gitfaq

GITFAQ(7)                          Git Manual                          GITFAQ(7)



NAME
       gitfaq - Frequently asked questions about using Git

SYNOPSIS
       gitfaq

DESCRIPTION
       The examples in this FAQ assume a standard POSIX shell, like bash or
       dash, and a user, A U Thor, who has the account author on the hosting
       provider git.example.org.

CONFIGURATION
       What should I put in user.name?
           You should put your personal name, generally a form using a given
           name and family name. For example, the current maintainer of Git uses
           "Junio C Hamano". This will be the name portion that is stored in
           every commit you make.

           This configuration doesn’t have any effect on authenticating to
           remote services; for that, see credential.username in git-config(1).

       What does http.postBuffer really do?
           This option changes the size of the buffer that Git uses when pushing
           data to a remote over HTTP or HTTPS. If the data is larger than this
           size, libcurl, which handles the HTTP support for Git, will use
           chunked transfer encoding since it isn’t known ahead of time what the
           size of the pushed data will be.

           Leaving this value at the default size is fine unless you know that
           either the remote server or a proxy in the middle doesn’t support
           HTTP/1.1 (which introduced the chunked transfer encoding) or is known
           to be broken with chunked data. This is often (erroneously) suggested
           as a solution for generic push problems, but since almost every
           server and proxy supports at least HTTP/1.1, raising this value
           usually doesn’t solve most push problems. A server or proxy that
           didn’t correctly support HTTP/1.1 and chunked transfer encoding
           wouldn’t be that useful on the Internet today, since it would break
           lots of traffic.

           Note that increasing this value will increase the memory used on
           every relevant push that Git does over HTTP or HTTPS, since the
           entire buffer is allocated regardless of whether or not it is all
           used. Thus, it’s best to leave it at the default unless you are sure
           you need a different value.

       How do I configure a different editor?
           If you haven’t specified an editor specifically for Git, it will by
           default use the editor you’ve configured using the VISUAL or EDITOR
           environment variables, or if neither is specified, the system default
           (which is usually vi). Since some people find vi difficult to use or
           prefer a different editor, it may be desirable to change the editor
           used.

           If you want to configure a general editor for most programs which
           need one, you can edit your shell configuration (e.g., ~/.bashrc or
           ~/.zshenv) to contain a line setting the EDITOR or VISUAL environment
           variable to an appropriate value. For example, if you prefer the
           editor nano, then you could write the following:

               export VISUAL=nano

           If you want to configure an editor specifically for Git, you can
           either set the core.editor configuration value or the GIT_EDITOR
           environment variable. You can see git-var(1) for details on the order
           in which these options are consulted.

           Note that in all cases, the editor value will be passed to the shell,
           so any arguments containing spaces should be appropriately quoted.
           Additionally, if your editor normally detaches from the terminal when
           invoked, you should specify it with an argument that makes it not do
           that, or else Git will not see any changes. An example of a
           configuration addressing both of these issues on Windows would be the
           configuration "C:\Program Files\Vim\gvim.exe" --nofork, which quotes
           the filename with spaces and specifies the --nofork option to avoid
           backgrounding the process.

CREDENTIALS
       How do I specify my credentials when pushing over HTTP?
           The easiest way to do this is to use a credential helper via the
           credential.helper configuration. Most systems provide a standard
           choice to integrate with the system credential manager. For example,
           Git for Windows provides the wincred credential manager, macOS has
           the osxkeychain credential manager, and Unix systems with a standard
           desktop environment can use the libsecret credential manager. All of
           these store credentials in an encrypted store to keep your passwords
           or tokens secure.

           In addition, you can use the store credential manager which stores in
           a file in your home directory, or the cache credential manager, which
           does not permanently store your credentials, but does prevent you
           from being prompted for them for a certain period of time.

           You can also just enter your password when prompted. While it is
           possible to place the password (which must be percent-encoded) in the
           URL, this is not particularly secure and can lead to accidental
           exposure of credentials, so it is not recommended.

       How do I read a password or token from an environment variable?
           The credential.helper configuration option can also take an arbitrary
           shell command that produces the credential protocol on standard
           output. This is useful when passing credentials into a container, for
           example.

