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?

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?

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 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?

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?

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 \
\n
        '!f() { echo username=author; echo "password=$GIT_TOKEN"; };f'

How do I change the password or token I’ve saved in my credential manager?

$ echo url=https://[email protected] | git credential reject

How do I use multiple accounts with the same hosting provider using HTTP?

How do I use multiple accounts with the same hosting provider using SSH?

Most hosting providers use a single SSH account for pushing; that is, all users push to the git account (e.g., [email protected]). 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
\n
        HostName git.example.org
\n
        User git
\n
        # This is the key pair registered for author with git.example.org.
\n
        IdentityFile ~/.ssh/id_author
\n
        IdentitiesOnly yes
# This is the account for committer on git.example.org.
Host example_committer
\n
        HostName git.example.org
\n
        User git
\n
        # This is the key pair registered for committer with git.example.org.
\n
        IdentityFile ~/.ssh/id_committer
\n
        IdentitiesOnly yes

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

TRANSFERS#

How do I sync a working tree across systems?

Usually, doing so will cause git status to need to re-read every file in the working tree. Additionally, Git’s security model does not permit sharing a working tree across untrusted users, so it is only safe to sync a working tree if it will only be used by a single user across all machines.

It is important not to use a cloud syncing service to sync any portion of a Git repository, since this can cause corruption, such as missing objects, changed or added files, broken refs, and a wide variety of other problems. These services tend to sync file by file on a continuous basis and don’t understand the structure of a Git repository. This is especially bad if they sync the repository in the middle of it being updated, since that is very likely to cause incomplete or partial updates and therefore data loss.

An example of the kind of corruption that can occur is conflicts over the state of refs, such that both sides end up with different commits on a branch that the other doesn’t have. This can result in important objects becoming unreferenced and possibly pruned by git gc, causing data loss.

Therefore, it’s better to push your work to either the other system or a central server using the normal push and pull mechanism. However, this doesn’t always preserve important data, like stashes, so some people prefer to share a working tree across systems.

If you do this, the recommended approach is to use rsync -a --delete-after (ideally with an encrypted connection such as with ssh) on the root of repository. You should ensure several things when you do this:

Be aware that even with these recommendations, syncing in this way has some risk since it bypasses Git’s normal integrity checking for repositories, so having backups is advised. You may also wish to do a git fsck to verify the integrity of your data on the destination system after syncing.

COMMON ISSUES#

I’ve made a mistake in the last commit. How do I change it?

I’ve made a change with a bug and it’s been included in the main branch. How should I undo it?

How do I ignore changes to a tracked file?

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

How do I know if I want to do a fetch or a pull?

Can I use a proxy with Git?

For SSH, Git can support a proxy using OpenSSH’s ProxyCommand. Commonly used tools include netcat and socat. However, they must be configured not to exit when seeing EOF on standard input, which usually means that netcat will require -q and socat will require a timeout with something like -t 10. This is required because the way the Git SSH server knows that no more requests will be made is an EOF on standard input, but when that happens, the server may not have yet processed the final request, so dropping the connection at that point would interrupt that request.

An example configuration entry in ~/.ssh/config with an HTTP proxy might look like this:

Host git.example.org
\n
    User git
\n
    ProxyCommand socat -t 10 - PROXY:proxy.example.org:%h:%p,proxyport=8080

Note that in all cases, for Git to work properly, the proxy must be completely transparent. The proxy cannot modify, tamper with, or buffer the connection in any way, or Git will almost certainly fail to work. Note that many proxies, including many TLS middleboxes, Windows antivirus and firewall programs other than Windows Defender and Windows Firewall, and filtering proxies fail to meet this standard, and as a result end up breaking Git. Because of the many reports of problems and their poor security history, we recommend against the use of these classes of software and devices.

MERGING AND REBASING#

What kinds of problems can occur when merging long-lived branches with squash merges?

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?

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?

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.

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.

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 question on recommended storage settings 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?

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?

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.

With text files, Git will generally ensure that LF endings are used in the repository. The core.autocrlf and core.eol configuration variables specify what line-ending convention is followed when any text file is checked out. You can also use the eol attribute (e.g., eol=crlf) to override which files get what line-ending treatment.

For example, generally shell files must have LF endings and batch files must have CRLF endings, so the following might be appropriate in some projects:

# By default, guess.
*       text=auto
# Mark all C files as text.
*.c     text
# Ensure all shell files have LF endings and all batch files have CRLF
# endings in the working tree and both have LF in the repo.
*.sh text eol=lf
*.bat text eol=crlf
# 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