible options and flags for every command, you can always run git help <command>.
We introduced the git help command in [_git_help] and showed you how to use it to find more information about the git shell in [_setting_up_server].
There are two ways to get a Git repository. One is to copy it from an existing repository on the network or elsewhere and the other is to create a new one in an existing directory.
To take a directory and turn it into a new Git repository so you can start version controlling it, you can simply run git init.
We first introduce this in [_getting_a_repo], where we show creating a brand new repository to start working with.
We talk briefly about how you can change the default branch from ``master'' in [_remote_branches].
We use this command to create an empty bare repository for a server in [_bare_repo].
Finally, we go through some of the details of what it actually does behind the scenes in [_plumbing_porcelain].
The git clone command is actually something of a wrapper around several other commands. It creates a new directory, goes into it and runs git init to make it an empty Git repository, adds a remote (git remote add) to the URL that you pass it (by default named origin), runs a git fetch from that remote repository and then checks out the latest commit into your working directory with git checkout.
The git clone command is used in dozens of places throughout the book, but we’ll just list a few interesting places.
It’s basically introduced and explained in [_git_cloning], where we go through a few examples.
In [_git_on_the_server] we look at using the --bare option to create a copy of a Git repository with no working directory.
In [_bundling] we use it to unbundle a bundled Git repository.
Finally, in [_cloning_submodules] we learn the --recursive option to make cloning a repository with submodules a little simpler.
Though it’s used in many other places through the book, these are the ones that are somewhat unique or where it is used in ways that are a little different.
For the basic workflow of staging content and committing it to your history, there are only a few basic commands.
The git add command adds content from the working directory into the staging area (or `index'') for the next commit. When the `git commit command is run, by default it only looks at this staging area, so git add is used to craft what exactly you would like your next commit snapshot to look like.
This command is an incredibly important command in Git and is mentioned or used dozens of times in this book. We’ll quickly cover some of the unique uses that can be found.
We first introduce and explain git add in detail in [_tracking_files].
We mention how to use it to resolve merge conflicts in [_basic_merge_conflicts].
We go over using it to interactively stage only specific parts of a modified file in [_interactive_staging].
Finally, we emulate it at a low level in [_tree_objects], so you can get an idea of what it’s doing behind the scenes.
The git status command will show you the different states of files in your working directory and staging area. Which files are modified and unstaged and which are staged but not yet committed. In it’s normal form, it also will show you some basic hints on how to move files between these stages.
We first cover status in [_checking_status], both in it’s basic and simplified forms. While we use it throughout the book, pretty much everything you can do with the git status command is covered there.
The git diff command is used when you want to see differences between any two trees. This could be the difference between your working environment and your staging area (git diff by itself), between your staging area and your last commit (git diff --staged), or between two commits (git diff master branchB).
We first look at the basic uses of git diff in [_git_diff_staged], where we show how to see what changes are staged and which are not yet staged.
We use it to look for possible whitespace issues before committing with the --check option in [_commit_guidelines].
We see how to check the differences between branches more effectively with the git diff A…B syntax in [_what_is_introduced].
We use it to filter out whitespace differences with -b and how to compare different stages of conflicted files with --theirs, --ours and --base in [_advanced_merging].
Finally, we use it to effectively compare submodule changes with --submodule in [_starting_submodules].
The git difftool command simply launches an external tool to show you the difference between two trees in case you want to use something other than the built in git diff command.
We only briefly mention this in [_git_diff_staged].
The git commit command takes all the file contents that have been staged with git add and records a new permanent snapshot in the database and then moves the branch pointer on the current branch up to it.
We first cover the basics of committing in [_committing_changes]. There we also demonstrate how to use the -a flag to skip the git add step in daily workflows and how to use the -m flag to pass a commit message in on the command line instead of firing up an editor.
In [_undoing] we cover using the --amend option to redo the most recent commit.
In [_git_branches_overview], we go into much more detail about what git commit does and why it does it like that.
We looked at how to sign commits cryptographically with the -S flag in [_signing_commits].
Finally, we take a look at what the git commit command does in the background and how it’s actually implemented in [_git_commit_objects].
The git reset command is primarily used to undo things, as you can possibly tell by the verb. It moves around the HEAD pointer and optionally changes the index or staging area and can also optionally change the working directory if you use --hard. This final option makes it possible for this command to lose your work if used incorrectly, so make sure you understand it before using it.
We first effectively cover the simplest use of git reset in [_unstaging], where we use it to unstage a file we had run git add on.
We then cover it in quite some detail in [_git_reset], which is entirely devoted to explaining this command.