           Such a shell command can be specified by starting the option value
           with an exclamation point. If your password or token were stored in
           the GIT_TOKEN, you could run the following command to set your
           credential helper:

               $ git config credential.helper \
                       '!f() { echo username=author; echo "password=$GIT_TOKEN"; };f'


       How do I change the password or token I’ve saved in my credential
       manager?
           Usually, if the password or token is invalid, Git will erase it and
           prompt for a new one. However, there are times when this doesn’t
           always happen. To change the password or token, you can erase the
           existing credentials and then Git will prompt for new ones. To erase
           credentials, use a syntax like the following (substituting your
           username and the hostname):

               $ echo url=https://author@git.example.org | git credential reject


       How do I use multiple accounts with the same hosting provider using HTTP?
           Usually the easiest way to distinguish between these accounts is to
           use the username in the URL. For example, if you have the accounts
           author and committer on git.example.org, you can use the URLs
           https://author@git.example.org/org1/project1.git and
           https://committer@git.example.org/org2/project2.git. This way, when
           you use a credential helper, it will automatically try to look up the
           correct credentials for your account. If you already have a remote
           set up, you can change the URL with something like git remote set-url
           origin https://author@git.example.org/org1/project1.git (see git-
           remote(1) for details).

       How do I use multiple accounts with the same hosting provider using SSH?
           With most hosting providers that support SSH, a single key pair
           uniquely identifies a user. Therefore, to use multiple accounts, it’s
           necessary to create a key pair for each account. If you’re using a
           reasonably modern OpenSSH version, you can create a new key pair with
           something like ssh-keygen -t ed25519 -f ~/.ssh/id_committer. You can
           then register the public key (in this case, ~/.ssh/id_committer.pub;
           note the .pub) with the hosting provider.

           Most hosting providers use a single SSH account for pushing; that is,
           all users push to the git account (e.g., git@git.example.org). If
           that’s the case for your provider, you can set up multiple aliases in
           SSH to make it clear which key pair to use. For example, you could
           write something like the following in ~/.ssh/config, substituting the
           proper private key file:

               # This is the account for author on git.example.org.
               Host example_author
                       HostName git.example.org
                       User git
                       # This is the key pair registered for author with git.example.org.
                       IdentityFile ~/.ssh/id_author
                       IdentitiesOnly yes
               # This is the account for committer on git.example.org.
               Host example_committer
                       HostName git.example.org
                       User git
                       # This is the key pair registered for committer with git.example.org.
                       IdentityFile ~/.ssh/id_committer
                       IdentitiesOnly yes

           Then, you can adjust your push URL to use git@example_author or
           git@example_committer instead of git@example.org (e.g., git remote
           set-url git@example_author:org1/project1.git).

COMMON ISSUES
       I’ve made a mistake in the last commit. How do I change it?
           You can make the appropriate change to your working tree, run git add
           <file> or git rm <file>, as appropriate, to stage it, and then git
           commit --amend. Your change will be included in the commit, and
           you’ll be prompted to edit the commit message again; if you wish to
           use the original message verbatim, you can use the --no-edit option
           to git commit in addition, or just save and quit when your editor
           opens.

       I’ve made a change with a bug and it’s been included in the main branch.
       How should I undo it?
           The usual way to deal with this is to use git revert. This preserves
           the history that the original change was made and was a valuable
           contribution, but also introduces a new commit that undoes those
           changes because the original had a problem. The commit message of the
           revert indicates the commit which was reverted and is usually edited
           to include an explanation as to why the revert was made.

       How do I ignore changes to a tracked file?
           Git doesn’t provide a way to do this. The reason is that if Git needs
           to overwrite this file, such as during a checkout, it doesn’t know
           whether the changes to the file are precious and should be kept, or
           whether they are irrelevant and can safely be destroyed. Therefore,
           it has to take the safe route and always preserve them.

           It’s tempting to try to use certain features of git update-index,
           namely the assume-unchanged and skip-worktree bits, but these don’t
           work properly for this purpose and shouldn’t be used this way.

           If your goal is to modify a configuration file, it can often be
           helpful to have a file checked into the repository which is a
           template or set of defaults which can then be copied alongside and
           modified as appropriate. This second, modified file is usually
           ignored to prevent accidentally committing it.