We use git reset --hard to abort a merge in [_abort_merge], where we also use git merge --abort, which is a bit of a wrapper for the git reset command.
The git rm command is used to remove files from the staging area and working directory for Git. It is similar to git add in that it stages a removal of a file for the next commit.
We cover the git rm command in some detail in [_removing_files], including recursively removing files and only removing files from the staging area but leaving them in the working directory with --cached.
The only other differing use of git rm in the book is in [_removing_objects] where we briefly use and explain the --ignore-unmatch when running git filter-branch, which simply makes it not error out when the file we are trying to remove doesn’t exist. This can be useful for scripting purposes.
The git mv command is a thin convenience command to move a file and then run git add on the new file and git rm on the old file.
We only briefly mention this command in [_git_mv].
The git clean command is used to remove unwanted files from your working directory. This could include removing temporary build artifacts or merge conflict files.
We cover many of the options and scenarios in which you might used the clean command in [_git_clean].
There are just a handful of commands that implement most of the branching and merging functionality in Git.
The git branch command is actually something of a branch management tool. It can list the branches you have, create a new branch, delete branches and rename branches.
Most of [_git_branching] is dedicated to the branch command and it’s used throughout the entire chapter. We first introduce it in [_create_new_branch] and we go through most of it’s other features (listing and deleting) in [_branch_management].
In [_tracking_branches] we use the git branch -u option to set up a tracking branch.
Finally, we go through some of what it does in the background in [_git_refs].
The git checkout command is used to switch branches and check content out into your working directory.
We first encounter the command in [_switching_branches] along with the git branch command.
We see how to use it to start tracking branches with the --track flag in [_tracking_branches].
We use it to reintroduce file conflicts with --conflict=diff3 in [_checking_out_conflicts].
We go into closer detail on it’s relationship with git reset in [_git_reset].
Finally, we go into some implementation detail in [_the_head].
The git merge tool is used to merge one or more branches into the branch you have checked out. It will then advance the current branch to the result of the merge.
The git merge command was first introduced in [_basic_branching]. Though it is used in various places in the book, there are very few variations of the merge command — generally just git merge <branch> with the name of the single branch you want to merge in.
We covered how to do a squashed merge (where Git merges the work but pretends like it’s just a new commit without recording the history of the branch you’re merging in) at the very end of [_public_project].
We went over a lot about the merge process and command, including the -Xignore-space-change command and the --abort flag to abort a problem merge in [_advanced_merging].
We learned how to verify signatures before merging if your project is using GPG signing in [_signing_commits].
Finally, we learned about Subtree merging in [_subtree_merge].
The git mergetool command simply launches an external merge helper in case you have issues with a merge in Git.
We mention it quickly in [_basic_merge_conflicts] and go into detail on how to implement your own external merge tool in [_external_merge_tools].
The git log command is used to show the reachable recorded history of a project from the most recent commit snapshot backwards. By default it will only show the history of the branch you’re currently on, but can be given different or even multiple heads or branches from which to traverse. It is also often used to show differences between two or more branches at the commit level.
This command is used in nearly every chapter of the book to demonstrate the history of a project.
We introduce the command and cover it in some depth in [_viewing_history]. There we look at the -p and --stat option to get an idea of what was introduced in each commit and the --pretty and --oneline options to view the history more concisely, along with some simple date and author filtering options.
In [_create_new_branch] we use it with the --decorate option to easily visualize where our branch pointers are located and we also use the --graph option to see what divergent histories look like.
In [_private_team] and [_commit_ranges] we cover the branchA..branchB syntax to use the git log command to see what commits are unique to a branch relative to another branch. In [_commit_ranges] we go through this fairly extensively.
In [_merge_log] and [_triple_dot] we cover using the branchA…branchB format and the --left-right syntax to see what is in one branch or the other but not in both. In [_merge_log] we also look at how to use the --merge option to help with merge conflict debugging as well as using the --cc option to look at merge commit conflicts in your history.
In [_git_reflog] we use the -g option to view the Git reflog through this tool instead of doing branch traversal.
In [_searching] we look at using the -S and -L options to do fairly sophisticated searches for something that happened historically in the code such as seeing the history of a function.
In [_signing_commits] we see how to use --show-signature to add a validation string to each commit in the git log output based on if it was validly signed or not.
The git stash command is used to temporarily store uncommitted work in order to clean out your working directory without having to commit unfinished work on a branch.
This is basically entirely covered in [_git_stashing].
The git tag command is used to give a permanent bookmark to a specific point in the code history. Generally this is used for things like releases.
This command is introduced and covered in detail in [_git_tagging] and we use it in practice in [_tagging_releases].
We also cover how to create a GPG signed tag with the -s flag and verify one with the -v flag in [_signing].
There are not very many commands in Git that access the network, nearly all of the commands operate on the local database. When you are ready to share your work or pull changes from elsewhere, there are a handful of commands that deal with remote repositories.
The git fetch command communicates with a remote repository and fetches down all the information that is in that repository that is not in your current one and stores it in your local database.
We first look at this command in [_fetching_and_pulling] and we continue to see examples of it use in [_remote_branches].
We also use it in several of the examples in [_contributing_project].
We use it to fetch a single specific reference that is outside of the default space in [_pr_refs] and we see how to fetch from a bundle in [_bundling].
We set up highly custom refspecs in order to make git fetch do something a little different than the default in [_refspec].
The git pull command is basically a combination of the git fetch and git merge commands, where Git will fetch from the remote you specify and then immediately try to merge it into the branch you’re on.
We introduce it quickly in [_fetching_and_pulling] and show how to see what it will merge if you run it in [_inspecting_remote].
We also see how to use it to help with rebasing difficulties in [_rebase_rebase].
We show how to use it with a URL to pull in changes in a one-off fashion in [_checking_out_remotes].
Finally, we very quickly mention that you can use the --verify-signatures option to it in order to verify that commits you are pulling have been GPG signed in [_signing_commits].
The git push command is used to communicate with another repository, calculate what your local database has that the remote one does not, and then pushes the difference into the other repository. It requires write access to the other repository and so normally is authenticated somehow.
We first look at the git push command in [_pushing_remotes]. Here we cover the basics of pushing a branch to a remote repository. In [_pushing_branches] we go a little deeper into pushing specific branches and in [_tracking_branches] we see how to set up tracking branches to automatically push to. In [_delete_branches] we use the --delete flag to delete a branch on the server with git push.
Throughout [_contributing_project] we see several examples of using git push to share work on branches through multiple remotes.
We see how to use it to share tags that you have made with the --tags option in [_sharing_tags].
In [_publishing_submodules] we use the --recurse-submodules option to check that all of our submodules work has been published before pushing the superproject, which can be really helpful when using submodules.
In [_other_client_hooks] we talk briefly about the pre-push hook, which is a script we can setup to run before a push completes to verify that it should be allowed to push.
Finally, in [_pushing_refspecs] we look at pushing with a full refspec instead of the general shortcuts that are normally used. This can help you be very specific about what work you wish to share.
The git remote command is a management tool for your record of remote repositories. It allows you to save long URLs as short handles, such as `origin'' so you don’t have to type them out all the time. You can have several of these and the `git remote command is used to add, change and delete them.
This command is covered in detail in [_remote_repos], including listing, adding, removing and renaming them.
It is used in nearly every subsequent chapter in the book too, but always in the standard git remote add <name> <url> format.
The git archive command is used to create an archive file of a specific snapshot of the project.
We use git archive to create a tarball of a project for sharing in [_preparing_release].
The git submodule command is used to manage external repositories within a normal repositories. This could be for libraries or other types of shared resources. The submodule command has several sub-commands (add, update, sync, etc) for managing these resources.
This command is only mentioned and entirely covered in [_git_submodules].
The git show command can show a Git object in a simple and human readable way. Normally you would use this to show the information about a tag or a commit.
We first use it to show annotated tag information in [_annotated_tags].
Later we use it quite a bit in [_revision_selection] to show the commits that our various revision selections resolve to.
One of the more interesting things we do with git show is in [_manual_remerge] to extract specific file contents of various stages during a merge conflict.
The git shortlog command is used to summarize the output of git log. It will take many of the same options that the git log command will but instead of listing out all of the commits it will present a summary of the commits grouped by author.
We showed how to use it to create a nice changelog in [_the_shortlog].
The git describe command is used to take anything that resolves to a commit and produces a string that is somewhat human-readable and will not change. It’s a way to get a description of a commit that is as unambiguous as a commit SHA-1 but more understandable.
We use git describe in [_build_number] and [_preparing_release] to get a string to name our release file after.
Git has a couple of commands that are used to help debug an issue in your code. This ranges from figuring out where something was introduced to figuring out who introduced it.
The git bisect tool is an incredibly helpful debugging tool used to find which specific commit was the first one to introduce a bug or problem by doing an automatic binary search.
It is fully covered in [_binary_search] and is only mentioned in that section.
The git blame command annotates the lines of any file with which commit was the last one to introduce a change to each line of the file and what person authored that commit. This is helpful in order to find the person to ask for more information about a specific section of your code.
It is covered in [_file_annotation] and is only mentioned in that section.
The git grep command can help you find any string or regular expression in any of the files in your source code, even older versions of your project.