       I asked Git to ignore various files, yet they are still tracked
           A gitignore file ensures that certain file(s) which are not tracked
           by Git remain untracked. However, sometimes particular file(s) may
           have been tracked before adding them into the .gitignore, hence they
           still remain tracked. To untrack and ignore files/patterns, use git
           rm --cached <file/pattern> and add a pattern to .gitignore that
           matches the <file>. See gitignore(5) for details.

       How do I know if I want to do a fetch or a pull?
           A fetch stores a copy of the latest changes from the remote
           repository, without modifying the working tree or current branch. You
           can then at your leisure inspect, merge, rebase on top of, or ignore
           the upstream changes. A pull consists of a fetch followed immediately
           by either a merge or rebase. See git-pull(1).

MERGING AND REBASING
       What kinds of problems can occur when merging long-lived branches with
       squash merges?
           In general, there are a variety of problems that can occur when using
           squash merges to merge two branches multiple times. These can include
           seeing extra commits in git log output, with a GUI, or when using the
           ...  notation to express a range, as well as the possibility of
           needing to re-resolve conflicts again and again.

           When Git does a normal merge between two branches, it considers
           exactly three points: the two branches and a third commit, called the
           merge base, which is usually the common ancestor of the commits. The
           result of the merge is the sum of the changes between the merge base
           and each head. When you merge two branches with a regular merge
           commit, this results in a new commit which will end up as a merge
           base when they’re merged again, because there is now a new common
           ancestor. Git doesn’t have to consider changes that occurred before
           the merge base, so you don’t have to re-resolve any conflicts you
           resolved before.

           When you perform a squash merge, a merge commit isn’t created;
           instead, the changes from one side are applied as a regular commit to
           the other side. This means that the merge base for these branches
           won’t have changed, and so when Git goes to perform its next merge,
           it considers all of the changes that it considered the last time plus
           the new changes. That means any conflicts may need to be re-resolved.
           Similarly, anything using the ...  notation in git diff, git log, or
           a GUI will result in showing all of the changes since the original
           merge base.

           As a consequence, if you want to merge two long-lived branches
           repeatedly, it’s best to always use a regular merge commit.

       If I make a change on two branches but revert it on one, why does the
       merge of those branches include the change?
           By default, when Git does a merge, it uses a strategy called the
           recursive strategy, which does a fancy three-way merge. In such a
           case, when Git performs the merge, it considers exactly three points:
           the two heads and a third point, called the merge base, which is
           usually the common ancestor of those commits. Git does not consider
           the history or the individual commits that have happened on those
           branches at all.

           As a result, if both sides have a change and one side has reverted
           that change, the result is to include the change. This is because the
           code has changed on one side and there is no net change on the other,
           and in this scenario, Git adopts the change.

           If this is a problem for you, you can do a rebase instead, rebasing
           the branch with the revert onto the other branch. A rebase in this
           scenario will revert the change, because a rebase applies each
           individual commit, including the revert. Note that rebases rewrite
           history, so you should avoid rebasing published branches unless
           you’re sure you’re comfortable with that. See the NOTES section in
           git-rebase(1) for more details.

HOOKS
       How do I use hooks to prevent users from making certain changes?
           The only safe place to make these changes is on the remote repository
           (i.e., the Git server), usually in the pre-receive hook or in a
           continuous integration (CI) system. These are the locations in which
           policy can be enforced effectively.

           It’s common to try to use pre-commit hooks (or, for commit messages,
           commit-msg hooks) to check these things, which is great if you’re
           working as a solo developer and want the tooling to help you.
           However, using hooks on a developer machine is not effective as a
           policy control because a user can bypass these hooks with --no-verify
           without being noticed (among various other ways). Git assumes that
           the user is in control of their local repositories and doesn’t try to
           prevent this or tattle on the user.

           In addition, some advanced users find pre-commit hooks to be an
           impediment to workflows that use temporary commits to stage work in
           progress or that create fixup commits, so it’s better to push these
           kinds of checks to the server anyway.

CROSS-PLATFORM ISSUES
       I’m on Windows and my text files are detected as binary.
           Git works best when you store text files as UTF-8. Many programs on
           Windows support UTF-8, but some do not and only use the little-endian
           UTF-16 format, which Git detects as binary. If you can’t use UTF-8
           with your programs, you can specify a working tree encoding that
           indicates which encoding your files should be checked out with, while
           still storing these files as UTF-8 in the repository. This allows
           tools like git-diff(1) to work as expected, while still allowing your
           tools to work.