It is covered in [_git_grep] and is only mentioned in that section.
A few commands in Git are centered around the concept of thinking of commits in terms of the changes they introduce, as though the commit series is a series of patches. These commands help you manage your branches in this manner.
The git cherry-pick command is used to take the change introduced in a single Git commit and try to re-introduce it as a new commit on the branch you’re currently on. This can be useful to only take one or two commits from a branch individually rather than merging in the branch which takes all the changes.
Cherry picking is described and demonstrated in [_rebase_cherry_pick].
The git rebase command is basically an automated cherry-pick. It determines a series of commits and then cherry-picks them one by one in the same order somewhere else.
Rebasing is covered in detail in [_rebasing], including covering the collaborative issues involved with rebasing branches that are already public.
We use it in practice during an example of splitting your history into two separate repositories in [_replace], using the --onto flag as well.
We go through running into a merge conflict during rebasing in [_rerere].
We also use it in an interactive scripting mode with the -i option in [_changing_multiple].
The git revert command is essentially a reverse git cherry-pick. It creates a new commit that applies the exact opposite of the change introduced in the commit you’re targeting, essentially undoing or reverting it.
We use this in [_reverse_commit] to undo a merge commit.
Many Git projects, including Git itself, are entirely maintained over mailing lists. Git has a number of tools built into it that help make this process easier, from generating patches you can easily email to applying those patches from an email box.
The git apply command applies a patch created with the git diff or even GNU diff command. It is similar to what the patch command might do with a few small differences.
We demonstrate using it and the circumstances in which you might do so in [_patches_from_email].
The git am command is used to apply patches from an email inbox, specifically one that is mbox formatted. This is useful for receiving patches over email and applying them to your project easily.
We covered usage and workflow around git am in [_git_am] including using the --resolved, -i and -3 options.
There are also a number of hooks you can use to help with the workflow around git am and they are all covered in [_email_hooks].
We also use it to apply patch formatted GitHub Pull Request changes in [_email_notifications].
The git format-patch command is used to generate a series of patches in mbox format that you can use to send to a mailing list properly formatted.
We go through an example of contributing to a project using the git format-patch tool in [_project_over_email].
The git send-email command is used to send patches that are generated with git format-patch over email.
We go through an example of contributing to a project by sending patches with the git send-email tool in [_project_over_email].
The git request-pull command is simply used to generate an example message body to email to someone. If you have a branch on a public server and want to let someone know how to integrate those changes without sending the patches over email, you can run this command and send the output to the person you want to pull the changes in.
We demonstrate how to use git request-pull to generate a pull message in [_public_project].
Git comes with a few commands to integrate with other version control systems.
The git svn command is used to communicate with the Subversion version control system as a client. This means you can use Git to checkout from and commit to a Subversion server.
This command is covered in depth in [_git_svn].
For other version control systems or importing from nearly any format, you can use git fast-import to quickly map the other format to something Git can easily record.
This command is covered in depth in [_custom_importer].
If you’re administering a Git repository or need to fix something in a big way, Git provides a number of administrative commands to help you out.
The git gc command runs ``garbage collection'' on your repository, removing unnecessary files in your database and packing up the remaining files into a more efficient format.
This command normally runs in the background for you, though you can manually run it if you wish. We go over some examples of this in [_git_gc].
The git fsck command is used to check the internal database for problems or inconsistencies.
We only quickly use this once in [_data_recovery] to search for dangling objects.
The git reflog command goes through a log of where all the heads of your branches have been as you work to find commits you may have lost through rewriting histories.
We cover this command mainly in [_git_reflog], where we show normal usage to and how to use git log -g to view the same information with git log output.
We also go through a practical example of recovering such a lost branch in [_data_recovery].
The git filter-branch command is used to rewrite loads of commits according to certain patterns, like removing a file everywhere or filtering the entire repository down to a single subdirectory for extracting a project.
In [_removing_file_every_commit] we explain the command and explore several different options such as --commit-filter, --subdirectory-filter and --tree-filter.
In [_git_p4] and [_git_tfs] we use it to fix up imported external repositories.
There were also quite a number of lower level plumbing commands that we encountered in the book.
The first one we encounter is ls-remote in [_pr_refs] which we use to look at the raw references on the server.
We use ls-files in [_manual_remerge], [_rerere] and [_the_index] to take a more raw look at what your staging area looks like.
We also mention rev-parse in [_branch_references] to take just about any string and turn it into an object SHA-1.
However, most of the low level plumbing commands we cover are in [_git_internals], which is more or less what the chapter is focused on. We tried to avoid use of them throughout most of the rest of the book.