           To do so, you can specify a gitattributes(5) pattern with the
           working-tree-encoding attribute. For example, the following pattern
           sets all C files to use UTF-16LE-BOM, which is a common encoding on
           Windows:

               *.c     working-tree-encoding=UTF-16LE-BOM

           You will need to run git add --renormalize to have this take effect.
           Note that if you are making these changes on a project that is used
           across platforms, you’ll probably want to make it in a per-user
           configuration file or in the one in $GIT_DIR/info/attributes, since
           making it in a .gitattributes file in the repository will apply to
           all users of the repository.

           See the following entry for information about normalizing line
           endings as well, and see gitattributes(5) for more information about
           attribute files.

       I’m on Windows and git diff shows my files as having a ^M at the end.
           By default, Git expects files to be stored with Unix line endings. As
           such, the carriage return (^M) that is part of a Windows line ending
           is shown because it is considered to be trailing whitespace. Git
           defaults to showing trailing whitespace only on new lines, not
           existing ones.

           You can store the files in the repository with Unix line endings and
           convert them automatically to your platform’s line endings. To do
           that, set the configuration option core.eol to native and see the
           following entry for information about how to configure files as text
           or binary.

           You can also control this behavior with the core.whitespace setting
           if you don’t wish to remove the carriage returns from your line
           endings.

       Why do I have a file that’s always modified?
           Internally, Git always stores file names as sequences of bytes and
           doesn’t perform any encoding or case folding. However, Windows and
           macOS by default both perform case folding on file names. As a
           result, it’s possible to end up with multiple files or directories
           whose names differ only in case. Git can handle this just fine, but
           the file system can store only one of these files, so when Git reads
           the other file to see its contents, it looks modified.

           It’s best to remove one of the files such that you only have one
           file. You can do this with commands like the following (assuming two
           files AFile.txt and afile.txt) on an otherwise clean working tree:

               $ git rm --cached AFile.txt
               $ git commit -m 'Remove files conflicting in case'
               $ git checkout .

           This avoids touching the disk, but removes the additional file. Your
           project may prefer to adopt a naming convention, such as
           all-lowercase names, to avoid this problem from occurring again; such
           a convention can be checked using a pre-receive hook or as part of a
           continuous integration (CI) system.

           It is also possible for perpetually modified files to occur on any
           platform if a smudge or clean filter is in use on your system but a
           file was previously committed without running the smudge or clean
           filter. To fix this, run the following on an otherwise clean working
           tree:

               $ git add --renormalize .


       What’s the recommended way to store files in Git?
           While Git can store and handle any file of any type, there are some
           settings that work better than others. In general, we recommend that
           text files be stored in UTF-8 without a byte-order mark (BOM) with LF
           (Unix-style) endings. We also recommend the use of UTF-8 (again,
           without BOM) in commit messages. These are the settings that work
           best across platforms and with tools such as git diff and git merge.

           Additionally, if you have a choice between storage formats that are
           text based or non-text based, we recommend storing files in the text
           format and, if necessary, transforming them into the other format.
           For example, a text-based SQL dump with one record per line will work
           much better for diffing and merging than an actual database file.
           Similarly, text-based formats such as Markdown and AsciiDoc will work
           better than binary formats such as Microsoft Word and PDF.

           Similarly, storing binary dependencies (e.g., shared libraries or JAR
           files) or build products in the repository is generally not
           recommended. Dependencies and build products are best stored on an
           artifact or package server with only references, URLs, and hashes
           stored in the repository.

           We also recommend setting a gitattributes(5) file to explicitly mark
           which files are text and which are binary. If you want Git to guess,
           you can set the attribute text=auto. For example, the following might
           be appropriate in some projects:

               # By default, guess.
               *       text=auto
               # Mark all C files as text.
               *.c     text
               # Mark all JPEG files as binary.
               *.jpg   binary

           These settings help tools pick the right format for output such as
           patches and result in files being checked out in the appropriate line
           ending for the platform.

GIT
       Part of the git(1) suite



Git 2.30.0                         12/28/2020                          GITFAQ(7)